Chinese Bulletin of Botany ›› 2023, Vol. 58 ›› Issue (5): 720-732.DOI: 10.11983/CBB22202

• EXPERIMENTAL COMMUNICATIONS • Previous Articles     Next Articles

Regulatory Mechanism of Melatonin on Tomato Seed Germination Under Cd2+ Stress

Cai Shuyu(), Liu Jianxin, Wang Guofu, Wu Liyuan, Song Jiangping   

  1. Shaoxing University Yuanpei College, Shaoxing 312000, China
  • Received:2022-08-26 Accepted:2022-12-01 Online:2023-09-01 Published:2023-09-21
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Abstract: Soil cadmium (Cd) pollution seriously restricts the yield and quality of facility vegetables. Melatonin (MT) can enhance the resistance to various stresses in plants. However, the downstream signals, which regulated by MT during tomato seed germination under Cd2+ stress remains unclear. The effects of Cd2+ stress and exogenous MT on seed germination were investigated using tomato (Solanum lycopersicum) wild-type Alisa Craig seeds. The results showed that the germination of tomato seeds and seedling growth were significantly inhibited by Cd2+ treatment with more than 0.5 mmol·L-1. Exogenous MT (0.15 mmol·L-1) reduced the content of Cd2+ in the underground and above-ground tissues of seedlings, effectively alleviating the inhibitory effect of Cd2+ stress on tomato seed germination and seedling length. The expression of phytochelatin and transporters-related genes (PCS, NRAMP1, ABCC3, HMA3, and ABCG5) in tomato radicles were significantly increased by MT under Cd2+ stress, showing the positive regulation of MT in transmembrane transport and vacuolar sequestration of Cd2+. In addition, MT alleviated the oxidative damage induced by Cd2+ stress, which was related to the enhanced activities of CAT, APX, and ALDH enzymes apart from its own scavenging ability. Furthermore, MT significantly down-regulated the expressions of abscisic acid (ABA) synthesis genes (NCED1 and NCED2) under Cd2+ stress, and up-regulated the expression of ABA decomposition gene ABA8ox1, leading to the decrease of ABA content, which effectively regulated the GA/ABA ratio and promoted the germination of tomato seeds under Cd2+ stress.

Key words: melatonin, cadmium stress, tomato, seed germination