Dynamic hormone flux and gene-metabolite integration influence drought tolerance and tiller plasticity under drought...

Drought during the seedling and jointing stages reduced the survival of primary and secondary tillers. The jointing drought highly determines tiller plasticity by inducing the degradation of both early-produced primary and late-formed secondary tillers, especially secondary tillers, determining tiller plasticity in both cultivars with variation among them, while seedling drought mainly inhibited tiller initiation, having less influence on plasticity. RM523 showed higher primary and secondary tiller numbers, reflecting its strong tillering potential under drought. Tiller number increases with CTK and IAA, and decreases with ABA and GA, while sugar content showed the opposite relationships. The increased hormone flux ratio and sugar content at jointing drought indicate increased tiller mortality. Biological mechansims such as hormone and MAPK signaling transduction, carbon metabolism, nucleotide, and carotenoid biosynthesis, with high enrichment of DEGs that vary with cultivars and growth stages. During the jointing stage, more DEGs were downregulated in RM523 compared to YM20, indicating that carbohydrate metabolism regulates tillering. More transcript-metabolite integration was involved in XTHs/Xyloglucan endotransglucosylase, adenylate isopentenyltransferase, gibberellin 2-beta-dioxygenase, auxin-responsive protein SAUR32, ABA 8'-hydroxylase, and ABA-inducible protein PHVA1, which influence tiller formation at both stages. The ABA-responsive and cell-modifying XTH genes promote tiller mortality during the jointing stage. This study explored the novel cytokinesis protein sepA, two unnamed transcripts, and metabolites like trigonelline, ectoine, piperlongumine, folates, biotin, dethiobiotin, apiole, and p-coumaric acid, which emerged as novel candidates for drought tolerance and tillering; no evidence exists in wheat that needs further functional study to elucidate their role in enhancing drought resilience.