A single cytosine deletion in the OsPLS1 gene encoding vacuolar-type H+-ATPase subunit A1 leads to premature leaf senescence and seed dormancy in rice.

Xi Yang,Fangmin Cheng,Kunyu Li,Pan Gong,Gang Pan,Fudeng Huang

doi:10.1093/jxb/erw109

Abstract

Leaf senescence is a programmed developmental process orchestrated by many factors, but its molecular regulation is not yet fully understood. In this study, a novel Oryza sativa premature leaf senescence mutant (ospls1) was examined. Despite normal development in early seedlings, the ospls1 mutant leaves displayed lesion-mimics and early senescence, and a high transpiration rate after tillering. The mutant also showed seed dormancy attributable to physical (defect of micropyle structure) and physiological (abscisic acid sensitivity) factors. Using a map-based cloning approach, we determined that a cytosine deletion in the OsPLS1 gene encoding vacuolar H(+)-ATPase subunit A1 (VHA-A1) underlies the phenotypic abnormalities in the ospls1 mutant. The OsPSL1/VHA-A1 transcript levels progressively declined with the age-dependent leaf senescence in both the ospls1 mutant and its wild type. The significant decrease in both OsPSL1/VHA-A1 gene expression and VHA enzyme activity in the ospls1 mutant strongly suggests a negative regulatory role for the normal OsPLS1/VHA-A1 gene in the onset of rice leaf senescence. The ospls1 mutant featured higher salicylic acid (SA) levels and reactive oxygen species (ROS) accumulation, and activation of signal transduction by up-regulation of WRKY genes in leaves. Consistent with this, the ospls1 mutant exhibited hypersensitivity to exogenous SA and/or H2O2 Collectively, these results indicated that the OsPSL1/VAH-A1 mutation played a causal role in premature leaf senescence through a combination of ROS and SA signals. To conclude, OsPLS1 is implicated in leaf senescence and seed dormancy in rice.

Highlights

Vacuolar H+-ATPases (VHAs) are highly conserved enzyme complexes making up 6.5–35% of the total tonoplast protein mass in different plants
We found that OsPLS1/VHA-A1 mutation resulted in leaf senescence through reactive oxygen species (ROS) and salicylic acid (SA) signaling, and seed dormancy due to shallow and compact micropyles in the glumellae and to abscisic acid (ABA) signaling
At the jointing and early heading stage, all of the leaves except the flag leaves of the ospls1 mutant manifested early senescence (Supplementary Fig. S1); and in the flag leaves of the ospls1 mutant at the early heading stage, transmission electron microscopy (TEM) indicated that grana began to break down and osmiophilic plastoglobules increased in size and number (Fig. 1B–E)

Summary

Introduction

Vacuolar H+-ATPases (VHAs) are highly conserved enzyme complexes making up 6.5–35% of the total tonoplast protein mass in different plants. These enzymes are distributed in vacuoles and other membrane-bound organelles such as the Golgi apparatus and endoplasmic reticulum (Schumacher and Krebs, 2010). It is conceivable that VHAs are involved in the generation of a proton gradient and membrane potential which are required to energize secondary transport across the tonoplast (Marty, 1999).

Methods

Results

Conclusion