Alternative splicing in plant immunity

Abstract

Alternative splicing (AS) occurs widely in plants and can provide the main source of transcriptome and proteome diversity in an organism. AS functions in a range of physiological processes, including plant disease resistance, but its biological roles and functional mechanisms remain poorly understood. Many plant disease resistance (R) genes undergo AS, and several R genes require alternatively spliced transcripts to produce R proteins that can specifically recognize pathogen invasion. In the finely-tuned process of R protein activation, the truncated isoforms generated by AS may participate in plant disease resistance either by suppressing the negative regulation of initiation of immunity, or by directly engaging in effector-triggered signaling. Although emerging research has shown the functional significance of AS in plant biotic stress responses, many aspects of this topic remain to be understood. Several interesting issues surrounding the AS of R genes, especially regarding its functional roles and regulation, will require innovative techniques and additional research to unravel.

Figure 1

Schematic diagramof gene structure and transcript isoforms for the TIR-NBS-LRR genes Arabidopsis RPS4 (A); tobacco N (B); M. truncatula RCT1 (C); and flax L6 (D). Exons are shown as boxes. The cryptic introns are indicated by vertically hatched boxes in the exons, and horizontally hatched boxes for cryptic exons in introns. The spliced and retained introns are shown as angled and straight lines, respectively. RT, regular transcript encoding the full-length protein product; AT, alternative transcript encoding an aberrant protein product; E, exon; I, intron.