褪黑素促进镉胁迫下番茄种子萌发的调控机理

doi:10.11983/CBB22202

摘要/Abstract

摘要： 土壤镉(Cd²⁺)污染严重制约设施蔬菜的产量和品质。褪黑素(MT)可以增强植株对多种逆境的抗性, 然而Cd²⁺胁迫下MT调控番茄(Solanum lycopersicum)种子萌发的下游信号尚不清楚。该研究以番茄野生型Alisa Craig种子为材料, 探究不同浓度Cd²⁺处理及外源MT对番茄种子萌发的调控效应。结果表明, 0.5 mmol·L^-1以上的Cd²⁺处理显著抑制番茄种子的萌发和幼苗生长。用0.15 mmol·L^-1 MT浸种可降低种子萌发后地下部和地上部的Cd²⁺含量, 有效缓解Cd²⁺胁迫对番茄种子萌发和幼苗生长的抑制作用。MT上调了番茄胚根中植物螯合肽和转运蛋白基因(PCS、NRAMP1、ABCC3、HMA3与ABCG5)的表达, 促进Cd²⁺的跨膜转运以及液泡隔离。此外, MT减轻了Cd²⁺诱导的氧化损伤, 除褪黑素自身的抗氧化作用外, 也与抗氧化酶(CAT、APX与ALDH)活性的增强相关。进一步分析表明, MT显著下调了Cd²⁺胁迫下脱落酸(ABA)合成基因(NCED1和NCED2)的表达, 并上调了ABA分解基因ABA8ox1的表达, 降低ABA含量, 从而有效调节赤霉素/脱落酸(GA/ABA)的比值, 促进Cd²⁺胁迫下番茄种子的萌发。

关键词: 褪黑素, 镉胁迫, 番茄, 种子萌发

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

蔡淑钰, 刘建新, 王国夫, 吴丽元, 宋江平. 褪黑素促进镉胁迫下番茄种子萌发的调控机理. 植物学报, 2023, 58(5): 720-732.

Cai Shuyu, Liu Jianxin, Wang Guofu, Wu Liyuan, Song Jiangping. Regulatory Mechanism of Melatonin on Tomato Seed Germination Under Cd²⁺ Stress. Chinese Bulletin of Botany, 2023, 58(5): 720-732.

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链接本文: https://www.chinbullbotany.com/CN/10.11983/CBB22202

https://www.chinbullbotany.com/CN/Y2023/V58/I5/720

图/表 11

图1 Cd2+浓度梯度对番茄种子萌发与幼苗质量的影响 (A) 发芽3天番茄种子的萌发情况(bars=1 cm); (B) 发芽3天番茄种子的发芽率; (C) 发芽5天番茄幼苗表型(bar=1 cm); (D) 发芽5天番茄幼苗长度。不同小写字母表示处理间差异显著(P<0.05)。

Figure1 Effect of cadmium concentrations on seed germination and seedling growth of tomato (A) Germination phenotypes of tomato seeds 3 days after germination(bars=1 cm); (B) Germination rate of tomato seeds 3 days after germination; (C) Phenotypes of tomato seedlings 5 days after germination (bar=1 cm); (D) Seedling length of tomato 5 days after germination. Different lowercase letters indicate significant differences among different treatments (P<0.05).

图2 褪黑素(MT)对Cd2+胁迫下番茄种子萌发的影响 (A) 发芽3天种子的萌发情况(bars=1 cm); (B) 发芽率; (C) 发芽5天番茄幼苗的表型(bar=1 cm); (D) 幼苗长度。不同小写字母表示处理间差异显著(P<0.05)。Control: 0 mmol·L-1 Cd2+; Cd2+: 0.5 mmol·L-1 Cd2+; Control/MT: 0 mmol·L-1 Cd2++0.15 mmol·L-1 MT; Cd2+/MT: 0.5 mmol·L-1 Cd2++0.15 mmol·L-1 MT

Figure 2 Effects of melatonin (MT) on tomato seed germination under Cd2+ stress (A) Germination phenotypes of seeds 3 days after germination(bars=1 cm); (B) Germination rate; (C) Phenotypes of tomato seedlings 5 days after germination (bar=1 cm); (D) Seedling length. Different lowercase letters indicate significant differences among different treatments (P<0.05).

图3 褪黑素(MT)处理对Cd2+胁迫下番茄种子萌发过程中内源褪黑素代谢的影响 (A) MT含量; (B) 氨酸脱羧酶(TDC)活性; (C) 色胺-5-羟化酶(T5H)活性; (D) 5-羟色胺-N-乙酰基转移酶(SNAT)活性; (E) N-乙酰基- 5-羟色胺-甲基转移酶(ASMT)活性; (F) 咖啡酸-O-甲基转移酶(COMT)活性。不同小写字母和*表示处理间差异显著(P<0.05)。Control、Cd2+和Cd2+/MT同图2。

Figure 3 Effects of melatonin (MT) treatment on endogenous melatonin metabolism during tomato seed germination under Cd2+ stress (A) MT content; (B) Tryptophan decarboxylase (TDC) activity; (C) Tryptamine-5-hydroxylase (T5H) activity; (D) 5-serotonin-N-acetyltransferae (SNAT) activity; (E) N-acetyl-5-serotonin-methyltransferase (ASMT) activity; (F) Caffeicacid-O-me- thyltransferase (COMT) activity. Different lowercase letters and * indicate significant differences among different treatments (P<0.05). Control, Cd2+, and Cd2+/MT are the same as shown in Figure 2.

表1 Cd2+胁迫下番茄种子萌发过程中Cd2+积累情况

Table 1 Cd2+ accumulation of tomato seeds during germination under Cd2+ stress

Treatment	Cd²⁺content in underground parts (mg·kg^-1 DW)		Cd²⁺ content in above-ground parts (mg·kg^-1 DW)
Treatment	3 d	5 d	3 d	5d
Control	0.074±0.004 c	0.098±0.012 c	0.034±0.005 b	0.047±0.003 c
Cd²⁺	0.138±0.011 a	0.176±0.009 a	0.041±0.006 a	0.068±0.004 a
Cd²⁺/MT	0.097±0.007 b	0.126±0.007 b	0.042±0.005 a	0.054±0.007 b

图4 褪黑素(MT)处理对Cd2+胁迫下番茄种子萌发过程中Cd2+吸收、转运以及螯合代谢酶基因表达的影响 Control、Cd2+和Cd2+/MT同图2。

Figure 4 Effects of melatonin (MT) on the gene expression of Cd2+ uptake, transport and chelating metabolic enzymes in tomato seed germination under Cd2+ stress Control, Cd2+, and Cd2+/MT are the same as shown in Figure 2.

表2 褪黑素(MT)处理对Cd2+胁迫下番茄种子萌发过程中过氧化氢(H2O2)、超氧阴离子(O2-. )与丙二醛(MDA)积累的影响

Table 2 Effects of melatonin (MT) on the accumulation of H2O2, O2-. and malonaldehyde (MDA) in tomato seed germination under Cd2+ stress

Treatment	H₂O₂(μmol·g^-1 FW)	O₂^-.(μmol·g^-1 FW)	MDA (μmol·g^-1 FW)
Control	13.24±0.714 c	2.43±0.154 b	6.26±0.514 c
Cd²⁺	25.37±1.325 a	4.79±0.328 a	10.13±0.758 a
Cd²⁺/MT	20.13±1.628 b	4.13±0.376 a	8.24±0.811 b

表3 褪黑素(MT)处理对Cd2+胁迫下番茄种子萌发过程中抗氧化酶活性的影响

Table 3 Effects of melatonin (MT) on antioxidant enzyme activities during tomato seed germination under Cd2+ stress

Treatment	SOD (U·g^-1 FW)	POD (U·g^-1 FW)	CAT (U·g^-1 FW)	APX (U·g^-1 FW)	ALDH (U·g^-1 FW)
Control	2.13±0.175 b	0.105±0.078 b	3.57±0.295 c	0.274±0.037 c	1.37±0.116 c
Cd²⁺	2.74±0.213 a	0.157±0.024 a	4.19±0.182 b	0.357±0.042 b	2.17±0.133 b
Cd²⁺/MT	2.63±0.146 a	0.142±0.021 a	5.12±0.411 a	0.408±0.026 a	2.58±0.179 a

图5 褪黑素(MT)对Cd2+胁迫下番茄种子萌发过程中抗氧化酶基因表达的影响 Control、Cd2+和Cd2+/MT同图2。

Figure 5 Effects of melatonin (MT) on the expression of antioxidant enzyme genes in tomato seed germination under Cd2+ stress Control, Cd2+, and Cd2+/MT are the same as shown in Figure 2.

图6 褪黑素(MT)处理对Cd2+胁迫下番茄种子萌发过程中赤霉素(GA)代谢的影响 (A) 赤霉素含量; (B) 赤霉素-3-氧化酶(GA3ox)活性; (C) 赤霉素-20-氧化酶(GA20ox)活性; (D) 赤霉素-2-氧化酶(GA2ox)活性。不同小写字母和*表示在0.05水平差异显著。Control、Cd2+和Cd2+/MT同图2。

Figure 6 Effects of melatonin (MT) on gibberellin acid (GA) metabolism during tomato seed germination under Cd2+stress (A) GA content; (B) GA-3-oxidase (GA3ox) activity; (C) GA-20-oxidase (GA20ox) activity; (D) GA-2-oxidase (GA2ox) activity. Different lowercase letters and * indicate significant differences at 0.05 level. Control, Cd2+, and Cd2+/MT are the same as shown in Figure 2.

图7 褪黑素(MT)处理对Cd2+胁迫下番茄种子萌发过程中脱落酸(ABA)代谢的影响 (A) ABA含量; (B) 9-顺式-环氧类胡萝卜素二加氧酶(NCED)活性; (C) 玉米黄质环氧化酶(ZEP)活性; (D) 脱落酸醛氧化酶(AAO)活性; (E) 脱落酸-8-羟化酶(ABA8ox)活性。不同小写字母和*表示在0.05水平差异显著。Control、Cd2+和Cd2+/MT同图2。

Figure 7 Effects of melatonin (MT) on abscisic acid (ABA) metabolism during tomato seed germination under Cd2+stress (A) Abscisic acid content; (B) 9-cis-epoxycarotenoid dioxygenase (NCED) activity; (C) Zeaxanthin epoxidase (ZEP) activity; (D) ABA-aldehyde oxidase (AAO) activity; (E) ABA-8-hydroxylase (ABA8ox) activity. Different lowercase letters and * indicate significant differences at 0.05 level. Control, Cd2+, and Cd2+/MT are the same as shown in Figure 2.

图8 褪黑素(MT)处理对赤霉素(GA)与脱落酸(ABA)代谢基因表达的影响 Control、Cd2+和Cd2+/MT同图2。

Figure 8 Effects of melatonin (MT) on gene expression of gibberellin (GA) and abscisic acid (ABA) metabolism Control, Cd2+, and Cd2+/MT are the same as shown in Figure 2.

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