A translational brake on ABA biosynthesis shapes germination timing and sprouting resistance

Seed germination is a critical developmental switch that depends not only on stored mRNA but also on the selective translation of these transcripts. In this study, Wang et al. explored how translational control of some genes can fine-tune the timing of germination.  Using translation inhibitors and ribosome-defective mutants in Arabidopsis thaliana, the authors showed that active translation is essential for timely germination. Polysome profiling and RNA-seq analyses uncover widespread remodeling of the translational landscape during early germination. One key finding is that ABA2, a gene encoding a central enzyme in the ABA biosynthesis pathway, contains an upstream open reading frame (uORF) in its 5′ untranslated region that suppresses translation of the main coding sequence. Disrupting the ABA2 uORF increases ABA2 protein levels and delays germination. The effect is reversed in aba2 mutants or upon treatment with an ABA biosynthesis inhibitor, confirming a functional link. The study further shows that similar uORF-mediated control exists in rice, where mutations in the OsABA2 uORF reduce preharvest sprouting (PHS). Natural variation in this uORF among rice cultivars correlates with differences in PHS, suggesting it was shaped by domestication and selection. This work identifies a conserved translational control mechanism governing ABA accumulation and germination behavior and introduces uORF variants as potential tools for improving dormancy and sprouting resistance in crops.  (Summary by Muhammad Aamir Khan @MAKNature1998)  PNAS  10.1073/pnas.250215512