Alternative splicing: enhancing ability to cope with stress via transcriptome plasticity.

Alternative splicing is a mechanism for the regulation of gene expression that is widespread in higher eukaryotes. Genome-wide approaches, based on comparison of expressed and genomic sequences, on tiling arrays, and on next-generation sequencing, have provided growing knowledge of the extent, distribution and association of alternative splicing with stress-related genes in plants. The functional meaning of alternative splicing in response to stress has been defined for many genes, and in particular for those involved in the regulation of the stress responses, such as protein kinases, transcription factors, splicing regulators and pathogen-resistance genes. The production of proteins with diverse domain rearrangements from the same gene is the main alternative splicing mechanism for pathogen-resistance genes. The plant response to abiotic stress is also characterized by a second mechanism, which consists of the expression of alternative transcripts that are targeted to nonsense-mediated decay. These quantitatively regulate stress-related gene expression. Many alternative splicing events are well conserved among plant species, and also across kingdoms, especially those observed in response to stress, for genes encoding splicing regulators, and other classes of RNA-binding proteins. Nevertheless, non-conserved events indicate that alternative splicing represents an evolutionary strategy that rapidly increases genome plasticity and develops new gene functions, along with other mechanisms such as gene duplication. Finally, the study of the naturally occurring variability of alternative splicing and the identification of genomic regions involved in the regulation of alternative splicing in crops are proposed as strategies for selecting genotypes with superior performance under adverse environmental conditions.