Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China.
UWA School of Agriculture and Environment, The University of Western Australia, 35 Stirling Highway, Perth WA, Australia.
J Exp Bot. 2022 Sep 30;73(17):5828-5839. doi: 10.1093/jxb/erac168.
Phytomelatonin is a newly identified plant hormone, and its primary functions in plant growth and development remain relatively poorly appraised. Phytomelatonin is a master regulator of reactive oxygen species (ROS) signaling and acts as a darkness signal in circadian stomatal closure. Plants exhibit at least three interrelated patterns of interaction between phytomelatonin and ROS production. Exogenous melatonin can induce flavonoid biosynthesis, which might be required for maintenance of antioxidant capacity under stress, after harvest, and in leaf senescence conditions. However, several genetic studies have provided direct evidence that phytomelatonin plays a negative role in the biosynthesis of flavonoids under non-stress conditions. Phytomelatonin delays flowering time in both dicot and monocot plants, probably via its receptor PMTR1 and interactions with the gibberellin, strigolactone, and ROS signaling pathways. Furthermore, phytomelatonin signaling also functions in hypocotyl and shoot growth in skotomorphogenesis and ultraviolet B (UV-B) exposure; the G protein α-subunit (Arabidopsis GPA1 and rice RGA1) and constitutive photomorphogenic1 (COP1) are important signal components during this process. Taken together, these findings indicate that phytomelatonin acts as a darkness signal with important regulatory roles in circadian stomatal closure, flavonoid biosynthesis, flowering, and hypocotyl and shoot growth.
植物褪黑素是一种新发现的植物激素，其在植物生长发育中的主要功能仍未得到充分评估。植物褪黑素是活性氧（ROS）信号的主要调节剂，在昼夜节律性气孔关闭中充当黑暗信号。植物表现出至少三种与植物褪黑素和 ROS 产生相互关联的相互作用模式。外源褪黑素可以诱导类黄酮的生物合成，这可能是在胁迫、收获后和叶片衰老条件下维持抗氧化能力所必需的。然而，几项遗传研究提供了直接证据，表明植物褪黑素在非胁迫条件下对类黄酮的生物合成起着负作用。植物褪黑素延迟了双子叶植物和单子叶植物的开花时间，可能是通过其受体 PMTR1 并与赤霉素、独脚金内酯和 ROS 信号通路相互作用来实现的。此外，植物褪黑素信号在 skotomorphogenesis 和紫外线 B（UV-B）暴露中的下胚轴和茎生长中也起作用；G 蛋白α亚基（拟南芥 GPA1 和水稻 RGA1）和组成型光形态建成 1（COP1）是该过程中的重要信号成分。综上所述，这些发现表明，植物褪黑素作为一种黑暗信号，在昼夜节律性气孔关闭、类黄酮生物合成、开花以及下胚轴和茎生长中起着重要的调节作用。
