the presentation encompasses auxin synthesis, conjugation, degradation, polar and lateral transport and signalling and how all of these together have a bearing on programming and design of the whole plant
The biosynthesis of the main auxin in plants (indole-3-acetic acid [IAA]) has been elucidated recently and is thought to involve the sequential conversion of Trp to indole-3-pyruvic acid to IAA. However, the pathway leading to a less well studied auxin, phenylacetic acid (PAA), remains unclear. Here, we present evidence from metabolism experiments that PAA is synthesized from the amino acid Phe, via phenylpyruvate. In pea (Pisum sativum), the reverse reaction, phenylpyruvate to Phe, is also demonstrated. However, despite similarities between the pathways leading to IAA and PAA, evidence from mutants in pea and maize (Zea mays) indicate that IAA biosynthetic enzymes are not the main enzymes for PAA biosynthesis. Instead, we identified a putative aromatic aminotransferase (PsArAT) from pea that may function in the PAA synthesis pathway.
The biosynthesis of the main auxin in plants (indole-3-acetic acid [IAA]) has been elucidated recently and is thought to involve the sequential conversion of Trp to indole-3-pyruvic acid to IAA. However, the pathway leading to a less well studied auxin, phenylacetic acid (PAA), remains unclear. Here, we present evidence from metabolism experiments that PAA is synthesized from the amino acid Phe, via phenylpyruvate. In pea (Pisum sativum), the reverse reaction, phenylpyruvate to Phe, is also demonstrated. However, despite similarities between the pathways leading to IAA and PAA, evidence from mutants in pea and maize (Zea mays) indicate that IAA biosynthetic enzymes are not the main enzymes for PAA biosynthesis. Instead, we identified a putative aromatic aminotransferase (PsArAT) from pea that may function in the PAA synthesis pathway.
Presentation for Plant Physiology. I was in charge of creating and designing the presentation as well as formating the images and information. Our projec won our class competition in regards to overall look and presentation.
Gibberellins: Discovery, Biosynthesis, Function and RegulationAhmed Aquib
Gibberellins (GAs) are plant hormones that regulate various developmental processes, including stem elongation, germination, dormancy, flowering, flower development, and leaf and fruit senescence. GAs are one of the longest-known classes of plant hormone. I have discussed Discovery, Biosynthesis, Function and Regulation of Gibberellins in detail
Plant hormones are naturally occurring organic substances that affect physiological processes. There are five major groups of plant hormones, such as auxins, gibberellins, cytokinins, abscisic acid and ethylene. In this presentation deals with Cytokinins with its biosynthesis, transport, pathways and physiological effects.
Plant hormones are naturally occurring organic substances that affect physiological processes. There are five major groups of plant hormones, such as auxins, gibberellins, cytokinins, abscisic acid and ethylene. In this presentation auxin is described with its biosynthesis, transport, pathways and physiological effects.
Plant hormones are naturally occurring organic substances that affect physiological processes. There are five major groups of plant hormones, such as auxins, gibberellins, cytokinins, abscisic acid and ethylene. In this presentation gibberellins is described with its biosynthesis, transport and physiological effects.
Presentation for Plant Physiology. I was in charge of creating and designing the presentation as well as formating the images and information. Our projec won our class competition in regards to overall look and presentation.
Gibberellins: Discovery, Biosynthesis, Function and RegulationAhmed Aquib
Gibberellins (GAs) are plant hormones that regulate various developmental processes, including stem elongation, germination, dormancy, flowering, flower development, and leaf and fruit senescence. GAs are one of the longest-known classes of plant hormone. I have discussed Discovery, Biosynthesis, Function and Regulation of Gibberellins in detail
Plant hormones are naturally occurring organic substances that affect physiological processes. There are five major groups of plant hormones, such as auxins, gibberellins, cytokinins, abscisic acid and ethylene. In this presentation deals with Cytokinins with its biosynthesis, transport, pathways and physiological effects.
Plant hormones are naturally occurring organic substances that affect physiological processes. There are five major groups of plant hormones, such as auxins, gibberellins, cytokinins, abscisic acid and ethylene. In this presentation auxin is described with its biosynthesis, transport, pathways and physiological effects.
Plant hormones are naturally occurring organic substances that affect physiological processes. There are five major groups of plant hormones, such as auxins, gibberellins, cytokinins, abscisic acid and ethylene. In this presentation gibberellins is described with its biosynthesis, transport and physiological effects.
Biological membranes as a barriers to drugs(pH trapping)Freya Cardozo
Transport of drugs across the membrane, Passive Diffusion, carrier mediated, Facilitated, Endocytosis, Ion transport and pH trapping.
Blood brain barrier and(BBB) stratergies to overcome BBB
Transcription factors of the nuclear factor κ B family are the paradigm for signaling dependent nuclear translocation and are ideally suited to analysis through image-based chemical genetic screening. The authors describe combining high-content image analysis with a compound screen to identify compounds affecting either nuclear import or export. Validation in silico and in vitro determined an EC50 for the nuclear export blocker leptomycin B of 2.4 ng/mL (4.4 nM). The method demonstrated high selectivity (Z′ >0.95), speed, and robustness in a screen of a compound collection. It identified the IκB protein kinase inhibitor BAY 11 7082 as an import inhibitor, the p38 mitogen-activated protein (MAP) kinase inhibitor PD98509 as an import enhancer, and phorbol ester as an export inhibitor. The results establish a robust method for identifying compounds regulating nucleocy- toplasmic import or export and also implicate MAP kinases in nuclear import of nuclear factor κ B
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
1. SUDERSHAN MISHRA (51063)
M.Sc. (Ag) Previous
Deptt. Of Plant Physiology
College of Basic Sciences and Humanities
GBPUA&T, Pantnagar, US Nagar.
A MORPHOGEN IN
PLANT GROWTH AND DEVELOPMENT
3. Discovery of auxin
Actions of auxin
Approaches for dissecting mechanisms of auxin action
3 pillars of morphogenic functionality of auxins
PIN trafficking
Foremost action of auxin- cell elongation
Lateral redistribution of auxins and tropic movements
Morphogenic effects of auxin
Case study
Conclusion
3
4. Fig-1a Early experiments in auxin research
A. From experiments
on coleoptile photo-
tropism, Darwin
concluded in 1880 that
a growth stimulus is
produced in the
coleoptile tip and is
transmitted to the
growth zone.
B. In 1913, P. Boysen-
Jensen discovered that
the growth stimulus
passes through gelatin
but not through water-
impermeable barriers
such as mica.
4
5. Fig-1b Early experiments in auxin research
A. In 1926, F. W. Went
showed that the active
growth promoting
substance can diffuse
into a gelatin block.
B. He also devised a
coleoptile- bending
assay for quantitative
auxin analysis.
5
6. Auxin- The Growth Hormone
Fig-2 Auxin stimulates the elongation of oat coleoptile sections. These
coleoptile sections were incubated for 18 hours in either water (A) or auxin (B)
6
7. Actions of Auxins
CELL
ELONGATION
Growth of Stem
Growth of coleoptiles
Growth of roots
PLANT TROPISMS
Phototropism
Gravitropism
Thigmotropism
DEVELOPMENTAL
EFFECTS
Apical Dominance
Floral Bud Development&
Phyllotaxy
Arrangement of RAM and
SAM
Adventitious root
development
Vascular Differentiation
Role in Abscission
Fruit Development
7
8. Method Sensitivity Specificity Resolution Comments
Mass Spectroscopy-
Molecules identified based
on mass and charge
Medium High Tissue or
organ
L:evel
Can discriminate
between different forms
of Auxin
Immunodetection-
Antibodies recognize
molecules having a specific
confirmation
High Medium Cellular Sensitivity depends on
the accessibility of auxin
to antibody and
specificity of antibody
Reporters- Auxin activated
promoter fused to gene that
produces a visible readout
High High Cellular A transcription-based
synthetic reporter, DR5,
consisting of multiple
tandem repeats of ARF
binding site (TGTCTC)
fused with GFP is used
commonly
Screens- Identification and
characterization of mutants
resistant to exogenous auxin
and auxin polar transport
inhibitors.
High High Cellular
and sub-
cellular
auxin-resistant mutants
at eight loci (aux1; axr1,
2, 4, 5, and 6; Dwf; and
tir1) have been isolated
Approaches used for dissecting mechanisms
of auxin action
Table-1 Various approaches to dissect mechanisms of
auxin action
8
9. Approaches used ………….(Contd.)
Developing Reporters Mutant Screens
Analysis of the promoter regions of
auxin inducible genes
Identify the transcription factors
binding to the AuxREs
Identify the conserved elements: e.g.
TGTCTC
Fuse multiple copies of the conserved
elements to visible readout signal like
GFP or GUS
Auxin-resistant mutants at eight loci
(aux1; axr1, 2, 4, 5, and 6; Dwf; and
tir1) have been isolated by their ability
to elongate roots on normally
prohibitive concentrations of auxin
9
10. AUXIN HOMEOSTASIS
BIOSYNTHESIS , CONJUGATION AND DEGRADATION
AUXIN TRANSPORT
POLAR, AND REDISTRIBUTIONARY , PIN TRAFFICKING
AUXIN SIGNALLING
3 Pillars of Morphogenic Functionality of
Auxin
10
15. Auxin Transport- Polar transport of Auxin is
gravity independent
Fig-4a Simple experiment to demonstrate that polarity of
auxin transport is independent of gravity
Fig-4b Roots grow from the
basal ends of these bamboo
sections, even when they are
inverted. The roots form at
the basal end because polar
auxin transport in the shoot
is independent of gravity
15
16. Auxin Transport- Chemiosmotic mechanism
of polar auxin transport
AUXIN INFLUX
Passive diffusion of the protonated
(IAAH) form across the phospholipid
bilayer
Secondary active transport of the
dissociated (IAA–) form via a 2H+–IAA–
symporter
These symporters are a family of
AUX/LAX permeases related to bacterial
amino acid carriers
This is saturable and specific for active
auxins
AUXIN EFFLUX
Most of the Auxin
escapes via auxin
anion efflux carrier
A family of putative
auxin efflux carriers
known as PIN
proteins (named
after the pin-shaped
inflorescences
formed by the pin1
mutant of
Arabidopsis are
localized precisely at
the basal ends of the
conducting cells
Fig-4c pin1
mutant of
Arabidopsis
16
17. Chemiosmotic mechanism……..(Contd)
Fig- 4d The repetition of auxin uptake
at the apical end of the cell and
preferential release from the base of
each cell in the pathway gives rise to the
total polar transport effect.
17
18. Integrated model of polar auxin transport
Fig-4e Schematic representation
of Polar auxin transport
In addition to the well known
AUX1/LAX and PIN family proteins
it includes a family of ATP
dependent transporters
These are ‘P’ glycoproteins or ‘B’
subclass of the large ABC family of
integral membrane transporters
Hence a subgroup of PGP/ABCB
transporters function as ATP
dependent amphipathic auxin
anion efflux carriers
ABCBs are uniformly distributed
rather than polarly however PINs
function synergistically with ABCB
in polar auxin transport
Certain tonoplast carriers like
ZIFL1.1 help in stabilizing PIN
proteins particularly pin 2
18
19. Phloem mediated non-polar auxin transport
Fig-4f Asymmetric localization
of AUX1 in a file of protophloem
cells
The asymmetrically oriented AUX1
permease promotes the acropetal
movement of auxin from the
phloem to the root apex
The phloem appears to represent
the principal pathway for long-
distance auxin translocation to the
root.
Long-distance auxin transport in
the phloem is important for
controlling such processes as
cambial cell divisions, callose
accumulation or removal from
sieve tube elements, and branch
root formation.
Polar and non polar transport are
not independent of each other and
can be exchanged at shoot apices
19
20. Subcellular polarity of PINs determine the direction of auxin efflux out of that
cell and thus coordinated PIN localizations along the chain of cells channelize
directionality of auxin transport.
PINs are not statically localized at the plasma membrane but undergo rapid
clathrin mediated endocytic cycling involving PIN internalization from plasma
membrane
They are recycled back to plasma membrane via ARF-GEF (GNOM) regulated
polar cycling
The protein kinase PINOID and protein phosphatase 2A complex RCN1 are
also involved in regulating this PIN trafficking
Auxin efflux inhibitors like TIBA, NPA and certain flavonols affect this
trafficking
PIN trafficking and localization with respect
to directionality of auxin transport
20
21. A B C
D E
Fig-4g (A) Control, showing
asymmetric localization of PIN1.
(B) After treatment with brefeldin
A(BFA). (C) Following an
additional two-hour washout of
BFA. (D) Following a BFA
washout with cytochalasin D.
(E) Following a BFAwashout with
the auxin transport inhibitor
TIBA.
PIN trafficking and localization…..(Contd.)
21
22. PIN trafficking and localization…..(Contd.)
Fig-4i Actin dependent pin
cycling between plasma
membrane and an endosomal
compartment
Fig-4h mechanism of
establishment of PIN polarity by
AGC-3 Kinases
22
23. Auxin Signalling
Proteins of TIR1/AFB family are the principle auxin receptors
They are F-box protein components of an SCF-ubiquitin E3 ligase complex
(SCFTIR1/AFB)that catalyzes the ATP dependent covalent addition of Ubiquitin
molecules to proteins targeted for proteolytic degradation
Auxin acts as a molecular glue to bring together a heterodimer consisting of
one TIR1/AFB and one AUX/IAA protein
AUX/IAA proteins are one of the two families of transcriptional regulators,
the other being the ARFs. Both are antagonists to each other. If the ARF in
question is a transcriptional activator, the corresponding AUX/IAA protein
will act as repressor
ARFs are short lived nuclear proteins that bind DNA AuxREs containing the
consensus sequence TGTCTC in promoters of auxin response genes
AUX/IAA bind to ARF proteins bound to DNA
23
25. Foremost effect of auxin- cell elongation
Auxin Rapidly Increases the Extensibility
of the Cell Wall
The effects of various parameters on the
growth rate are encapsulated in the
growth rate equation:
GR = m (ψp – Y)
Where GR is the growth rate, Yp is the
turgor pressure, Y is the yield threshold,
and m is the coefficient (wall
extensibility) that relates the growth
rate to the difference between ψp and Y.
Auxin-Induced proton extrusion
acidifies the cell wall and increases cell
extension. This proton extrusion my
involve both activation as well as
synthesis of plasma membrane H+ -
ATPases.
ABPs and Expansin proteins are involved
Fig-6Kinetics of auxin-induced elongation
and cell wall acidification in maize
coleoptiles. The pH of the cell wall was
measured with a pH microelectrode. Note
the similar lag times (10 to 15 minutes) for
both cell wall acidification
and the increase in the rate of elongation
25
26. Lateral redistribution of auxins- the primary
cause of plant tropisms
Fig-7 Evidence that the lateral redistribution of auxin is stimulated by unidirectional
light in corn coleoptiles
26
27. Lateral redistribution …….plant tropisms
(Contd.)
Fig-8 Visualization of lateral redistribution using A and B Agar blocks C.. DR5::GUS
reporter gene construct
(c)
27
28. Fig-9 Statoliths and Redistribution of auxin during gravitropism in
maize roots
Lateral redistribution …….plant tropisms
(Contd.)
28
29. Commencement of polarized auxin transport in globular embryo might
facilitate the morphological polarity expressed in subsequent stages of plant
embryogenesis
Once the first division of zygote is over, PIN7 is confined to the apical side of
the basal cell driving auxin transport into apical cell
At 32 cell phase PIN7 polarity reverses to the basal membrane of the
suspensor cells
PIN4 regulates transport in hypophysis while PIN 3 in columella precursors
Single pin mutant dosen’t display darmatic effects but miltiple pin mutants
show severe root and shoot pole defects
Auxin as a morphogen during
embryogenesis
29
30. Auxin……….embryogenesis (contd.)
Fig-11 Polar-localized auxin efflux carrier PIN proteins direct auxin flow
during embryogenesis and root meristem growth to generate local auxin
accumulation foci responsible for organ growth
Fig-10 Immunolocalization
of AUX1 in protophloem
cells of the stele, a central
cluster of cells in the
columella, and
lateral root cap cells
30
31. Auxin……….embryogenesis (contd.)
Fig-12 Genes whose functions are essential for Arabidopsis
embryogenesis
A. GNOM (GN)
Encodes a guanine
nucleotide exchange
factor (GEF) which
enables polar
distribution of auxin
by establishing a
polar distribution of
PIN efflux carriers
B. MONOPTEROS (MP)-
necessary for the
normal formation of
basal elements such
as the root and
hypocotyl , encodes
and auxin response
factor
31
32. Auxin and shoot morphogenesis
Auxin is sufficient in itself to trigger organ initiation when applied at the tip
of naked meristem of pin1mutant which is defective in polar auxin transport
Modular studies incorporating polar transport of the auxins and mechanical
strains suggest that auxin is transported to the site of lateral organ
primordia inception by polar auxin efflux carrier PIN1
Growing lateral organ primordium acts as sink and this leads to depletion of
auxin from surrounding cells, creating an inhibitory field which in turn
controls the spacing between lateral organs to define a specific phyllotactic
pattern.
Recently it has been shown that pin1 hypomorphs result in switch of spiral
pattern to opposite pattern (Prasad et al. 2011)
32
33. Auxin and shoot morphogenesis (Contd.)
Fig-13 Polar auxin transport based schematic representation of different patterns
arising at the shoot apex; (a) Distichous (alternate), (b) Spiral, (c) Decussate
(opposite) pattern. I (Incipient primordium), P (Primordium)
33
34. When the apical bud is grafted onto a
clump of undifferentiated cells, or
callus, xylem and phloem
differentiate beneath the graft.
The relative amounts of xylem and
phloem formed are regulated by the
auxin concentration: High auxin
concentrations induce the
differentiation of xylem and phloem,
but only phloem differentiates at low
auxin concentrations
The regeneration of vascular tissue
following wounding is also controlled
by auxin produced by the young leaf
directly above the wound site
Vascular differentiation is polar and
occurs from leaves to roots.
Auxin and Vascular Differentiation
Fig-14 Detection of sites of auxin
synthesis and transport in a young leaf
primordium of DR5 Arabidopsis by
means of a GUS reporter gene with an
auxin-sensitive promoter.
34
35. Auxin and Vascular Differentiation (Contd.)
Fig-15 IAA-induced xylem regeneration around the wound in cucumber (Cucumis
sativus) stem tissue. (A) Method for carrying out the wound regeneration experiment.
(B) Fluorescence micrograph showing regenerating vascular tissue
around the wound35
36. Auxin and Root Development
Although elongation of the
primary root is inhibited by
auxin concentrations greater
than 10–8 M, initiation of
lateral (branch) roots and
adventitious roots is
stimulated by high auxin levels
A series of Arabidopsis
mutants, named alf (aberrant
ateral root formation), have
provided some insights into
the role of auxin in the
initiation of lateral roots. The
alf1 mutant exhibits extreme
proliferation of adventitious
and lateral roots, coupled with
a 17-fold increase in
endogenous auxin
Fig-16 Root morphology of Arabidopsis (A–C) wild-type
and alf1 seedlings (D–F) on hormone-free medium. Note
the proliferation of root primordia growing from the
pericycle in the alf1 seedlings (D and E)36
37. Patterning an angiosperm flower requires
the combined and individual functions of
class A, B, C, D, and E MADS box
transcription factors
LOFSEP group of genes are specific to
grasses and contribute to panicle
morphology, spikelet and FM specification,
floral organ differentiation, and meristem
determinacy
Rice LEAFY HULL STERILE (LHS1)/OsMADS1,
a member of the grass subgroup of LOFSEP
genes, referred to henceforth as OsMADS1,
is expressed in FMs, functions during FM
establishment and floret organ patterning,
and contributes to meristem termination
Auxin as a morphogen in floral meristem
specification
Fig-17 OsMADS1 exerts its effects through
meristem regulators and activating auxin
signaling
37
38. Title- “Auxin Acts through MONOPTEROS to
Regulate Plant Cell Polarity and Pattern
Phyllotaxis”
Neha Bhatia, Behruz Bozorg, Andre´ Larsson, Carolyn Ohno, Henrik Jonsson,
Marcus G. Heisler
Case Study
38
39. Central idea of the study
Organ positioning in plants
depends on polar transport
of the hormone auxin to
organ initiation sites. The
auxin response factor
MONOPTEROS orients the
polarity of the auxin efflux
carrier PIN1 non-cell
autonomously, thereby
facilitating a positive
feedback loop that results in
periodic organ formation.
39
40. Auxin-regulated MP expression and activity predict
PIN1 polarity changes at the SAM
Localized MP activity is necessary to mediate periodic
organ formation
MP orients PIN1 polarity non-cell autonomously to
promote local auxin accumulation
Sub-epidermal MP activity is required to stabilize auxin
distribution patterns
Highlights of the study
40
42. Figure 18. MP Expression
Patterns Predict PIN1 Polarity
Changes
(A) pMP::MP-YPet (green) and
pPIN1::PIN1-CFP (magenta)
expression and localization in
the mp-T370 inflorescence
meristem (IM).
(B) Meristem in (A) showing
pPIN1::PIN1-CFP alone.
(C) Meristem in (A) showing
pMP::MP-YPet expression alone.
(D) Magnified view of i4 before
PIN1 polarity convergence.
(E) Magnified view of i3 after
PIN1 convergence.
(F) Magnified view of i1. Note
the low MP expression
surrounding i1 prior to PIN1
polarity reversal.
(G) Magnified view of P1
showing reduced MP expression
surrounding the primordium
and PIN1 polarity oriented away
from low-MP-expressing cells.
The arrows indicate the
estimated PIN1 polarity
direction within the cells.
Primordium (P) and incipient
primordium (i) stages are
numbered i4–P5
42
43. Figure 19. Localized Organogenesis
Requires
Localized MP Activity
(A) Wild-type seedling 18 days after
induction
of pUBQ10>>MPc794-YPet (dotted
rectangle) in
comparison to an un-induced plant.
(B) Magnified view of an induced
plant from (A).
Note the fusion of the first two
leaves.
(C–H) pPIN1::PIN1-CFP expression
and polarity
(green) after induction of
pUBQ10>>MPc794-Ypet
(I–K) pPIN1::PIN1-CFP expression and
polarity
(green) before (I) and after induction
of
pUBQ10>>MPc794-YPet (magenta) (J
and K) in
mp IM. Note the ring-shaped organ
present 5 days
after MPc794-YPet induction (K).
The asterisk in (C) marks the
removed cotyledon.
43
44. Figure 20. MP Polarizes Cells Non-Cell
Autonomously
(A and B) Confocal projection showing
the mp-B4149 apex expressing
pPIN1::PIN1-GFP (magenta) before (A)
and 8 days after induction of MP-YPet
clones (B) C) Frequency of peripheral
MP clones associated with PIN1
convergence patterns (n = 60
peripheral clones of MP). (D–M) Time
series showing epidermal MP-VENUS
clones in mp-T370 and associated
changes in PIN1-CFP localization.
(D–H) Overview showing two
independent clones. . (I–M) Magnified
view of the dotted rectangle in (D).
(N) Longitudinal optical section
showing a sub-epidermal polarity
response to the epidermal clone.
(O) Cross-section showing lateral PIN1
polarity toward the MP clone in the
sub-epidermal layer.
(P) PIN1-CFP convergence in the
epidermal cell layer in response to a
sub-epidermal MP clone.
(Q) Longitudinal reconstructed section
of (P) showing a sub-epidermal MP-
VENUS clone.
The arrows indicate the estimated PIN
polarity direction within the cells.
44
45. Figure 21. Restriction of MP Activity
to the Epidermis Results in Mobile
Auxin Maxima
(A and B) pML1::MP-YPet expression
(magenta) in wild-type before (A)
and 6 hr after auxin treatment (B) (n
> 20).
(C and D) pML1::2X-CFP-N7
expression (magenta) before (C) and
6 hr after auxin treatment (D) (n =
6).
(E) Photograph of the mp-T370
mutant expressing pML1::MP-YPet.
(F) Confocal projection of an mp-
T370 mutant seedling with fused
leaves (white arrowhead), with
pML1::MP-YPet (magenta) and
pPIN1::PIN1-CFP (green).
(G and H) IM of mp-T370
expressing pML1::MP-YPet;
photograph (G) and confocal
projection, with pML1::MP-YPet
(magenta) and pPIN1::PIN1-CFP
(green) (H).
(I) Magnified view of the dotted
rectangle in
(J and K) Time series of mp-T370
IMs expressing pML1::MP-YPet and
pPIN1::PIN1-CFP before (J) and 12 hr
later (K). (L) or the absence thereof
(M).
45
47. Fig- 22 Cross-regulatory interactions of different phytohormones
with auxin for understanding the intricacies involved in plant root
development.47
49. Cell division increases only the number of cells and cell
expansion but growth is ultimately reflected in tissue
morphology, organ shape and plant architecture
Auxin signaling relates to auxin distribution patterns which is
in turn related to landscape of cell to cell polar auxin
transport canals
Polar transport leads to cell polarity that governs organ
polarity and has immediate bearing on the morphogenetic
patterns
Hence auxin because of its directionally regulated
concentration and signaling poses as the most potent plant
morphogen
Conclusion
49