This is a detailed presentation on Morphology, anatomy and reproduction of Marchantia spp. with high quality pics and eye capturing transitions and animations
This is a detailed presentation on Morphology, anatomy and reproduction of Marchantia spp. with high quality pics and eye capturing transitions and animations
Bryophytes are small, non-vascular plants, such as mosses, liverworts and hornworts. They play a vital role in regulating ecosystems because they provide an important buffer system for other plants, which live alongside and benefit from the water and nutrients that bryophytes collect.
Bryophytes are small, non-vascular plants, such as mosses, liverworts and hornworts. They play a vital role in regulating ecosystems because they provide an important buffer system for other plants, which live alongside and benefit from the water and nutrients that bryophytes collect.
the presentation is about morphology of selaginella. this plant belongs to pteridophytes. in this presentation you will study about vegetative part of the plant like roots, stem, leaves, rhizophore and ligule etc.
The topic of discussion is Pteridophytes, their general characteristics, sexual reproduction and Life cycle has been discussed along with the four different divisions that are present in Pteridophytes
• Marsilea hirsuta & Marsilea quadrifolia are two most common Indian species, usually found growing in marshy places, wet soil or near muddy margins of ponds.
• The species are hydrophytic or amphibious i.e., they grow rooted in mud or marshes and shallow pools or are completely submerged or partially or entirely out of water in wet habitats.
Ginkgo is known as a Living Fossil.Anatomy of Ginkgo clearly shows primary and secondary structures. sex in Ginkgo is determined by sex chromosomes (XY in male and XX in female). Reproductive bodies of Ginkgo are most primitive among living seed plants except some Cycadales. Ginkgos are dioecious, with separate sexes, some trees being female and others being male. Male plants produce small pollen cones with sporophylls, each bearing two microsporangia spirally arranged around a central axis. Female plants do not produce cones. Two ovules are formed at the end of a stalk, and after pollination, one or both develop into seeds. The fertilization of ginkgo seeds occurs via motile sperm, as in cycads, ferns, mosses and algae.
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 .
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
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.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
5. Root
The root of young sporophyte is
of primary root while others are
adventitious.
The adventitious roots are at the tips
of rhizophore.
6. Stem
Stem is green, dorsiventral and prostrate
with short erect branches.
The branches are arranged
dichotomously.
The shoot apex consists of a single apical
cell in most cases.
7. Rhizophore
In some species , leafless and colorless branches arise
from the prostrate stem near point of branching.
These grow downwards and have group of
adventitious roots
They are called as rhizophores
Some scientist consider them branches and some
consider them as roots and still other consider it as
an organ for protection or other function.
But recently they are known as adventitious roots
that have dichotomous branches at tip.
8. Leaves
Microphylls are present. ( leaves
are small and single veined. They
are of 2 types
1. Isophyllous
2. Anisophyllous.
The anisophyllous leaves are in pairs.
They may be
Small: these are inserted on the
dorsal side of stem
Larger: these leaves are inserted
on the ventral side of stem
9. Ligules
Ligule: there is small outgrowth on adaxial side (
upper side) of the leaf near base. It is vestigial
organ and provide water .
11. Stem anatomy
Epidermis : thick epidermis , thin walled,
rectangular cells, covered with cuticle
cortex : many layered , outer 2-4 are thick
walled called as hypodermis
endodermis :the cortex and central tissue
is connected by radially elongated cells
called trabeculae
12. Leaf anatomy
The upper and lower epidermis are present
They are one celled thick and contain chloroplast
Stomata are present on upper and lower epidermis
(
but majority have in lower side)
Below the epidermis there is mesophyll tissue having
thin walled parenchyma cells, these contain chloroplast
and have small and large air spaces
Vascular tissue is present in center
14. Strobilus
The strobilus is the spore-bearing structure,
with both male and female spores being
produced.
The male spores are contained within
the sac at lower right.
The much larger female spores are in the sac at
lower left.
16. Structure of sporangia
Microsporangia : they are small, stalked, oval
and varying in shapes,
Mega sporangia : they are stalked and 4
lobes, larger in size and present at base of
strobilus , spores are of larger size.
1. Both consist of 2 layered sporangial wall
surrounding the tapetum and sporogenous
tissue.
2. Tapetum is developed from innermost layer
of sporangial wall.
3. Both differ in their size, location, and number
of spores.
17. Sexual reproduction ( gametophyte )
Microspores and macrospores develop into male
and female gametophyte
Germination is precocoious ( within the walls of
sporangia)
Male gametophyte is released at 13 celled stage
while female gametophyte comes at various
stages , depending upon the species.
18. Microspore
The microspores are very minute in size.
The spore wall is two- layered. The outer exine
is very thick .
The inner inline (endospore) is thin and delicate.
The spore consists of reserve food material in
the form of oil globules and nitrogenous material.
19. Megaspores
The megaspores are much bigger in size
than the microspores .
The wall of the megaspore is very thick and
consists of a exine, a middle mesospore and
a thin intine.
20. Life cycle
Life cycle in selaginella is
characterized by alternation
of generation.
Both spore producing and
gamete producing generation
are independent.
21. References
Vashistha, P.C., Sinha, A.K., Kumar, A.
(2010). Pteridophyta. S. Chand. Delhi,
India.
Images- www.shutterstock.com
