Plant Small RNAs: Biogenesis, Mode of Action and Their Roles in Abiotic Stresses

Small RNAs （sRNAs） are 18-30 nt non-coding regulatory elements found in diverse organisms, which were initially identified as small double-stranded RNAs in Caenorhabditis elegans. With the development of new and improved technologies, sRNAs have also been identified and characterized in plant systems. Among them, micro RNAs （miRNAs） and small interfering RNAs （siRNAs） are found to be very important riboregulators in plants. Various types of sRNAs differ in their mode of biogenesis and in their function of gene regulation, sRNAs are involved in gene regulation at both transcriptional and post-transcriptional levels. They are known to regulate growth and development of plants. Furthermore, sRNAs especially plant miRNAs have been found to be involved in various stress responses, such as oxidative, mineral nutrient deficiency, dehydration, and even mechanical stimulus. Therefore, in the present review, we focus on the current understanding of biogenesis and regulatory mechanisms of plant sRNAs and their responses to various abiotic stresses.

Identification of miR414 and Expression Analysis of Conserved miRNAs from Stevia rebaudiana

MicroRNAs （miRNAs） usually contain 19-24 nucleotides and have been identified as important eukaryotic gene regulators. Applications of various computational approaches have simplified the task by predicting miRNAs from available sequence data sources. In this study, we identified a conserved miR414 from a computational analysis of EST sequence data available from Stevia rebaudiana. In addition, we also identified six conserved miRNAs namely miR169, miR319, miR414, miR164, miR167 and miR398 using stem-loop RT-PCR analysis. Hence, miR414 was commonly identified using both methods. The expression analysis of these miRNAs documented their roles in growth and development of Stevia. Furthermore, the detected miRNAs were found to target genes involved in plant growth, development, metabolism and signal transducfion. This is the first study reporting these conserved miRNAs and their expression in Stevia.

Genome recoding strategies to improve cellular properties: mechanisms and advances

The genetic code,once believed to be universal and immutable,is now known to contain many variations and is not quite universal.The basis for genome recoding strategy is genetic code variation that can be harnessed to improve cellular properties.Thus,genome recoding is a promising strategy for the enhancement of genome flexibility,allowing for novel functions that are not commonly documented in the organism in its natural environment.Here,the basic concept of genetic code and associated mechanisms for the generation of genetic codon variants,including biased codon usage,codon reassignment,and ambiguous decoding,are extensively discussed.Knowledge of the concept of natural genetic code expansion is also detailed.The generation of recoded organisms and associated mechanisms with basic targeting components,including aminoacyl-tRNA synthetase–tRNA pairs,elongation factor EF-Tu and ribosomes,are highlighted for a comprehensive understanding of this concept.The research associated with the generation of diverse recoded organisms is also discussed.The success of genome recoding in diverse multicellular organisms offers a platform for expanding protein chemistry at the biochemical level with non-canonical amino acids,genetically isolating the synthetic organisms from the natural ones,and fighting viruses,including SARS-CoV2,through the creation of attenuated viruses.In conclusion,genome recoding can offer diverse applications for improving cellular properties in the genome-recoded organisms.