The auxin response factor TaARF15-A1 negatively regulates senescence in common wheat (Triticum aestivum L.)

An auxin response factor delays leaf senescence via protein-protein interaction and competitively binding to promoter regions of a transcription factor in common wheat. Auxin plays an important role in regulating leaf senescence. Auxin response factors (ARFs) are crucial components of the auxin signaling pathway; however, their roles in leaf senescence in cereal crops are unknown. In this study, we identified TaARF15-A1 as a negative regulator of senescence in wheat (Triticum aestivum L.) by analyzing TaARF15-A1 overexpression (OE) and RNA interference lines and CRISPR/Cas9-based arf15 mutants. OE of TaARF15-A1 delayed senescence, whereas knockdown lines and knockout mutants showed accelerated leaf senescence and grain ripening. RNA-seq analysis revealed that TaARF15-A1 delays leaf senescence by negatively regulating senescence-promoting processes and positively modulating senescence-delaying genes including senescence-associated phytohormone biosynthesis and metabolism genes as well as transcription factors (TFs). We also demonstrated that TaARF15-A1 physically interacts with TaMYC2, a core jasmonic acid (JA) signaling TF that positively modulates wheat senescence. Furthermore, TaARF15-A1 suppressed the expression of TaNAM-1 (TaNAM-A1 and TaNAM-D1) via protein-protein interaction and competition with TaMYC2 for binding to its promoter to regulate senescence. Finally, we identified two haplotypes of TaARF15-A1 in global wheat collections. Association analysis revealed that TaARF15-A1-HapI has undergone strong selection during wheat breeding in China, likely owing to its earlier maturity. Thus, we identify TaARF15-A1 as a negative regulator of senescence in common wheat and present another perspective on the crosstalk between auxin and JA signaling pathways in regulating plant senescence.