Abiotic stress responsive microRNome and proteome: how correlated are they?

Environmental stresses, notably drought, soil salinity, extreme temperatures, nutrient deficiency and UV radiation, act both singly and in combination to reduce crop productivity. Plant survival depends on an ability to either tolerate or to avoid stress, so a variety of means have evolved to adjust the growth and development of plants in response to perturbations in their external environment. Plant response to environmental fluctuations requires a programmed change in gene/protein expression which necessitates a tight regulation. The required fine-tuning of gene expression is achieved at multiple levels, of which post-transcriptional regulation represents as one of the main regulatory routes in which microRNAs (miRNAs) play a central role. These short RNA sequences act to suppress their target genes either by inhibiting their translation or by degrading their transcript. The genes encoding miRNAs can themselves be responsive to external stresses. The extent to which stress-induced changes in the plant proteome are influenced by miRNA activity is uncertain, but the implementation of high throughput analytical technologies is beginning to reveal that miRNAs do contribute to the proteomic response to stress. The present review focuses on the impact on the crop plant proteome of stress-induced alterations to miRNome. A particular emphasis is placed on the need to experimentally validate predictions based on bioinformatic data.