Role of sRNAs in abiotic stress tolerance

Abstract

Any external factors either biotic or abiotic that significantly reduced the plants’ ability to convert light energy into biomass are studied under a broad category termed stresses that negatively influence the metabolic activities of plants. Along with biotic and abiotic stresses, overgrowing population also caused a lot of pressure on agricultural fields to fulfill the food demand, but the crops productivity was not increased in such manner as population increased. In natural environment, primary producers, that is, plants face a number of adverse environmental conditions such as high salinity, drought, cold, and heat that limits the biomass production and yield of staple food crops; hence, it is a global concern to fulfill the food demand. Various anthropogenic activities contribute to the abiotic stress that changes the climate of environment that causes threat to food security. These adverse environmental changes hamper the various physiological and metabolic factors that results in death of plants. A physiological alteration under abiotic stresses includes growth inhibition associated with photosynthetic pigment loss, decreased whole-cell oxygen evolution (photosynthesis), and significant increase in oxygen consumption. Plants stimulate various adoptive changes in response to abiotic stresses at physiological, cellular, and molecular level or through genetic regulation or reprogramming the expression of gene. Physiological adaptation includes change in protein modification at transcriptional level as well as at posttranslational level that leads the change in particular phenotype that significantly avoids the stressful conditions. One such approach is through the modification in gene expression and also through the activity of sRNAs, which switches on protective mechanisms, that is, the genes that involve in defense systems are upregulated and gens that involve in toxicity are downregulated. Role of proteomics as stress-tolerance mechanism is well known, whereas the role of sRNA as stress regulators is an emerging molecular tool. Further, due to the development of modern molecular techniques, molecular mechanisms in plants give much more attention to identify the stress-responsive proteins and their regulatory gene networks under posttranslational level. In this line, small noncoding RNAs (sRNAs) are considered posttranscriptional regulatory factor in gene regulation under adverse environmental factors and involved in plant development. In molecular world, RNAs are basically categorized into two into transfer RNA and ribosomal RNA, and the only difference in sRNAs from other forms of RNAs is relatively small size of genome (20-30nt) as well as having capacity to make complex with argonaute (AGO) family proteins considered key components of RISC (RNA-induced silencing complex). Among various types of sRNA, two are major, that is, microRNAs and small interfering RNAs that actively mediate the gene regulation, splicing, DNA methylation, chromatin, protein, and nucleotide modification and sRNA-mediated gene silencing termed RNA interference (RNAi). RNAi significantly inhibits the process of transcription or translation by sequence-specific gene regulation initiated by dsRNA and frequently presents in plants as well as in animals, fungi, and ciliates. The present time is totally dependent on crop improvement techniques under adverse environmental conditions by the use of various molecular approaches and among them RNAi is considered an important tool of genetic engineering and functional genomics. In this chapter, we briefly describe the biogenesis of sRNA and their pivotal role against abiotic stress tolerance. © 2020 Elsevier Inc. All rights reserved.