Identified of a novel cis-element regulating the alternative splicing of LcDREB2

Alternative splicing (AS) is an important gene regulation mechanism in plants. Despite the widespread use of AS in plant gene expression regulation, the identification of the cis-elements involved in the AS mechanism is rarely reported in plants. To explore the regulation mechanism of the AS of LcDREB2, a DREB2 ortholog from Sheepgrass (Leymus chinensis), the genomic sequences of LcDREB2 and its homologs in Poaceae were aligned, and six mutations were introduced in the conserved sequence of LcDREB2. By analyzing the distinct transcript patterns of the LcDREB2 mutants in transgenic Oryza sativa, a novel cis-element that affected the AS of LcDREB2 was identified as Exonic Splicing Enhancer 1 (ESE1). In addition, five serine-arginine rich (SR) proteins were confirmed to interact with ESE1 by electrophoretic mobility shift assay (EMSA). To further explore the expression regulation mechanism of the DREB subfamily, phylogenetic analysis of DREB2 paralogous genes was performed. The results strongly supported the hypothesis that AS is conserved in Poaceae plants and that it is an evolutionary strategy for the regulation of the functional expression of genes. The findings and methods of our study will promote a substantial step forward in understanding of the plant AS regulation mechanism.