イネにおける温度感受性種子発芽を調整するOsFTIP9とOSH1間の正のフィードバックループ

Seed germination, critical for seedling establishment and subsequent development, is regulated by endogenous hormones and external environment stimuli. However, the molecular mechanisms governing temperature-sensitive seed germination remain largely unclear. In this study, we identify a temperature-sensitive regulatory module controlling rice seed germination, wherein FT-interacting protein 9 (OsFTIP9) promotes seed germination under optimal temperature by interacting with Oryza sativa HOMEOBOX 1 (OSH1) and sequestering it in the cytosol, thus limiting its nuclear translocation. Within the nucleus, OSH1 directly activates the expression of ABA biosynthetic genes, 9-cis-epoxycarotenoid dioxygenase 3 (OsNCED3) and OsNCED5, by facilitating chromatin loop formation. Crucially, reduced nuclear OSH1 activates OsFTIP9 expression, establishing a positive feedback loop that amplifies OsFTIP9 accumulation and promotes seed germination. Under optimal temperatures, osftip9 and OSH1 RNAi mutants exhibit altered germination compared with the wild type, whereas- these differences are abolished under low temperature. Intriguingly, low temperature impairs OsFTIP9-mediated cytosolic retention of OSH1, promoting its nuclear accumulation, ABA biosynthesis and ABA-dependent seed dormancy. Collectively, our study identifies the OsFTIP9-OSH1 module as a temperature-sensitive molecular switch that, integrates environmental cues to precisely control ABA-regulated seed dormancy and germination through reciprocal regulation and spatial sequestration, elucidating a key mechanism underlying temperature-sensitive seed germination and providing potential targets for improving germination-stage cold tolerance in rice.