Maize PHYTOMELATONIN RECEPTOR1 functions in plant osmotic and drought stress tolerance

Abstract

Abstract Phytomelatonin is a universal signal molecule that regulates plant growth and stress response. However, only one receptor, AtPMTR1/CAND2 that could directly bind with and perceive melatonin signaling has been identified in dicotyledon plant Arabidopsis so far, whether other plants contain phytomelatonin receptor and how it functions are still unknown. Herein, we identified a new phytomelatonin receptor from monocot maize, and investigated its role in plant osmotic and drought stress response. Using homology searching, maize plasma membrane-localized Zm00001d034063/ZmPMTR1 protein with strong binding activity to melatonin was identified as a potential phytomelatonin receptor in maize. Overexpressing ZmPMTR1 promoted osmotic stress tolerance of the wild-type Arabidopsis plant, and rescued osmotic stress sensitivity of the Arabidopsis cand2-1 mutant. Moreover, ZmPMTR1 largely rescued defect of melatonin-induced stomatal closure in the cand2-1 mutant, thereby reducing water loss rate and increasing drought stress tolerance. Furthermore, we identified a maize mutant of ZmPMTR1, EMS4-06e2fl with a point mutation causing premature termination of protein translation, and found that this maize mutant had lower leaf temperature, increased water loss rate and enhanced drought stress sensitivity. Collectively, our study reveals that ZmPMTR1, as the first identified and analyzed phytomelatonin receptor in monocot plant, functions necessarily in maize plant drought stress tolerance.