Mechanism of high ambient temperature-induced leaf senescence in plants

Abstract

Heat stress is one of the most critical abiotic stress in plants. Heat stress accelerates leaf senescence in diverse plant species. However, the exact regulation mechanism of high ambient temperature-induced senescence is largely unknown. Here, we examined that phytochrome-interacting factor PIF4 and PIF5 (PIF4/5) are required for high ambient temperature-induced senescence in Arabidopsis thaliana. After prolonged dark incubation at $28^{\circ}C$, wild type seedlings turned to yellow, while $pif4/5$ double mutant showed green cotyledons. The results indicated that PIF4/5 promotes the high ambient temperature-induced senescence. We investigated whether high ambient temperature-induced senescence is regulated by phyB. High ambient temperature promotes PIF4 protein accumulation both phyB-dependently and phyB-independently. $PIF4$ mRNA was up-regulated at high ambient temperature via ELF3 but not phyB. We concluded that high ambient temperature accelerates the leaf senescence both phyB-dependently and phyB-independently. PIF4/5 accelerates senescence by increasing $ORE1$ mRNA together with ABA and ethylene signaling at high ambient temperature. Our results suggested that PIF4 and PIF5 integrate not only light signaling but also temperature signaling in the regulation of leaf senescence.