Leaf senescence induced by EGY1 defection was partially restored by glucose in Arabidopsis thaliana

Ethylene-dependent gravitropism-deficient and yellow-green 1 (EGY1) protein is required for chloroplast development and photosynthesis conduction. The egy1 deletion mutants have a yellow-green phenotype and reduced granal thylakoids. Furthermore, the yellow-green phenotype of egy1 mutants is more obvious than that of wild-type (WT) plants with increasing leaf age, suggesting an early senescence in the egy1 mutants. However, the relationship between EGY1 functions and leaf senescence still remains poorly understood.

We observed that egy1 mutant leaves were more yellow than those of WT (the same age) in Arabidopsis thaliana. In accompany with this phenotype, leaf survival, chlorophyll content, Fv/Fm and soluble protein content decreased, and ion leakage increased significantly in egy1 mutants compared to WT plants. At molecular level, the expressions of senescence-associated genes increased, and photosynthesis genes decreased significantly in the mutants compared to those in WT plants. Furthermore, after darkness treatment, the yellow-green phenotype of egy1 mutants was more obvious than that of WT. These results indicate that the loss-of-function of egy1 gene induces leaf senescence in A. thaliana. In addition, our results showed that the yellow-green phenotype, chlorophyll content and ion leakage of egy1 mutants was partially restored after exogenously applied glucose for 5 weeks. At the same time, the expression of hexokinase 1 (HXK1) and/or senescence-associated gene 12 (SAG12) in egy1 mutants growing on 2 % glucose was lower than that in egy1 mutants without glucose.

EGY1-defection induced leaf senescence and this senescence was partially restored by glucose in A. thaliana.