Role of small RNAs in plant

1. 1

2. seminar
Role of miRNAs in Responses to abiotic Stress
in plants
Supervisor
Dr. Alemzadeh
Provisioner
Nazila gharibi
Spring 1400
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3. ➢ Introduction
➢ What are miRNA’s?
➢ MicroRNA (miRNA) biogenesis
➢ Abiotic stress and miRNAs
➢ Stress - miRNA networks
➢ miRNAs Regulating Oxidative Stress
➢ MicroRNAs Expression Under Salt Stress
➢ Role of miRNAs during Nutrient Deprivation
➢ miRNA-based strategies for crop
improvement
➢ Database
➢ Conclusion and Future prospects
Over view
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4. • Plant growth and productivity is adversely affected by frequent exposure to a plethora
of stress conditions
• All stress factors are a menace for plants and prevent them from reaching their full
genetic potential and limit the crop productivity thereby threaten the sustainability of
agricultural industry.
• Various genes are up-regulated and down-regulated, to mitigate the effect of stress
and lead to adjustment of the cellular milieu and plant tolerance.
• Recently, microRNAs (miRNAs) have emerged as powerful molecules, which
potentially serve as expression markers during stress conditions.
Introduction
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5. Stress
The most practical definition of
stress is “an adverse force or a
condition, which inhibits the
normal functioning or well being
of a biological system such as
plants” (Jones et al,1989).
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6. Small RNA (sRNA)?
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7. Differences and similarities between sRNAs and mRNAs
TGS & PTGS 7

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9. Production of cottonseed with RNAi
❖ Gossypol and delta-cadinene synthase (dCS) enzyme
❖ dCS was targeted in the seed through RNAi to interfere with gossypol biosynthesis.
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11. What are miRNA’s?
• miRNAs are about 20–22(nt), single-stranded RNAs processed by
the Dicer-like (DCl) family of enzymes in plants.
• A capitalized "miR-" refers to the mature form of the miRNA, while
the uncapitalized "mir-" refers to the pre-miRNA and the pri-miRNA.
• Genes encoding miRNAs in plants are annotated as MIR genes.
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12. Victor Ambros & Rosalind
Victor Ambros and Gary Ruvkun won 2015’s Breakthrough Prize in
Life Sciences.
How miRNA was Discovered?
Rhonda Feinbaum
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13. The first miRNA of plant origin was identified in 2002 in Arabidopsis
thaliana (Llave et al. 2002; Park et al. 2002; Reinhart et al. 2002).
Discovery of a second microRNA: Let-7
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14. MicroRNA (miRNA) biogenesis and mode of action
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15. MicroRNA (miRNA) biogenesis in Plant
• Primary miRNA
(pri-miRNA)
• Precursor miRNA
(pre-miRNA)
• miRNA/miRNA*
• Mature miRNA
• Dicer like enzyme
(DCL1)
• HYPONASTIC
LEAVES 1 (HYL 1)
• HUA ENHANCER
(HEN 1)
• HASTY (HST)
(Exportin-5
Homologue)
• Argonaute protein
(AGO)
• RNA induced
silencing complex
(RISC)
15
plant animal

16. • (A) Messenger RNA cleavage. Black arrowhead indicates site of cleavage.
• (B) Translational repression (H3K4me3)
• (C) Transcriptional silencing, thought to be specified by siRNAs.
The Actions of Small Silencing RNAs
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17. Nearly half of the targets of conserved
miRNAs are transcription factors.
Some miRNAs are highly conserved
and important gene regulators
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18. Representative miR164 stem-loops from
Arabidopsis, Oryza, and Populus.
All known miRNA families that are conserved
between more than one plant species.
Jones-Rhoades
et
al.,
2006
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19. The first strategy is to make transgenic plants that overexpress a miRNA, typically
under control of the strong 35S promoter.
Reverse genetics
random induction of DNA deletions
subsequent selection for deletions
RNA interference
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20. The second strategy is to make transgenic plants that express a miRNA-resistant target.
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21. Plants respond to these adverse conditions in various forms, broadly categorized as:
• Physiological responses-involve various proteins, transcription factors and
metabolites, etc.,.
• Genetic responses-involve epigenetic changes, including RNA-directed DNA
methylation, histone and DNA modifications.
• It has been reported that
regulation of stress-related genes
and miRNAs are correlated
(Sunkar and Zhu 2004). the
identification of stress-associated
genes as miRNA targets provided
clues about the role of miRNAs in
stress responses.
Abiotic stress and miRNAs
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22. Stress–miRNA networks responsive miRNAs in Arabidopsis
(
Source:
Khraiwesh
B,
Zhu
KJ,
Zhu
J.
2012.
Biochimica
et
Biophysica
Acta
1819:
137–148.)
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24. Table
1.
List
of
studies
on
the
functional
role
of
different
miRNA/miRNA
families
in
the
regulation
of
abiotic
and
biotic
tresses
in
major
crop
species
(December
2020).
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26. Distribution of miRNAs and plant species involved in 35 different abiotic stresses.
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27. ▪ Abiotic stress causes generation of ROS and their accumulation to toxic concentrations.
• ROS cause oxidative damage to membrane lipids, proteins and nucleic acids.
• Plants have developed sophisticated ROS detoxification system.
• In Arabidopsis, abiotic stress-inducible Cu-Zn SOD genes, namely CSD1 (encodes cytosolic
SOD) and CSD2 (encodes chloroplastic SOD), have been identified as targets of abiotic
stress down-regulated miR398.
miRNAs Regulating Oxidative Stress
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28. Source: Bej S and Basak J. 2014. American Journal of Plant Sciences. 5: 748-759.
Role of miR398 in Oxidative stress
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29. Gao et al. 2016. Nature. 6: 19736
MicroRNAs Expression Under Salt Stress
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30. • miR399, miR395 and miR398 are induced in response to
phosphate, sulfate and Cu2+ deprived conditions, respectively.
Role of miRNAs during Nutrient Depriviation
S miRNAs regulating Sulfate Depriviation
P miRNAs regulating Phosphate Starvation
Cu
miRNAs regulating Copper Starvation
• miR395 has two potential targets:
• The first target is ATP sulfurylase (APS1, APS3 and APS4) enzyme that
catalyzes the first step of the sulfur assimilation pathway.
• The second target of miR395 is AST68, an Arabidopsis sulfate
• miR399 has two target genes belonging to different families: a phosphate
transporter and a putative ubiquitin conjugating enzyme (UBS24) possibly
involved in protein degradation
• Copper starvation induces miR398 expression, which further suppresses the
translation of CSD1 and CSD2 mRNA into CuSOD proteins
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31. Source: Bej S and Basak J. 2014. American Journal of Plant Sciences. 5: 748-759.
• PHO 2
• UBS 24
Don’t
phosphate
uptake
miRNAs and Phosphate homeostasis
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32. Overview of miRNA-based strategies for crop improvement
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33. Overview of miRNA-based strategies for crop improvement
Short Tandem Target MIMIC (STTM)
miRNA recognition elements (MRE)
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35. ➢ In addition to the fundamental role of gene silencing, plant miRNAs play diverse
roles in almost all biological (molecular) networks.
➢ The potential of plant miRNAs in regulating stress-responsive genes makes them
a suitable candidate for developing stress tolerant crop varieties.
➢ A deeper understanding of the molecular mechanism regulated by miRNA in the
complex molecular networking systems would enable agricultural scientists to
manipulate specific agronomical traits in crops.
➢ However, the regulation of multiple genes and networks by single miRNA in
plants makes the selection of candidate miRNA to target specific agronomically
important trait challenging for the scientists.
➢ For such traits, efficient tools are required to decipher pri-miRNA-mediated
regulatory networks.
Conclusion and Future prospects
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