EXPRESSION ANALYSIS OF SERINE BIOSYNTHESIS PATHWAY GENES UNDER VARIOUS ABIOTIC STRESS IN Brassica juncea (L.) Czern.

Serine plays an important role in plant’s signaling, development and metabolism. Serine is synthesized by three different pathways, namely the phosphorylated pathway, the glycolate pathway, and the glycerate pathway. The presence of three different pathways for serine production has complexed our understanding of this non-essential amino acid. To identify which pathway is more important than the other, the expression of one key gene from each of the three pathways, i.e., phosphoserine phosphatase of phosphorylated pathway, Ser hydroxymethyl-transferase of glycolate pathway and glycerate dehydrogenase of glycerate pathway, was analyzed using semi quantitative RT-PCR. Expression of the genes was studied under different abiotic stress, which include salinity, drought, high and low temperature in 7 d old seedlings of Brassica juncea. The expression of above three genes was also studied in roots and shoots for understanding the tissue specific expression. It was seen that under different abiotic stress genes were expressed in both roots and shoots. To confirm whether the genes are light or dark regulated, expression of each gene was observed under dark and light conditions. Phosphoserine phosphatase gene of the phosphorylated pathway was found to be expressed both in light as well as dark. Hence, phosphorylated pathway was concluded to be more active under abiotic stress compared to the other two pathways.