Drought stress-induced autophagy gene expression is correlated with carbohydrate concentrations in Caragana korshinskii.

Autophagy has been reported to be an adapt function of plant cells under various stresses. In this report, autophagy-related gene expressions and carbohydrate concentrations in Caragana korshinskii leaf cells under drought stress were investigated. Leaf samples of C. korshinskii plants of an estimated 15-year-old were collected from three sites with different drought stress (annual precipitation range, 325.8 to 440.8 mm) at the Loess Plateau in northwestern China. Autophagy was observed in C. korshinskii samples from all three sites and was revealed by autophagosomes in the cytoplasm of mesophyll cells and increased chloroplasts degradation observed by transmission electron microscopy. Furthermore, with the drought stress increase, autophagy-related gene expressions were upregulated and leaf concentration of sucrose was increased, while concentrations of monosaccharide sugars such as glucose, fructose and galactose were decreased. The results suggested that drought stress induced autophagy gene expression, which may serve as a survival mechanism for nutrient remobilisation.

Relative contribution of photorespiration and antioxidative mechanisms in Caragana korshinskii under drought conditions across the Loess Plateau.

The drought-tolerant plant Caragana korshinskii Kom. was used to investigate the relative contribution of photorespiration and antioxidative mechanisms to water-stress adaptations across the Loess Plateau. The samples were collected from Shenmu, Yulin and Dongsheng along with the reduction of rainfall. The results showed the lower leaf water potential and the lower content of O2•- and malondialdehyde (MDA) were found in the plants in drier zone. H2O2 didn't show a significant difference among these sampling sites. Both photorespiratory rate (PR) and net photosynthetic rate (PN) increased with the decrease of rainfall. Low rainfall upregulated the gene expression and activities of photorespiratory enzymes. In addition, ascorbate peroxidase (APX), glutathione peroxidase (GPX) and superoxide dismutase (SOD) activity and reduced glutathione (GSH), ascorbic acid (AsA) contents increased with the decrease of rainfall, whereas catalase (CAT) activity decreased. These results indicate photorespiration could play a protective role for the photosynthetic apparatus from photoinhibition and photodamage under low rainfall levels, which could also act together with the antioxidation system to improve the tolerance to drought in C. korshinskii.