Plant buffering against the high-light stress- induced accumulation of CsGA2ox8 transcripts via alter native splici ng to fi n ely tune gibberelli n 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 identi fi ed 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>400μmol-m-2-s-1 PPFD(photosynthetic photon fl ux density),while the CsGA2ox8.2 transcript levels increased rapidly when the light intensity was>200 pmol-m-2-s-1 PPFD.Our fi ndings provide evidence that plants might fi nely tune their GA levels by buffering against the normal transcripts of CsGA2ox8 through AS.