Abstract
BackgroundPlant 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.ResultsWe 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.ConclusionsWe 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.
Highlights
Plant senescence is a complicated process involving multiple regulations, such as temperature, light, reactive oxygen species (ROS), endogenous hormone levels, and diseases
We measured the expression of two chlorophyll degradation-related genes (CDGs), stay-green (SGR) and red chlorophyll catabolite reductase 1 (RCCR1), and two other senescence-associated genes (SAGs), Os157 and Os185, in the fully expanded leaves of the nbl1 mutant and wild-type plants
We found that these four genes were significantly upregulated in the nbl1 mutant compared to wild-type plants (Fig. 1e-h)
Summary
Plant senescence is a complicated process involving multiple regulations, such as temperature, light, reactive oxygen species (ROS), endogenous hormone levels, and diseases. 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. A natural process involving programmed cell death in plant development, facilitates nutrient remobilization and plays a crucial role in crop yield (Lim et al, 2007; Wu et al, 2012b). In plant-pathogen interactions, pPCD is an effective strategy to limit pathogen spread, especially for biotrophic pathogens (Glazebrook, 2005)
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