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Article|10 Mar 2021|OPEN
Methyl jasmonate mediates melatonin-induced cold tolerance of grafted watermelon plants
Hao Li1, Yanliang Guo1, Zhixiang Lan1, Kai Xu1, Jingjing Chang1, Golam Jalal Ahammed2, Jianxiang Ma1, Chunhua Wei1 & Xian Zhang1,3,
1State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, 712100 Yangling, Shaanxi, China
2Horticulture, Northwest A&F University, 712100 Yangling, Shaanxi, China 2 College of Horticulture and Plant Protection, Henan University of Science and Technology, 471023 Luoyang, Henan, China
3State Key Laboratory of Vegetable Germplasm Innovation, 300384 Tianjin, China

Horticulture Research 8,
Article number: 57 (2021)
doi: 10.1038/hortres.2021.57
Views: 327

Received: 18 Aug 2020
Revised: 09 Jan 2021
Accepted: 14 Jan 2021
Published online: 10 Mar 2021


Root–shoot communication has a critical role in plant adaptation to environmental stress. Grafting is widely applied to enhance the abiotic stress tolerance of many horticultural crop species; however, the signal transduction mechanism involved in this tolerance remains unknown. Here, we show that pumpkin- or figleaf gourd rootstock-enhanced cold tolerance of watermelon shoots is accompanied by increases in the accumulation of melatonin, methyl jasmonate (MeJA), and hydrogen peroxide (H2O2). Increased melatonin levels in leaves were associated with both increased melatonin in rootstocks and MeJA-induced melatonin biosynthesis in leaves of plants under cold stress. Exogenous melatonin increased the accumulation of MeJA and H2O2 and enhanced cold tolerance, while inhibition of melatonin accumulation attenuated rootstock-induced MeJA and H2O2 accumulation and cold tolerance. MeJA application induced H2O2 accumulation and cold tolerance, but inhibition of JA biosynthesis abolished rootstock- or melatonin-induced H2O2 accumulation and cold tolerance. Additionally, inhibition of H2O2production attenuated MeJA-induced tolerance to cold stress. Taken together, our results suggest that melatonin is involved in grafting-induced cold tolerance by inducing the accumulation of MeJA and H2O2. MeJA subsequently increases melatonin accumulation, forming a self-amplifying feedback loop that leads to increased H2O2accumulation and cold tolerance. This study reveals a novel regulatory mechanism of rootstock-induced cold tolerance.