Functional analysis of the role(s) of microRNAs in the control of plant architecture and fruit development

Abstract

Small regulatory RNAs or sRNAs (19-25 nt) regulate transcriptionally and posttranscriptionally gene expression in plants, modulating their transcriptome and proteome. Among these small RNAs, microRNAs (miRNAs) arise as key regulators of development, as observed phenotypically and molecularly in transgenic and mutant plants harboring genetic modifications in the miRNA pathways. MicroRNAs are generated from long single-strand RNA molecules (pri-miRNAs) that are processed by different enzymes to produce the mature miRNA. In plants, mature miRNA preferentially "guides" the cleavage of their mRNA targets. Transgenic as well as mutant plants ectopically expressing specific microRNAs and/or target genes show distinct and important modifications in plant architecture and development of reproductive organs. For instance, transgenic tomato (Solanum lycopersicum L.) cv. Micro-Tom (MT) plants overexpressing the microRNA156, generated by our research group display more axillary branches, higher biomass as well as modified flowers and navy-like fruits. Although it has been shown that this microRNA affects plant architecture, a genome-wide analysis of genetic/metabolic pathways modified by and that may interact with miR156-regulated pathway is lacking, mainly in economically important crops such as tomato. The combination of using available mutants and transgenic plants overexpressing microRNAs and/or miRNA-resistant versions of their gene targets, as well as the use of RNA next-generation sequencing techniques, allows detailed analyses of possible genetic/metabolic pathways that have been modified by regulatory RNAs and impact plant development. The identification and characterization of such pathways would contribute not only for our better knowledge about plant development, but also have potential applications in crop breeding. (AU)