ARF2-PIF5 interaction controls transcriptional reprogramming in the ABS3-mediated plant senescence pathway

One of the hallmarks of plant senescence is the global transcriptional reprogramming coordinated by a plethora of transcription factors (TFs). However, mechanisms underlying the interactions between different TFs in modulating senescence remain obscure. Previously, we discovered that plant ABS3 subfamily MATE transporter genes regulate senescence and senescence-associated transcriptional changes. In a genetic screen for mutants suppressing the accelerated senescence phenotype of the gain-of-function mutant abs3-1D, AUXIN RESPONSE FACTOR 2 (ARF2) and PHYTOCHROME-INTERACTING FACTOR 5 (PIF5) were identified as key TFs responsible for transcriptional regulation in the ABS3-mediated senescence pathway. ARF2 and PIF5 (as well as PIF4) interact directly and function interdependently to promote senescence, and they share common target genes such as key senescence promoting genes ORESARA 1 (ORE1) and STAY-GREEN 1 (SGR1) in the ABS3-mediated senescence pathway. In addition, we discovered reciprocal regulation between ABS3-subfamily MATEs and the ARF2 and PIF5/4 TFs. Taken together, our findings reveal a regulatory paradigm in which the ARF2-PIF5/4 functional module facilitates the transcriptional reprogramming in the ABS3-mediated senescence pathway.植物衰老的标志性特征之一，是由大量转录因子（transcription factors，TFs）协同调控的全局性转录重编程过程。然而，不同转录因子之间互作调控衰老的具体分子机制仍尚不明确。此前本团队已发现，植物ABS3亚家族MATE转运蛋白基因可调控衰老进程及衰老相关的转录组变化。本团队在针对功能获得性突变体abs3-1D的早衰表型开展抑制突变体的遗传筛选时，鉴定出生长素响应因子2（AUXIN RESPONSE FACTOR 2，ARF2）与光敏色素互作因子5（PHYTOCHROME-INTERACTING FACTOR 5，PIF5）为ABS3介导的衰老通路中负责转录调控的关键转录因子。ARF2与PIF5（以及PIF4）可直接相互作用，并通过相互依赖的方式协同促进衰老；二者在ABS3介导的衰老通路中共享包括关键衰老促进基因ORESARA 1（ORE1）与滞绿基因1（STAY-GREEN 1，SGR1）在内的共同靶基因。此外，本团队还发现ABS3亚家族MATE转运蛋白与ARF2、PIF5/4转录因子之间存在双向调控关系。综上，本研究结果揭示了一套调控范式：ARF2-PIF5/4功能模块可助力ABS3介导的衰老通路中的转录重编程过程。