College of Life Science, State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an, Shandong 271018, PR China.
College of Life Science, State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an, Shandong 271018, PR China
J Exp Bot. 2015 Jun;66(11):3027-40. doi: 10.1093/jxb/erv102. Epub 2015 Mar 23.
Photosynthesis is one of the biological processes most sensitive to heat stress in plants. Carbon assimilation, which depends on ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), is one of the major sites sensitive to heat stress in photosynthesis. In this study, the roles of a tomato (Solanum lycopersicum) chloroplast-targeted DnaJ protein (SlCDJ2) in resisting heat using sense and antisense transgenic tomatoes were examined. SlCDJ2 was found to be uniformly distributed in the thylakoids and stroma of the chloroplasts. Under heat stress, sense plants exhibited higher chlorophyll contents and fresh weights, and lower accumulation of reactive oxygen species (ROS) and membrane damage. Moreover, Rubisco activity, Rubisco large subunit (RbcL) content, and CO2 assimilation capacity were all higher in sense plants and lower in antisense plants compared with wild-type plants. Thus, SlCDJ2 contributes to maintenance of CO2 assimilation capacity mainly by protecting Rubisco activity under heat stress. SlCDJ2 probably achieves this by keeping the levels of proteolytic enzymes low, which prevents accelerated degradation of Rubisco under heat stress. Furthermore, a chloroplast heat-shock protein 70 was identified as a binding partner of SlCDJ2 in yeast two-hybrid assays. Taken together, these findings establish a role for SlCDJ2 in maintaining Rubisco activity in plants under heat stress.
光合作用是植物对热应激最敏感的生物过程之一。碳同化，依赖于核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco），是光合作用中对热应激敏感的主要部位之一。在这项研究中，使用 sense 和 antisense 转基因番茄研究了番茄（Solanum lycopersicum）叶绿体靶向 DnaJ 蛋白（SlCDJ2）在耐热中的作用。发现 SlCDJ2 在类囊体和叶绿体基质中均匀分布。在热应激下，sense 植株表现出更高的叶绿素含量和鲜重，更低的活性氧（ROS）积累和膜损伤。此外，与野生型植株相比，sense 植株的 Rubisco 活性、Rubisco 大亚基（RbcL）含量和 CO2 同化能力均较高，而 antisense 植株则较低。因此，SlCDJ2 通过在热应激下保护 Rubisco 活性来维持 CO2 同化能力。SlCDJ2 可能通过保持蛋白酶水平较低来实现这一点，这可以防止 Rubisco 在热应激下加速降解。此外，在酵母双杂交试验中鉴定出一种叶绿体热休克蛋白 70 是 SlCDJ2 的结合伴侣。总之，这些发现确立了 SlCDJ2 在植物耐热过程中维持 Rubisco 活性的作用。
