HsfA1a upregulates melatonin biosynthesis to confer cadmium tolerance in tomato plants
HsfA1a upregulates melatonin biosynthesis to confer cadmium tolerance in tomato plants
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DOI：
10.1111/jpi.12387
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发表时间：
2017-03-01
影响因子：
10.3
通讯作者：
Zhou, Jie
中科院分区：
文献类型：
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作者：
Cai, Shu-Yu;Zhang, Yun;Zhou, Jie
褪黑素调节植物对各种生物和非生物胁迫的广泛反应，但这些胁迫对褪黑素生物合成的上游调控在很大程度上仍不清楚。在这里，我们证明了转录因子热休克因子A1a(HsfA1a)赋予番茄对镉(Cd)的耐性，部分是通过它在Cd胁迫下诱导褪黑素生物合成的积极作用。对叶片表型、叶绿素含量和光合作用效率的分析表明，HsfA1a基因的沉默降低了植物对Cd的耐性，而其过表达则增强了植物对Cd的耐性。Cd胁迫下，HsfA1a沉默植株褪黑激素水平降低，HsfA1a过表达促进褪黑激素积累和褪黑素生物合成基因咖啡酸O-甲基转移酶1(COMT1)的表达。体外电泳迁移率改变分析和体内染色质免疫沉淀结合定量聚合酶链式反应分析都表明HsfA1a与COMT1基因启动子结合。同时，Cd胁迫诱导了热休克蛋白(HSPs)的表达，在HsfA1a沉默的植株中，HSPs的表达受到抑制，而在Cd胁迫下，HsfA1a高表达的植株诱导的HSPs的表达更为强烈。COMT1沉默降低了HsfA1a诱导的Cd耐受性和HsfA1a过表达植物中褪黑激素的积累。此外，在Cd胁迫下COMT1沉默的野生型或HsfA1a过表达的植物中，HsfA1a诱导的HSPs的表达被部分抑制。这些结果表明，HsfA1a通过激活COMT1基因的转录和诱导褪黑素的积累部分上调HSPs的表达来赋予Cd耐受性。
Melatonin regulates broad aspects of plant responses to various biotic and abiotic stresses, but the upstream regulation of melatonin biosynthesis by these stresses remains largely unknown. Herein, we demonstrate that transcription factor heat-shock factor A1a (HsfA1a) conferred cadmium (Cd) tolerance to tomato plants, in part through its positive role in inducing melatonin biosynthesis under Cd stress. Analysis of leaf phenotype, chlorophyll content, and photosynthetic efficiency revealed that silencing of the HsfA1a gene decreased Cd tolerance, whereas its overexpression enhanced plant tolerance to Cd. HsfA1a-silenced plants exhibited reduced melatonin levels, and HsfA1a overexpression stimulated melatonin accumulation and the expression of the melatonin biosynthetic gene caffeic acid O-methyltransferase 1 (COMT1) under Cd stress. Both an in vitro electrophoretic mobility shift assay and in vivo chromatin immunoprecipitation coupled with qPCR analysis revealed that HsfA1a binds to the COMT1 gene promoter. Meanwhile, Cd stress induced the expression of heat-shock proteins (HSPs), which was compromised in HsfA1a-silenced plants and more robustly induced in HsfA1a-overexpressing plants under Cd stress. COMT1 silencing reduced HsfA1a-induced Cd tolerance and melatonin accumulation in HsfA1a-overexpressing plants. Additionally, the HsfA1a-induced expression of HSPs was partially compromised in COMT1-silenced wild-type or HsfA1a-overexpressing plants under Cd stress. These results demonstrate that HsfA1a confers Cd tolerance by activating transcription of the COMT1 gene and inducing accumulation of melatonin that partially upregulates expression of HSPs.