Background

Plant senescence is a complicated process involving multiple regulations, such as temperature, light, reactive oxygen species (ROS), endogenous hormone levels, and diseases. Although many such genes have been characterized to understand the process of leaf senescence, there still remain many unknowns, and many more genes need to be characterized.

Results

We identified a rice mutant nbl1 with a premature leaf senescence phenotype. The causative gene, OsNBL1, encodes a small protein with 94 amino acids, which is conserved in monocot, as well as dicot plants. Disruption of OsNBL1 resulted in accelerated dark-induced leaf senescence, accompanied by a reduction in chlorophyll content and up-regulation of several senescence-associated genes. Notably, the nbl1 mutant was more susceptible to rice blast and bacterial blight but more tolerant to sodium chloride. Several salt-induced genes, including HAK1, HAK5, and three SNAC genes, were also up-regulated in the nbl1 mutant. Additionally, the nbl1 mutant was more sensitive to salicylic acid. Plants overexpressing OsNBL1 showed delayed dark-induced senescence, consistent with a higher chlorophyll content compared to wild-type plants. However, the overexpression plants were indistinguishable from the wild-types for resistance to the rice blast disease. OsNBL1 is a multi-organelle localized protein and interacts with OsClpP6, which is associated with senescence.

Conclusions

We described a novel leaf senescence mutant nbl1 in rice. It is showed that OsNBL1, a multi-organelle localized protein which interacts with a plastidic caseinolytic protease OsClpP6, is essential for controlling leaf senescence, disease resistance, and salt tolerance.

中文翻译：

---

OsNBL1，一种多器官定位蛋白，在水稻衰老，抗病性和耐盐性中起重要作用

背景

植物衰老是一个复杂的过程，涉及多个法规，例如温度，光照，活性氧（ROS），内源激素水平和疾病。尽管已经对许多此类基因进行了表征以了解叶片衰老的过程，但仍然存在许多未知数，还需要对许多其他基因进行表征。

结果

我们确定了水稻突变体nbl1具有过早的叶片衰老表型。致病基因OsNBL1编码一个具有94个氨基酸的小蛋白质，该蛋白质在单子叶植物和双子叶植物中都保守。OsNBL1的破坏导致黑暗诱导的叶片衰老加速，并伴随着叶绿素含量的降低和几种衰老相关基因的上调。值得注意的是，nbl1突变体对稻瘟病和细菌性疫病更敏感，但对氯化钠的耐受性更高。几个盐诱导的基因，包括HAK 1，HAK 5和三个SNAC基因，在nbl1中也被上调突变体。此外，nbl1突变体对水杨酸更敏感。过表达OsNBL1的植物显示出延迟的黑暗诱导衰老，与野生型植物相比，叶绿素含量更高。然而，对于稻瘟病的抗性，过表达植物与野生型没有区别。OsNBL1是一种多细胞器定位蛋白，并与OsClpP6相互作用，后者与衰老有关。

结论

我们描述了水稻中一种新的叶片衰老突变体nbl1 。结果表明，OsNBL1是一种多细胞器定位蛋白，与质溶性酪蛋白水解蛋白酶OsClpP6相互作用，对于控制叶片衰老，抗病性和耐盐性至关重要。