Effect of Drought Stress on Photosynthetic Parameters and Gene Expression in Brassica juncea L. (Czern. and Coss.)

Drought stress limits the plant growth resulting in drastic decline in the photosynthetic yield globally. The present investigation was carried out to study the expression of drought induced pp2c and lhcb genes in Brassica juncea cvs. RH0116 (drought tolerant) and RH8812 (drought sensitive) via semi-quantitative RT-PCR using actin as constitutive gene. Brassica plants were grown in net house and subjected to drought stress by withholding water at flowering stage. We observed that pp2c gene was upregulated and was expressed in both shoots and roots during drought. The drought tolerant genotype exhibited higher accumulation of pp2c transcript than RH8812. However, lhcb gene was found to be down regulated during drought and its expression was present only in shoots. Seeds of both the genotypes were grown on MS medium with various levels of stress treatments using Mannitol and ABA. Seed germination was arrested at initial stage only and reduction in seed germination was significant among treatments and no seedling growth was observed in case of ABA treatment. Physiological parameters such as relative water content, osmotic potential, electrolyte leakage and chlorophyll fluorescence were also evaluated in stressed and control plants of both the genotypes and we found that physiological response was consistent with the changes in gene expression.