Abstract
The chloroplast-localized proteins play roles in plant salt stress response, but their mechanisms remain largely unknown. In this study, we screened a yellow leaf mutant, yl1-1, whose shoots exhibited hypersensitivity to salt stress. We mapped YL1 to AT3G57180, which encodes a YqeH-type GTPase. YL1, as a chloroplast stroma-localized protein, could be markedly reduced by high salinity. Upon exposure to high salinity, seedling shoots of yl1-1 and yl1-2 accumulated significantly higher levels of Na+ than wild type. Expression analysis of factors involved in plant salt stress response showed that the expression of ABI4 was increased and HKT1 was evidently suppressed in mutant shoots compared with the wild type under normal growth conditions. Moreover, salinity effects on ABI4 and HKT1 were clearly weakened in the mutant shoots, suggesting that the loss of YL1 function impairs ABI4 and HKT1 expression. Notably, the shoots of yl1-2 abi4 double mutant exhibited stronger resistance to salt stress and accumulated less Na+ levels after salt treatment compared with the yl1-2 single mutant, suggesting the salt-sensitive phenotype of yl1-2 seedlings could be rescued via loss of ABI4 function. These results reveal that YL1 is involved in the salt stress response of seedling shoots through ABI4.
Highlights
High salinity is a serious factor that influences plant productivity
This study focused on shoot phenotypes to elucidate the mechanisms of plant response to salt stress. yl[1], a mutant with severely stunted shoot phenotype under salt stress conditions, was isolated from an ethane methylsulfonate (EMS)-mutagenized library in Col-0 background (Fig. 1a)
YL1, which is mainly localized in the chloroplast stroma (Fig. 3b,c), is a YqeH-type GTPase
Summary
High salinity is a serious factor that influences plant productivity. It affects various aspects of plant physiology and metabolism by inducing osmotic stress and ion toxicity[1]. Arabidopsis seedling shoots usually exhibit pale coloration and stunted phenotypes under salt stress conditions (Fig. 1a). Under salt stress conditions, shoot of yl[1] showed stunted phenotype compared with wild type (Figs 1a and S1), while little differences in root development could be observed (Fig. S1).
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