Xu Jiangmin, Ji Zhiyuan, Wang Chunlian, Xu Feifei, Wang Fujun, Zheng Yuhan, Tang Yongchao, Wei Zheng, Zhao Tianyong, Zhao Kaijun
National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing, China.
State Key Laboratory of Crop Stress Biology for Arid Areas, College of Life Sciences, Northwest A&F University, Xianyang, China.
Front Plant Sci. 2022 May 26;13:918673. doi: 10.3389/fpls.2022.918673. eCollection 2022.
Transmembrane kinases (TMKs) play important roles in plant growth and signaling cascades of phytohormones. However, its function in the regulation of early leaf senescence (ELS) of plants remains unknown. Here, we report the molecular cloning and functional characterization of the gene which encodes a protein belongs to the TMK family and controls chloroplast development and leaf senescence in rice ( L.). The () mutant displays water-soaked spots which subsequently developed into necrotic symptoms at the tillering stage. Moreover, exhibits slightly rolled leaves with irregular epidermal cells, decreased chlorophyll contents, and defective stomata and chloroplasts as compared with the wild type. Map-based cloning revealed that encodes transmembrane kinase TMK1. Genetic complementary experiments verified that a Leu396Pro amino acid substitution, residing in the highly conserved region of leucine-rich repeat (LRR) domain, was responsible for the phenotypes of . was constitutively expressed in all tissues and its encoded protein is localized to the plasma membrane. Mutation of led to hyper-accumulation of reactive oxygen species (ROS), more severe DNA fragmentation, and cell death than that of the wild-type control. In addition, we found that the expression of senescence-associated genes (SAGs) was significantly higher, while the expression of genes associated with chloroplast development and photosynthesis was significantly downregulated in as compared with the wild type. Taken together, our results demonstrated that OsWSS1, a member of TMKs, plays a vital role in the regulation of ROS homeostasis, chloroplast development, and leaf senescence in rice.
跨膜激酶（TMKs）在植物生长和植物激素信号级联反应中发挥着重要作用。然而，其在植物早期叶片衰老（ELS）调控中的功能尚不清楚。在此，我们报道了一个基因的分子克隆和功能特性，该基因编码一种属于TMK家族的蛋白质，并控制水稻（Oryza sativa L.）的叶绿体发育和叶片衰老。OsWSS1（Oryza sativa water-soaked spot1）突变体在分蘖期出现水渍斑，随后发展为坏死症状。此外，与野生型相比，OsWSS1表现出叶片轻微卷曲，表皮细胞不规则，叶绿素含量降低，气孔和叶绿体有缺陷。图位克隆显示，OsWSS1编码跨膜激酶TMK1。遗传互补实验证实，位于富含亮氨酸重复序列（LRR）结构域高度保守区域的Leu396Pro氨基酸取代是导致OsWSS1表型的原因。OsWSS1在所有组织中组成型表达，其编码的蛋白质定位于质膜。与野生型对照相比，OsWSS1突变导致活性氧（ROS）过度积累、更严重的DNA片段化和细胞死亡。此外，我们发现与野生型相比，衰老相关基因（SAGs）在OsWSS1中的表达显著更高，而与叶绿体发育和光合作用相关的基因表达则显著下调。综上所述，我们的结果表明，TMKs成员OsWSS1在水稻ROS稳态、叶绿体发育和叶片衰老的调控中起着至关重要的作用。
