Dynamics of mRNA fate during light stress and recovery: from transcription to stability and translation

The stability of mRNA is an important determinant of its abundance and, consequently, protein production. There has been extensive research on the pathways governing mRNA stability and translation, however, it is unclear the extent to which these processes are modulated by environmental conditions. We previously modelled rapid recovery gene down-regulation (RRGD) following light stress in Arabidopsis thaliana (Arabidopsis) using mathematical calculations to account for transcription in order to predict half-lives and led to the hypothesis of recovery-specific transcript destabilisation. Here, we test this hypothesis by quantifying changes in transcription, mRNA stability, and translation in leaves of mature Arabidopsis undergoing light stress and recovery and investigate processes regulating transcript abundance and fate. Compared to juvenile plants from prior work, here we find that stability is altered for a range of transcripts that encode proteins involved in post-transcriptional processes in mature leaves. We also observe transcript destabilisation during light stress, followed by re-stabilisation upon recovery. Alongside this, we observe fast transcriptional shut-off in recovery that, when paired with transcript destabilisation, promotes rapid down-regulation of stress-induced genes. Translation was dynamic over the course of light stress and recovery, with substantial transcript-specific increases in polysome loading observed during late stress independently of total mRNA abundance. Taken together, we provide evidence for the combinatorial regulation of transcription, mRNA stability, and translation that occurs during light stress and recovery.