辣椒金属伴侣蛋白基因CaHPP7提高植物对铜和热胁迫的抗性

A Metallochaperone Gene CaHPP7 from Pepper Improves Plants Tolerance to Both Copper and Heat Stresses

金属伴侣蛋白在植物抵抗重金属胁迫和低温、干旱、高盐等非生物胁迫中发挥重要作用,但其应对热胁迫时发挥作用的报道还很少。前期研究从辣椒中分离到一个能够响应热胁迫的金属伴侣蛋白基因CaHPP7,通过生物信息学和定量分析发现该基因的氨基酸序列含有1个HMA结构域,且其表达受高温、Cu^(2+)、Cd^(2+)等重金属,以及ABA(Abscisic acid)、MeJA(Jasmonic acid methylester)和SA(Salicylic acid)等外源信号物质的诱导。为了进一步明确CaHPP7基因在植物重金属和热胁迫抗性形成中的功能,利用基因沉默和过表达技术改变Ca HPP7的表达水平。结果显示,基因沉默表达后,辣椒对铜和热胁迫的抗性都降低,表现为离体叶圆片叶绿素含量下降程度显著高于未沉默植株;而基因过表达后,拟南芥对铜和热胁迫的抗性都升高,其中热胁迫下表现为幼苗存活率高于对照,叶圆片叶绿素含量减少程度低于对照;铜胁迫下表现为种子发芽率高于对照,幼苗生长的受抑制程度和叶圆片叶绿素含量下降程度均低于对照。故推测CaHPP7基因在植物应对高温和铜胁迫的过程中起正调控作用。本研究结果将为进一步揭示植物抗逆性形成的分子机制提供理论依据,也将为农作物抗逆新品种的选育提供参考。

A metallochaperone protein plays important roles in plant fighting against heavy-metal stress and other abiotic stresses,such as low temperature,drought and salinity.However,the involvement of metallochaperone proteins in plant heat tolerance is rarely reported.In previous research work,a heat-induced metallochaperone protein gene CaHPP7 was isolated from pepper.By bioinformatics and quantitative analysis,an HMA domain was identified in the amino acid sequence of CaHPP7,and the expression of CaHPP7 was induced by high temperature,heavy metals Cu^(2+)and Cd^(2+),and exogenous signal substances including ABA(Abscisic acid),MeJA(Jasmonic acid methylester),and SA(Salicylic acid).In order to further clarify the function of CaHPP7 gene in plant tolerance to heat and heavy-metal stresses,gene silencing and overexpression techniques were used to change the expression level of CaHPP7.The results showed that the silenced expression of CaHPP7 reduced the tolerance to heat and copper stresses in pepper.The chlorophyll content of isolated leaf discs was significantly lower than that of unsilenced plants.While the overexpression of CaHPP7 increased Arabidopsis thaliana tolerance to these two abiotic stresses,in which under heat stress,the survival rate of seedlings was higher than that of the control,and the reduction degree of chlorophyll content of leaf discs was lower than that of the control;under copper stress,the seed germination rate was higher than that of the control,and the degree of growth inhibition of the seedlings and chlorophyll content reduction of leaf discs were lower than those of the control.Therefore,we speculate that CaHPP7 gene plays a positive role in plant dealing with the adverse effects from heat and copper stresses.These results will lay a theoretic foundation for the uncovering of the molecular mechanism of plant tolerance to abiotic stresses,and provide a reference for the breeding of crop varieties with stress-tolerance.