Plant buffering against the high-light stress-induced accumulation of CsGA2ox8 transcripts via alternative splicing to finely tune gibberellin levels and maintain hypocotyl elongation

In plants, alternative splicing (AS) is markedly induced in response to environmental stresses, but it is unclear why plants generate multiple transcripts under stress conditions. In this study, RNA-seq was performed to identify AS events in cucumber seedlings grown under different light intensities. We identified a novel transcript of the gibberellin (GA)-deactivating enzyme Gibberellin 2-beta-dioxygenase 8 (CsGA2ox8). Compared with canonical CsGA2ox8.1, the CsGA2ox8.2 isoform presented intron retention between the second and third exons. Functional analysis proved that the transcript of CsGA2ox8.1 but not CsGA2ox8.2 played a role in the deactivation of bioactive GAs. Moreover, expression analysis demonstrated that both transcripts were upregulated by increased light intensity, but the expression level of CsGA2ox8.1 increased slowly when the light intensity was >400 mu mol.m(-2).s(-1) PPFD (photosynthetic photon flux density), while the CsGA2ox8.2 transcript levels increased rapidly when the light intensity was >200 mu mol.m(-2).s(-1) PPFD. Our findings provide evidence that plants might finely tune their GA levels by buffering against the normal transcripts of CsGA2ox8 through AS.

Automated summary

In response to environmental stresses, plants induce alternative splicing to generate multiple transcripts, allowing for fine-tuning of gibberellin levels. The study identified a novel transcript of the gibberellin-deactivating enzyme CsGA2ox8 and demonstrated that different isoforms play distinct roles in deactivating bioactive GAs. Expression analysis showed that under different light intensities, the transcripts of CsGA2ox8 were upregulated at varying rates, suggesting a regulatory mechanism through alternative splicing in plants.