Expression profile of some important genes related to carbohydrates metabolism under drought stress in bean (Phaseolus vulgaris L.)

This study was carried out to investigate the influence of drought stress during the flowering stage, on the content of water soluble carbohydrates and the expression of genes related to carbohydrate metabolic enzymes (FBPA, FBPase, PGM, PRK, RBCL, RBCS, SBPase, TK, TPI, and GAPDH) in bean (Phaseolus vulgaris L.) leaves. A factorial experiment was conducted based on a randomized complete block design with four replications. Factors included different bean cultivars, Taylor and COS16 (as tolerant cultivars), Khomein and Akhtar (as sensitive cultivars), drought stress included normal irrigation (100% FC) (available water), moderate stress conditions (60% FC), and high stress conditions (30% FC) and stress duration. Significant differences were observed among cultivars and levels of drought stress in carbohydrates content and gene expression. Drought stress caused a decrease in sucrose and an increase in water soluble carbohydrate concentration, glucose, and fructose. These analyses revealed that expression levels of most genes encoding chloroplast enzymes involved in carbon fixation (Calvin cycle) were reduced in the leaves during prolonged drought stress. The expression levels of most genes were higher in tolerant cultivars compared to susceptible ones under drought conditions. Calvin cycle related genes expression showed significant negative correlations with water soluble carbohydrates concentration, glucose, and fructose. In deficient water condition, tolerant cultivars (Taylor and COS16) accumulated more soluble sugars, and Khomein and Akhtar as susceptible cultivars had the lowest soluble sugar in both conditions. The soluble sugar content of different bean cultivars was typically increased, showing that sugar metabolism was influenced greatly by soil water stress.