AtDPG1 is involved in the salt stress response of Arabidopsis seedling through ABI4

Although the genes controlling chloroplast development play important roles in plant responses to environmental stresses, the molecular mechanisms remain largely unclear. In this study, an Arabidopsis mutant dpg1 (delayed pale-greening1) with a chloroplast development defect was studied. By using quantitative RT-PCR and histochemical GUS assays, we demonstrated that AtDPG1 was mainly expressed in the green tissues of Arabidopsis seedlings and could be induced by salt stress. Phenotypic analysis showed that mutation in AtDPG1 lead to an enhanced sensitivity to salt stress in Arabidopsis seedlings. Further studies demonstrated that disruption of the AtDPG1 in Arabidopsis increases its sensitivity to salt stress in an ABA-dependent manner. Moreover, expression levels of various stress-responsive and ABA signal-related genes were remarkably altered in the dpg1 plants under NaCl treatment. Notably, the transcript levels of ABI4 in dpg1 mutant increased more significantly than that in wild type plants under salt conditions. The seedlings of dpg1/abi4 double mutant exhibited stronger resistance to salt stress after salt treatment compared with the dpg1 single mutant, suggesting that the salt-hypersensitive phenotype of dpg1 seedlings could be rescued via loss of ABI4 function. These results reveal that AtDPG1 is involved in the salt stress response of Arabidopsis seedling through ABI4.