Abscisic acid and plant adaptation to abiotic stress (Part 2)

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Abscisic acid and plant adaptation to abiotic stress
Abscisic acid and plant adaptation to abiotic stress

Abscisic acid and plant adaptation to abiotic stress

Continuation of the previous part

ABA SIGNAL

Abscisic Acid is an important intracellular signal in plants and plays an important role in various stress responses in plants. Therefore, understanding the signaling mechanism of ABA is important to improve crop yield under stress and is essential as the climate is becoming hotter and hotter. There are three main components involved in ABA signaling: pyralin resistance/pyrabactin resistance (PYL)/regulatory component of the ABA receptor (RCAR), protein phosphatase 2C (PP2C: acts as negative regulators) and (Sucrose) non-fermentative) SNF1 protein kinase 2 (SnRK2: Acts as a positive regulator). In the presence of ABA, the PYR/PYL/RCAR-PP2C complex is formed and leads to the inhibition of PP2C activity, allowing the activation of SnRK2. SnRK2 activation causes proteins downstream to be phosphorylated and to function as transcription factors.

ABA activity under stress

>>> What is abiotic factor? Characteristics and importance

ABA EFFECTIVE RESPONSE AT GENE EXPRESSION LEVEL

Transcriptional Control Regulated by ABA

Transcription factors play a role in the regulation, balance, and coordination of endocrine and developmental signals in plant systems (6). A transcription factor can regulate the expression of multiple target genes through binding to another transcription factor by cis factors in the promoter of the respective target genes. The plant genome contains only about 7% of coding sequences for transcription factors (7).

Drought and salt stress act as a stress signal and lead to ABA accumulation (1). ABA signaling significantly alters gene expression, leading to alterations in transcription, translation, and stability. ABA-dependent gene expression requires association of transcription factors with cis-acting elements in target gene promoters. ABA-activated kinases are responsible for the phosphorylation of ABA-dependent factors (8).

Post-Translation Control in ABA . Conditioning

RNA-binding proteins have important roles in the control of gene expression after transcription, including: mRNA splicing (spicing), mRNA stability, mRNA localization, and translation (9) . RNA-binding proteins play an important role in the response to ABA and often have multiple binding domains capable of inducing motif recognition, such as the K homology domain, zinc finger, cold-shock domain, aspartate-glutamate-alanine -aspartate (DEAD) box, and double-stranded RNA-binding domain (10).

Besides post-translational modification, control by ubiquitin plays an important role in ABA signaling. Ubiquitinization is carried out by enzymes such as ubiquitin-activating enzymes (E1s), ubiquitin conjugating enzymes (E2s), and ubiquitin ligases (E3s). The process of ubiquitinization can affect proteins in a variety of ways: attaching tails to proteins to break down proteins by proteasomes, changing the location of proteins in the cell, promoting or preventing interactions between proteins. Proteins important in ABA signaling are bound to ubiquitin required for proteasome degradation. This process can be induced when ABA is at low concentrations. Proteasome-mediated degradation of ABA receptors allows the release of PP2C, which negatively regulates SnRK2. In other words, when ABA is at high concentrations, this process is inhibited (11).

Epigenetics in Regulation of ABA . Response

Epigenetic variation in the function of a gene is not caused by a change in the DNA nucleotide sequence, but by a chemical alteration of the DNA and its associated proteins. Epigenetic modifications include DNA methylation, histone modification, and microRNA production. Since environmental stressors can induce epigenetic alterations of the genome, leading to an important mechanism mediating gene-environment interactions (12).

Among histone modifications, histone acetylation has been implicated in the regulation of ABA and stress response genes. Histone deacetylation plays an essential role in the activation of ABA-responsive genes for drought adaptation. Conversely, mutations or inhibition of the histone deacetylase gene reduce the expression of ABA and abiotic stress-responsive genes, including salt stress.

Epilogue

The process of climate change is progressing more and more complicatedly and population growth is becoming a great pressure on world agriculture. More and more research is being conducted to improve the yield and increase the resistance of plants. Abscisic acid is one of the important research subjects to improve food varieties today. Besides, many other plant hormones are also being studied. Therefore, we can hope that in the near future, world food security can still be maintained. However, in parallel with the research to create many superior plant varieties, raising people’s awareness to minimize the speed of climate change is also an important aspect.

>>> The difference between abiotic and biotic factors

References:

1. Ng, L. M., Melcher, K., Teh, B. T., and Xu, H. E., “Abscisic acid perception and signaling: structural mechanisms and applications.,” cta Pharmacol., vol. 35, p. 567–584, 2014.

2. Dodd, I. C., Egea, G., and Davies, W. J., “Abscisic acid signaling when soil moisture is heterogeneous: decreased photoperiod sap flow from drying roots limits abscisic acid export to the shoots,” Plant Cell Environ, pp. 31, 1263–1274, 2008.

3. Aswath, C. R., Kim, S. H., Mo, S. Y., and Kim, D. H., “Transgenic plants of creeping bent grass harboring the stress-inducible gene, 9-cis-epoxycarotenoid dioxygenase, are highly tolerant to drought and NaCl Stress,” Plant Growth Regul, pp. 47, 129–139, 2005.

4. Nambara, E., and Marion-Poll, “Abscisic acid biosynthesis and catabolism,” Annu. Rev. Plant Biol, pp. 56, 165–185, 2005.

5. Wilkinson, S., and Davies, W. J., “Drought, ozone, ABA and ethylene: new insights from cell to plant to community,” Plant Cell Environ., pp. 33, 510–525, 2010.

6. Jaradat, M. R., Feurtado, J. A., Huang, D., Lu, Y., and Cutler, A. J., “Multiple roles of the transcription factor AtMYBR1/AtMYB44 in ABA signaling, stress responses, and leaf senescence,” BMC Plant Biol, 2013.

7. Udvardi, M. K., Kakar, K., Wandrey, M., Montanari, O., Murray, J., Andriankaja, A., et al, “Legume transcription factors: global regulators of plant development and response to the environment,” Plant Physiol, pp. 144, 538–549, 2007.

8. Johnson, R. R., Wagner, R. L., Verhey, S. D., and Walker-Simmons, M. K. , “The abscisic acid-responsive kinase PKABA1 interacts with a seed-specific abscisic acid response element-binding factor, TaABF, and phosphorylates TaABF peptide sequences.,” Plant Physiol, p. 837–846, 2002.

9. Glisovic, T., Bachorik, J. L., Yong, J., and Dreyfuss, G. , “NA-binding proteins and post-transcriptional gene regulation. FEBS Lett. 582, 1977–1986. doi: 10.1016/j.febslet.2008.03.004,” FEBS Lett, p. 1977–1986, 2008.

10. Ambrosone, A., Costa, A., Leone, A., and Grillo, S., “Beyond transcription: RNA-binding proteins as emerging regulators of plant response to environmental constraints,” Plant Sci, p. 12–18, 2012.

11. Irigoyen, ML, Iniesto, E., Rodriguez, L., Puga, MI, Yanagawa, Y., Pick, E., “Targeted degradation of abscisic acid receptors is mediated by the ubiquitin ligase substrate adapter DDA1 in Arabidopsis,” 11. Plant Cell, p. 712–728 ,

12. G. J. King, “Crop epigenetics and the molecular hardware of genotype × environment interactions,” Front Plant Sci, p. 968, 2015.

13. Saroj K.Sah, Kambham R.Reddy, Jiaxu Li, “Abscisic Acid and Abiotic Stress Tolerance in Crop Plants,” Plant Sci, 04 May 2016 .

>>> What are biotic and abiotic factors?

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