Overexpression of Caffeic Acid O -Methyltransferase 1 ( COMT1 ) Increases Melatonin Level and Salt Stress Tolerance in T
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Overexpression of Caffeic Acid O‑Methyltransferase 1 (COMT1) Increases Melatonin Level and Salt Stress Tolerance in Tomato Plant Shasha Sun1 · Dan Wen1 · Wanying Yang1 · Qiufeng Meng2 · Qinghua Shi1 · Biao Gong1 Received: 22 June 2019 / Accepted: 28 November 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Melatonin is a natural phytohormone that occurs in most plants. It can regulate not only plant growth and development but also alleviate biotic and abiotic stress in plants. However, no studies have reported on endogenous melatonin increasing tomato tolerance to salt stress. In the present study, we observed that the overexpression of caffeic acid O-methyltransferase 1 (SlCOMT1) increased melatonin levels in tomato plants. We also observed that transgenic plants exhibited higher salt stress tolerance. SlCOMT1 overexpression could maintain the balance of Na+/K+ and decrease ion damage by activating salt overly sensitive (SOS) pathway under salt treatment. In addition, SlCOMT1 overexpression significantly enhanced the antioxidant capability, with higher antioxidant enzyme activity observed, including superoxide dismutase, peroxide and catalase activity, and higher ascorbic acid (AsA) and glutamate (GSH) accumulation levels. SlCOMT1 overexpression also maintained good nutrient homeostasis in the tomato plants. In addition, SlCOMT1 overexpression upregulated some stress-related genes (AREB1, AIM1, MAPK1, WRKY33 and CDPK1), which resulted in the activation of downstream signaling pathways and could be partly responsible for the improvement in salt stress tolerance. Keywords Tomato · Salt stress · SlCOMT1 · Melatonin · Antioxidant capacity · Ion homeostasis
Introduction Tomato is a cash vegetable crop cultivated globally. However, in the course of tomato cultivation, it is often affected negatively by environmental stress, including high and low temperatures, salinity, and drought. Among the above stress factors, the injury caused by salt stress is particularly severe in arid and semi-arid areas, where about 6% of the world’s land areas experience salt stress (Hakeem et al. 2013). Under high-salinity conditions, plants absorb excessive salt ions and ion toxicity and osmotic stress cause damage, which results in the inhibition of plant growth and reduced plant yield (Kong et al. 2017; Moles et al. 2016). * Qinghua Shi [email protected] * Biao Gong [email protected] 1
State Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Taian 271018, People’s Republic of China
Ningbo Academy of Agricultural Sciences, Ningbo, China
2
The accumulation of high concentrations salt ions would also lead to oxidative stress and nutrient disorders (Shalata and Tal 2010; Hussain et al. 2018; Farooq et al. 2018; Gong et al. 2014). Therefore, it is essential to find a strategy for mitigating the damage caused by salt stress. With regard to the ionic aspect of salt stress, the SOS pathway is the key pathway for regulating ion home
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