Apomixis is a type of asexual reproduction in which seeds are formed without fertilization. There are two main types - gametophytic apomixis, where an unreduced cell gives rise to an embryo sac, and sporophytic apomixis, where an unreduced cell develops directly into an embryo. Apomixis was first discovered in citrus seeds in 1719 and allows for the production of genetically identical offspring from a single parent. While apomixis has advantages for plant breeding like fixing desirable traits, it is also genetically complex and facultative forms can be affected by environmental conditions.
A game changer in plant breeding
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A game changer in plant breeding
,powerful breeding tool ,genetics ,asexual reproduction ,apomixis technology ,food ,agriculture research ,agriculture ,apomixis
Double fertilization is the process found in angiosperms in which out of the two male gametes released inside the embryo sac, one fuses with the egg cell (syngamy) and another fuse with secondary nucleus (triple fusion).
This P.P.T is about a chapter reproduction in 10th Asexual reproduction Asexual reproduction is a type of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only; it does not involve the fusion of gametes and almost never changes the number of chromosomes. Asexual reproduction is the primary form of reproduction for single-celled organisms such as the archaebacteria, eubacteria, and protists. Many plants and fungi reproduce asexually as well.
Download here: http://www.agrislide.com/fertilization-plants-ppt/
This is a nice presentation on "Fertilization of plants". you can found all of the information of plant fertilization on this presentation.
Apomixis in flowering plants is defined as the asexual formation of a seed from the maternal tissues of the ovule, avoiding the processes of meiosis and fertilization, leading to embryo development.
In flowering plants, the term "apomixis" is commonly used in a restricted sense to mean agamospermy, i.e. clonal reproduction through seeds.
Thus, Apiomixis can be defined as the development of embryo with or without embryosac formation but without fertilization.
Double fertilization is the process found in angiosperms in which out of the two male gametes released inside the embryo sac, one fuses with the egg cell (syngamy) and another fuse with secondary nucleus (triple fusion).
This P.P.T is about a chapter reproduction in 10th Asexual reproduction Asexual reproduction is a type of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only; it does not involve the fusion of gametes and almost never changes the number of chromosomes. Asexual reproduction is the primary form of reproduction for single-celled organisms such as the archaebacteria, eubacteria, and protists. Many plants and fungi reproduce asexually as well.
Download here: http://www.agrislide.com/fertilization-plants-ppt/
This is a nice presentation on "Fertilization of plants". you can found all of the information of plant fertilization on this presentation.
Apomixis in flowering plants is defined as the asexual formation of a seed from the maternal tissues of the ovule, avoiding the processes of meiosis and fertilization, leading to embryo development.
In flowering plants, the term "apomixis" is commonly used in a restricted sense to mean agamospermy, i.e. clonal reproduction through seeds.
Thus, Apiomixis can be defined as the development of embryo with or without embryosac formation but without fertilization.
Polyembryony is the phenomenon of two or more embryos developing from a single fertilized egg. Due to the embryos resulting from the same egg, the embryos are identical to one another, but are genetically diverse from the parents.
This power point is prepared to made easy to understand the method of asexual reproduction in plants for students.It covers both Natural and Artificial Methods of Asexual Reproduction in plants.
This is a quick review which may save your time...
Enjoy... :)
Anther culture:- the in vitro culturing of anthers containing microspores or immature pollen grains on a nutrient medium for the purpose of generating haploid plantlets.
Culturing anthers for the purpose of obtaining Double Haploid is not easy with many field crop species, particularly with the cereals, cotton, and grain legumes.
HYBRIDIZATION & HAPLOID PRODUCTION
Introduction
WIDE HYBRIDIZATION
INTER-SPECIFIC HYBRIDIZATION
Barriers to distant hybridization
Techniques to overcome barriers
Haploids and Doubled Haploids in Plant
Production of haploids and doubled haploids
a) Induction of maternal haploids
Wide hybridization
3. In vitro induction of maternal haploids – gynogenesis
Induction of paternal haploids – Androgenesis
Production of Homozygous Diploid Plants
Application of Haploids in Plant Breeding
Importance and Implications of Anther and Pollen Culture
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.
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.
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 .
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.
2. Apomixis, derived from two Greek word "APO" (away from)
and "mixis" (act of mixing or mingling).
APOMIXS is a type of reproduction in which sexual organs of
related structures take part but seeds are formed without
union of gametes.
The first discovery of this phenomenon is credited to Leuwen
hock as early as 1719 in Citrus seeds.
The genotype of the embryo and resulting plant will be the
same as the seed parent.
This is clonal seed production.
INTRODUCTION
3. Modes of reproduction
Modes of Reproduction
Sexual Asexual
ApomixisVegetative
gametophytic sporophytic
If the unreduced cells give rise to a megagametophyte, then
gametophytic apomixis occurs. If the unreduced cells give
rise directly to an embryo, then sporophytic apomixis occurs.
• Site of origin
• Developmental patternContact Disclaimer
4. APOMIXIS
•Development of embryo without sexual fusion
•Sexual life cycle is “short-circuited”
• Genotypes of developed plants are identical to the
parental plant.
• Discovered by Leuwenhock (1719) in citrus seed
5. Gametophytic Sporophytic
Types of apomixis
unreduced
cells give
rise directly
to an
embryo
unreduced cells give rise to
a megagametophyte
adventitious embryonydiplospory
apospory
the embryo sac
originates from the
megaspore mother cell
either directly by mitosis
and/or after interrupted
meiosis
the embryo sac
originates from nucellar
cells the most common
mechanism of apomixis
in higher plants
characterized by the
presence of multiple
embryo sacs
Parthenogenesis
ApogamyAndrogenesis
The haploid sperm nucleus enters the egg but
does not fuse with the haploid egg nucleus.
Each nucleus divides independently creating a
haploid embryo that contains sectors of male
and female origin.
Semigamy
6. Diplospory – MMC cells give rise to a megagametophyte
Apospory - the embryo sac originates from the any diploid
cell except megaspore mother cell either directly by mitosis
and/or after interrupted meiosis
Androgenesis - the embryo sac originates from generative
nuleus of pollen tube cells the most common mechanism of
apomixis in higher plants characterized by the presence of
multiple embryo sacs
Gametophytic apomixis
If the unfertilized cells give rise to a mega gametophyte
7. Sporophytic apomixis
If the unfertilized cells give rise directly to an embryo
Haploid parthenogenesis : embryo developed from
egg cell
Haploid apogamy (pseudogamy) : embryo
developed from synergids or antipodal cells
Adventitious embrony ( sporophytic budding ) :
embryo directly develop from nucellus or
integuments ( no production of embryosac) e.g.
mango , citrus
11. Types of apomixis based on occurrence :-
1. Non reccurent :- embryo develop from any cell of embryosec
(haploid cell)
Haploid parthenogenesis : embryo developed from egg cell
Haploid apogamy (pseudogamy) : embryo developed from
synergids or antipodal cells
2. Recurrent apomixes : embryosec develop without meiosis from
diploid cell
Diplospory : embryo sec develop from MMC
Apospory : embryo sec develop from any vegetative cell of ovule
,than embyo is developed from diploid egg cell.
3. Adventitious embrony ( sporophytic budding ) : embryo directly
develop from nucellus or integuments ( no production of
embryosac) e.g. mango , citrus
12. The Ideal Apomictic System
1. All the progeny of plants should be apomictic so that
progeny have the same genotype as the maternal parent.
2. The apomictic genotype should preferably be fully male
fertile and self-incompatible, and reproduce via
pseudogamy.
3. In case of diplospory, chromosomes should not pair or
recombine during first meiotic division. which may give
rise to variation among the progeny.
4. Apomixis should be dominant over sexual reproduction.
Usually, apomixis is governed by two or more genes.
5. Expression of apomixis should be little affected by the
environment.
13. Development of Apomictic Lines
Apomictic lines can be developed by the following
three different approaches:
1. Gene Transfer from wild species:
Genes controlling apomixis can be transferred into a
crop species from a related wild species, e.g., from
Tripsacum dactyloides into maize, from Pennisetum
orientate into pearlmillet.
2. Induced Mutations:
This approach aims at developing apomictic forms
in normally sexually reproducing species by
utilising induced or even spontaneous mutations.
14. These efforts have focused primarily on sorghum,
where two mutant lines showing facultative apospory
have been isolated.
3. Isolation of Apomictic Recombinants from
Interspecific Crosses:
Sometimes apomictic recombinants can be recovered
from segregating generations of crosses between two
sexually reproducing species. For example, seed
formation has been reported in the intergeneric hybrids
between T. aestivum and Avena sativa, H. vulgare and
T. aestivitm etc…
15. Rapid production of pure lines
Apomixis is an effective means for rapid production
of pureline.
Maintenance of superior genotypes
Apomixis is useful in maintaining the characteristics
of mother plant from generation to generation.
Conservation of heterosis
In some cases, hybrid vigour may be conserved for
many generation by using recurrent apomixis.
16. Advantages of apomixis in plant breeding
1.Rapid multiplication of genetically uniform individuals can
be achieved without risk of segregation.
2. Heterosis or hybrid vigour can permanently be fixed in
crop plants, thus no problem for recurring seed production
of F 1 hybrids.
3. Efficient exploitation of maternal effect, if present, is
possible from generation to generation.
4. Homozygous inbred lines, as in corn, can be rapidly
developed as they produce sectors of diploid tissues and
occasional fertile gametes and seeds.
17. Obligate apomixis permits fixation of heterosis in the
hybrids. Therefore, farmers can resow the seeds
produced by apomictic hybrids generation after
generation.
The new hybrid variety could be multiplied from few
hybrid seeds in the same manner as purelines. This
greatly simplifies hybrid seed production.
Even such parents that flower at different times may be
crossed in a greenhouse to obtain few hybrid seeds,
which can be used to establish the new hybrid variety.
The nucleus seed of hybrid varieties can be
conveniently maintained as hybrid varieties.
18. • Apomixis is a very complicated phenomenon.
• Estimation of the level of facultative apomixis, is
tedious and time consuming.
• In case of facultative apomicts, the proportion of sexual
progeny is affected by environmental factors like day-
length and temperature.
• In the absence of morphological markers linked with
apomictic development, maintenance of apomictic
stock becomes difficult.
• The genetic basis of apomixis is not clear in most
cases.