PLANT BIOLOGY Identification of Stress-Regulated MicroRNAs

Small RNAs, either microRNAs (miRNAs) or short-interfering RNAs (siRNAs) are emerging as important regulators of gene expression. MicroRNAs (miRNAs) are short, single-stranded RNAs that inhibit gene expression by posttranscriptionally targeting RNAs for degradation. Short-interfering RNAs (siRNAs) are double-stranded RNAs that also mediate gene silencing. Sunkar and Zhu constructed a library of small RNAs from Arabidopsis seedlings exposed to various stresses, cold, dehydration, high salt, or abscisic acid, in order to identify new small RNAs and gain insight into the roles of small RNAs for mediating abiotic stress responses. Twenty-six new miRNAs were identified and were classified into 15 new families, with two miRNAs falling into previously reported families. In addition, 102 putative siRNAs were identified. Target transcripts regulated by the miRNAs were predicted based on sequence analysis and suggest that more than one miRNA may target the same transcript, that a single miRNA may target multiple transcripts, and that often these transcripts tend to be from members of the same gene family. For example, miR400 is predicted to interact with at least 10 members of the PPR (pentatricopeptide repeat) family. Furthermore, the abundance of several miRNAs was increased or decreased in response to various abiotic stresses, and several of the newly identified miRNAs exhibited tissue or developmental stage-specific expression patterns. These results open the door for further exploration of the role of small RNAs in abiotic stress signaling.

R. Sunkar, J. K. Zhu, Novel and stress-regulated microRNAs and other small RNAs from Arabidopsis. Plant Cell 16, 2001-2019 (2004). [Abstract] [Full Text]