Alternative splicing of VRF1 acts as a molecular switch to regulate stress-induced early flowering
Mo‐Xian Chen, Yuan Tian, Fu‐Yuan Zhu, Tao Fan, Hong-Xue Yan, Pengcheng Sun, Min Li, Xuanxuan Hou, Ping Lin, Yu‐Chen Song, Xue Yang, Congming Lu, Jianchang Yang, Anireddy S. N. Reddy, Jianhua Zhang, Ying-Gao Liu
Abstract
Plants frequently evade extreme environmental stress by initiating early flowering, yet the underlying mechanisms remain incompletely understood. Here, through extensive mutant screening, we identify a vegetative growth to reproductive growth transition factor (vrf1) mutant, which exhibits a deficiency in drought escape. Alternative splicing of VRF1 generates four isoforms, of which two encode functional proteins, VRF1-AS1 and VRF1-AS3. The proportions of VRF1-AS1 and VRF1-AS3 are modulated by environmental factors, serving as a molecular switch mediating the transition from tolerance to early flowering, irrespective of their absolute abundance. VRF1-AS1 and VRF1-AS3 competitively bind to MKK1, resulting in MKK1 phosphorylation at different sites, which opens two distinct regulatory pathways. The role of VRF1 is conserved across various conditions, and 66 Arabidopsis ecotypes suggest its central function in stress avoidance through premature flowering. In summary, our findings show that plants respond precisely and effectively to dynamic environmental changes by modulating their isoform ratios.