PDF(Pubmed)
Abstract：
Heat stress causes dysfunction of the carbon-assimilation metabolism. As a member of Calvin-Benson-Bassham (CBB) cycle, the chloroplast triose phosphate isomerases (TPI) catalyse the interconversion of glyceraldehyde 3-phosphate (GAP) and dihydroxyacetone phosphate (DHAP). The tomato (Solanum lycopersicum) genome contains two individual SlTPI genes, Solyc10g054870 and Solyc01g111120, which encode the chloroplast-located proteins SlTPI1 and SlTPI2, respectively. The tpi1 and tpi2 single mutants had no visible phenotypes, but the leaves of their double mutant lines tpi1tpi2 had obviously reduced TPI activity and displayed chlorotic variegation, dysplasic chloroplasts and lower carbon-assimilation efficiency. In addition to altering carbon metabolism, proteomic data showed that the loss of both SlTPI1 and SlTPI2 severely affected photosystem proteins, reducing photosynthetic capacity. None of these phenotypes was evident in the tpi1 or tpi2 single mutants, suggesting that SlTPI1 and SlTPI2 are functionally redundant. However, the two proteins differed in their responses to heat stress; the protein encoded by the heat-induced SlTPI2 showed a higher level of thermotolerance than that encoded by the heat-suppressed SlTPI1. Notably, heat-induced transcription factors, SlWRKY21 and SlHSFA2/7, which negatively regulated SlTPI1 expression and positively regulated SlTPI2 expression, respectively. Our findings thus reveal that SlTPI1 and SlTPI2 have different thermostabilities and expression patterns in response to heat stress, which have the potential to be applied in thermotolerance strategies in crops.
摘要：
热应激导致碳同化代谢的功能障碍。作为卡尔文-本森-巴斯舍姆（CBB）周期的成员，叶绿体磷酸丙糖异构酶（TPI）催化3-磷酸甘油醛（GAP）和磷酸二羟基丙酮（DHAP）的相互转化。番茄（Solanumlycopersicum）基因组包含两个单独的SlTPI基因，Solyc10g054870和Solyc01g111120，分别编码叶绿体定位蛋白SlTPI1和SlTPI2。tpi1和tpi2单突变体没有可见的表型,但是它们的双突变系tpi1tpi2的叶片具有明显的降低的TPI活性并表现出褪绿变异，发育不良的叶绿体和较低的碳同化效率。除了改变碳代谢，蛋白质组数据表明，SlTPI1和SlTPI2的丢失严重影响了光系统蛋白，降低光合能力。这些表型在tpi1或tpi2单突变体中都不明显，这表明SlTPI1和SlTPI2在功能上是多余的。然而,这两种蛋白质对热应激的反应不同；由热诱导的SlTPI2编码的蛋白质显示出比由热抑制的SlTPI1编码的蛋白质更高的耐热性。值得注意的是,热诱导转录因子，SlWRKY21和SlHSFA2/7负调控SlTPI1表达和正调控SlTPI2表达，分别。因此，我们的发现表明，SlTPI1和SlTPI2在响应热应激时具有不同的热稳定性和表达模式，有潜力应用于作物的耐热性策略。
