Guo Yanliang, Yan Jingyi, Su Zhuangzhuang, Chang Jingjing, Yang Jianqiang, Wei Chunhua, Zhang Yong, Ma Jianxiang, Zhang Xian, Li Hao
State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, China.
Front Plant Sci. 2021 Dec 17;12:785317. doi: 10.3389/fpls.2021.785317. eCollection 2021.
Grafting is widely used to increase plant defense responses to various stresses. Grafting-induced cold tolerance is associated with the increase of the antioxidant potential of plants; however, the underlying mechanisms remain unclear. Here, we found that pumpkin rootstocks promote antioxidant enzyme activities and alleviate cold-induced oxidative damage, accompanied by increased abscisic acid (ABA), melatonin, and methyl jasmonate (MeJA) levels in leaves. Increased ABA accumulation in leaves was attributed partly to the increased ABA levels in rootstocks. ABA induced antioxidant enzymes activities and the accumulation of melatonin and MeJA, while inhibition of ABA synthesis blocked the rootstock-induced antioxidant activity and the accumulation of melatonin and MeJA under cold stress. Melatonin and MeJA application also enhanced ABA accumulation in leaves after cold exposure, whereas inhibition of melatonin or MeJA synthesis attenuated the rootstock-induced increase of ABA. Moreover, melatonin and MeJA application alleviated cold-induced oxidative stress, but inhibition of melatonin or MeJA synthesis lowered the rootstock- or ABA-induced antioxidant potential and tolerance to cold. These findings indicate that ABA plays an important role in the grafting-induced cold tolerance by promoting the accumulation of melatonin and MeJA, which in turn, promote ABA accumulation, forming a positive feedback loop.
嫁接被广泛用于增强植物对各种胁迫的防御反应。嫁接诱导的耐寒性与植物抗氧化能力的增强有关；然而，其潜在机制仍不清楚。在此，我们发现南瓜砧木可促进抗氧化酶活性并减轻冷诱导的氧化损伤，同时叶片中脱落酸（ABA）、褪黑素和茉莉酸甲酯（MeJA）水平升高。叶片中ABA积累的增加部分归因于砧木中ABA水平的升高。ABA诱导抗氧化酶活性以及褪黑素和MeJA的积累，而ABA合成的抑制则阻断了冷胁迫下砧木诱导的抗氧化活性以及褪黑素和MeJA的积累。褪黑素和MeJA的施用也增强了冷暴露后叶片中ABA的积累，而褪黑素或MeJA合成的抑制则减弱了砧木诱导的ABA增加。此外，褪黑素和MeJA的施用减轻了冷诱导的氧化应激，但褪黑素或MeJA合成的抑制降低了砧木或ABA诱导的抗氧化能力和耐寒性。这些发现表明，ABA通过促进褪黑素和MeJA的积累在嫁接诱导的耐寒性中起重要作用，而褪黑素和MeJA反过来又促进ABA积累，形成一个正反馈回路。
