Early leaf senescence influences yield and yield quality by affecting plant growth and development. A series of leaf senescence-associated molecular mechanisms have been reported in rice. However, the complex genetic regulatory networks that control leaf senescence need to be elucidated. In this study, an early senescence 2 (es2) mutant was obtained from ethyl methanesulfonate mutagenesis (EMS)-induced mutational library for the Japonica rice cultivar Wuyugeng 7 (WYG7). Leaves of es2 showed early senescence at the seedling stage and became severe at the tillering stage. The contents of reactive oxygen species (ROS) significantly increased, while chlorophyll content, photosynthetic rate, catalase (CAT) activity significantly decreased in the es2 mutant. Moreover, genes which related to senescence, ROS and chlorophyll degradation were up-regulated, while those associated with photosynthesis and chlorophyll synthesis were down-regulated in es2 mutant compared to WYG7. The ES2 gene, which encodes an inositol polyphosphate kinase (OsIPK2), was fine mapped to a 116.73-kb region on chromosome 2. DNA sequencing of ES2 in the mutant revealed a missense mutation, ES2 was localized to nucleus and plasma membrane of cells, and expressed in various tissues of rice. Complementation test and overexpression experiment confirmed that ES2 completely restored the normal phenotype, with chlorophyll contents and photosynthetic rate increased comparable with the wild type. These results reveal the new role of OsIPK2 in regulating leaf senescence in rice and therefore will provide additional genetic evidence on the molecular mechanisms controlling early leaf senescence. The ES2 gene, encoding an inositol polyphosphate kinase localized in the nucleus and plasma membrane of cells, is essential for leaf senescence in rice. Further study of ES2 will facilitate the dissection of the genetic mechanisms underlying early leaf senescence and plant growth.

中文翻译：

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水稻早衰期2，编码肌醇多磷酸激酶，参与叶片衰老。

早期叶片衰老通过影响植物的生长和发育来影响产量和产量质量。水稻中已经报道了一系列与叶片衰老相关的分子机制。但是，需要阐明控制叶片衰老的复杂遗传调控网络。在这项研究中，早衰2（es2）突变体是从甲磺酸乙酯诱变（EMS）诱导的粳稻品种Wuyugeng 7（WYG7）突变库中获得的。es2的叶片在幼苗期显示出早期衰老，而在分er期则变得很严重。es2突变体中活性氧（ROS）含量显着增加，而叶绿素含量，光合速率，过氧化氢酶（CAT）活性显着降低。此外，与衰老，ROS和叶绿素降解有关的基因也被上调，与WYG7相比，es2突变体中与光合作用和叶绿素合成相关的那些被下调。编码肌醇多磷酸激酶（OsIPK2）的ES2基因被精确定位到2号染色体上的116.73-kb区域。突变体中ES2的DNA测序表明存在错义突变，ES2位于细胞核和质膜上，并在水稻的各种组织中表达。补充试验和过表达实验证实，ES2完全恢复了正常表型，叶绿素含量和光合速率增加了与野生型相当的水平。这些结果揭示了OsIPK2在调节水稻叶片衰老中的新作用，因此将为控制早期叶片衰老的分子机制提供更多的遗传证据。ES2基因，编码位于细胞核和质膜中的肌醇多磷酸激酶的编码对于水稻叶片衰老至关重要。ES2的进一步研究将有助于解剖早期叶片衰老和植物生长的遗传机制。