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Phytomelatonin is a universal signal molecule that regulates plant growth and stress responses; however, only one receptor that can directly bind with and perceive melatonin signaling has been identified so far, namely AtPMTR1/CAND2 in Arabidopsis. Whether other plants contain a similar receptor and, if so, how it functions is still unknown. In this study, we identified a new phytomelatonin receptor in the monocot maize (Zea mays), and investigated its role in plant responses to osmotic and drought stress. Using homology searching, we identified a plasma membrane-localized protein, Zm00001eb214610/ZmPMTR1, with strong binding activity to melatonin as a potential phytomelatonin receptor in maize. Overexpressing ZmPMTR1 in Arabidopsis Col-0 promoted osmotic stress tolerance, and rescued osmotic stress sensitivity of the Arabidopsis cand2-1 mutant. Furthermore, ZmPMTR1 also largely rescued defects in melatonin-induced stomatal closure in the cand2-1 mutant, thereby reducing water loss rate and increasing tolerance to drought stress. In addition, we identified a maize mutant of ZmPMTR1 , EMS4-06e2fl , with a point-mutation causing premature termination of protein translation, and found that this mutant had lower leaf temperatures, increased rate of water loss, and enhanced drought stress sensitivity. Thus, we present ZmPMTR1 as the first phytomelatonin receptor to be identified and examined in a monocot plant, and our results indicate that it plays an important function in the response of maize to drought stress. [ABSTRACT FROM AUTHOR]

H 2 O 2 affects the expression of genes that are involved in plant responses to diverse environmental stresses; however, the underlying mechanisms remain elusive. Here, we demonstrate that H 2 O 2 enhances plant freezing tolerance through its effect on a protein product of low expression of osmotically responsive genes2 (LOS2). LOS2 is translated into a major product, cytosolic enolase2 (ENO2), and sometimes an alternative product, the transcription repressor c-Myc-binding protein (MBP-1). ENO2, but not MBP-1, promotes cold tolerance by binding the promoter of C-repeat/DRE binding factor1 (CBF1), a central transcription factor in plant cold signaling, thus activating its expression. Overexpression of CBF1 restores freezing sensitivity of a LOS2 loss-of-function mutant. Furthermore, cold-induced H 2 O 2 increases nuclear import and transcriptional binding activity of ENO2 by sulfenylating cysteine 408 and thereby promotes its oligomerization. Collectively, our results illustrate how H 2 O 2 activates plant cold responses by sulfenylating ENO2 and promoting its oligomerization, leading to enhanced nuclear translocation and transcriptional activation of CBF1., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Elsevier Inc. All rights reserved.)