Kyonoshin Maruyama, Takuma Ishizaki, Shingo Goto, Miho Kishimoto, Kyouko Yoshiwara, Masaki Endo, Miyako Kusano, Makoto Kobayashi, Mikiko Kojima, Yumiko Takebayashi, Hitoshi Sakakibara, Tetsuya Sakurai, Shingo Sakamoto, Nobutaka Mitsuda
Drought coordinates hormonal, transcriptional, and metabolic reprogramming, but how abscisic acid (ABA) and 1-aminocyclopropane-1-carboxylic acid (ACC) jointly shape cereal dehydration responses remains unclear. We integrated hormone profiling, transcriptome and promoter analyses, synthetic promoter assays, and metabolite profiling in rice. ABA and ACC contents increased markedly in rice shoots under moderate soil water deficit. Combined ABA + ACC treatment showed larger absolute overlaps with dehydration-responsive genes than either ABA or ACC treatment alone in shoots; in roots, this pattern was observed for induced but not repressed genes. Promoters of dehydration- and ABA-inducible genes were enriched in ACGT-core motifs, including a CGTACG core preferentially embedded in ACGTACGT, designated the eXtended ACGT box (Xbox). Multimerised Xbox conferred transcriptional induction under soil water deficit and in response to ABA. OsICL was induced under soil water deficit and by ABA or ACC; in shoots, combined ABA + ACC treatment produced the highest mean transcript accumulation. OsICL overexpression and knockout lines showed altered organic-acid, sugar, and amino-acid profiles, particularly under soil water deficit, but several metabolites changed in the same direction in both line classes. These findings support an ABA-centred, ACC-modulated model of dehydration-responsive transcription and associate OsICL regulation with broader, condition-dependent changes in primary metabolism.