State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, 712100, Shaanxi, P. R. China.
BMC Plant Biol. 2020 Dec 10;20(1):555. doi: 10.1186/s12870-020-02762-0.
The degradation of intracellular proteins plays an essential role in plant responses to stressful environments. ClpS1 and E3 ubiquitin ligase function as adaptors for selecting target substrates in caseinolytic peptidase (Clp) proteases pathways and the 26S proteasome system, respectively. Currently, the role of E3 ubiquitin ligase in the plant immune response to pathogens is well defined. However, the role of ClpS1 in the plant immune response to pathogens remains unknown.
Here, wheat (Triticum aestivum) ClpS1 (TaClpS1) was studied and resulted to encode 161 amino acids, containing a conserved ClpS domain and a chloroplast transit peptide (1-32 aa). TaClpS1 was found to be specifically localized in the chloroplast when expressed transiently in wheat protoplasts. The transcript level of TaClpS1 in wheat was significantly induced during infection by Puccinia striiformis f. sp. tritici (Pst). Knockdown of TaClpS1 via virus-induced gene silencing (VIGS) resulted in an increase in wheat resistance against Pst, accompanied by an increase in the hypersensitive response (HR), accumulation of reactive oxygen species (ROS) and expression of TaPR1 and TaPR2, and a reduction in the number of haustoria, length of infection hypha and infection area of Pst. Furthermore, heterologous expression of TaClpS1 in Nicotiana benthamiana enhanced the infection by Phytophthora parasitica.
These results suggest that TaClpS1 negatively regulates the resistance of wheat to Pst.
细胞内蛋白质的降解在植物应对胁迫环境的过程中起着至关重要的作用。ClpS1 和 E3 泛素连接酶分别作为衔接蛋白，在乳蛋白酶体途径和 26S 蛋白酶体系统中选择靶底物。目前，E3 泛素连接酶在植物对病原体的免疫反应中的作用已得到充分证实。然而，ClpS1 在植物对病原体的免疫反应中的作用尚不清楚。
本研究对小麦 ClpS1（TaClpS1）进行了研究，结果表明 TaClpS1 编码 161 个氨基酸，包含一个保守的 ClpS 结构域和一个质体转运肽（1-32 aa）。瞬时表达于小麦原生质体时，TaClpS1 被发现特异性定位于叶绿体。在小麦感染条锈菌（Puccinia striiformis f. sp. tritici，Pst）时，TaClpS1 的转录水平显著上调。通过病毒诱导的基因沉默（VIGS）敲低 TaClpS1 导致小麦对 Pst 的抗性增强，同时伴随着超敏反应（HR）的增加、活性氧（ROS）的积累、TaPR1 和 TaPR2 的表达增加，以及吸器数量减少、感染菌丝长度和 Pst 感染面积的减少。此外，在本氏烟中异源表达 TaClpS1 增强了对寄生疫霉的侵染。
这些结果表明 TaClpS1 负调控小麦对 Pst 的抗性。
