Heat Sensitivity in a Bentgrass Variant. Failure to Accumulate a Chloroplast Heat Shock Protein Isoform Implicated in Heat Tolerance1
Heat Sensitivity in a Bentgrass Variant. Failure to Accumulate a Chloroplast Heat Shock Protein Isoform Implicated in Heat Tolerance1
复制标题
DOI：
10.1104/pp.102.018309
复制
发表时间：
2003-09
期刊：
影响因子：
7.4
通讯作者：
Dongfang Wang;D. Luthe
中科院分区：
文献类型：
--
作者：
Dongfang Wang;D. Luthe
利用组织培养技术培育的两种匍匐翦股颖（Agrostis stolonifera cv palustris）变种，已被用于确定叶绿体定位的小热激蛋白（CP-sHSPs）在耐热性中的作用。从以前的研究结果表明，耐热变体表达两个额外的CP-sHSP异构体不表达的热敏变体，即积累的额外CP-sHSP异构体的遗传与耐热性，和存在的额外异构体的耐热变体提供了更大的保护，光系统II在热应激。为了确定差异表达的基础，我们从两种变体中分离出编码CP-sHSPs的基因，并表征其结构和表达。从耐热突变体中分离到ApHsp26.2和ApHsp26.7a两个基因，从热敏感突变体中分离到ApHsp26.2m、ApHsp26.8和ApHsp26.7b三个基因。来自热敏变体的ApHsp26.2m的序列与ApHsp26.2相同，除了产生提前终止密码子的点突变。因此，ApHsp26.2m的蛋白产物在热敏感株系中没有积累。质谱分析证实，ApHsp26.2编码的CP-sHSP亚型独特的耐热变体。一个相同的突变被检测到的三个亲本系之一，用于开发匍匐鸭茅变种。这表明ApHsp26.2m是从这一亲本遗传而来的，而不是由组织培养过程中发生的突变引起的。由相同基因编码的两种异构体的存在可能是由于在输入叶绿体期间或之后的N-末端氨基酸的差异加工。
Two variants of creeping bentgrass (Agrostis stolonifera cv palustris), developed using tissue culture, have been used to determine the roles of chloroplast-localized small heat shock proteins (CP-sHSPs) in heat tolerance. Results from previous research indicate that the heat-tolerant variant expressed two additional CP-sHSP isoforms not expressed in the heat-sensitive variant, that accumulation of the additional CP-sHSP isoforms was genetically linked to thermotolerance, and that the presence of the additional isoforms in the heat-tolerant variant provided greater protection to photosystem II during heat stress. To determine the basis of the differential expression, we isolated the genes encoding the CP-sHSPs from both variants and characterized their structure and expression. Two genes, ApHsp26.2 and ApHsp26.7a, were isolated from the heat-tolerant variant, and three genes, ApHsp26.2m, ApHsp26.8, and ApHsp26.7b, were isolated from the heat-sensitive variant. The sequence of ApHsp26.2m from the heat-sensitive variant was identical to ApHsp26.2, except for a point mutation that generated a premature stop codon. Therefore, the protein product of ApHsp26.2m did not accumulate in the heat-sensitive line. Mass spectrometry analysis confirmed that ApHsp26.2 encoded for the CP-sHSP isoforms unique to the heat-tolerant variant. An identical mutation was detected in one of the three parental lines used to develop the creeping bentgrass variants. This suggests that ApHsp26.2m was inherited from this parent and did not arise from a mutation that occurred during tissue culture. The presence of two isoforms encoded by the same gene might be due to differential processing of the N-terminal amino acids during or after import into the chloroplast.