Effect of salt stress on expression of carotenoid pathway genes in tomato

Carotenoids, the naturally occurring isoprenoids form essential components of photosynthetic antenna and reaction centre complexes. Thus they play a significant role in absorption, dissipation and transfer of light energy for the process of photosynthesis. The effects of salt stress on carotenoid gene expression in tomato leaves were studied. For that tomato plants were subjected to different concentration of salt water. Morphological characters such as plant height, no. of fruits per plant, chlorophyll content and expression of four major carotenoid pathway genes such as phytoene synthase, phytoene desaturase, zeta carotene desaturase and lycopene beta cyclase were analysed. The quantitative expression analysis using real time PCR has shown a decrease in the expression of all the studied genes as the salt concentration increased. Among the different concentrations of NaCl used for the experiment, it was seen that 200 mM was most detrimental for the carotenoid gene expression. Lycopene beta cyclase, the enzyme that converts lycopene to beta carotene was seen to be highly affected compared to other genes studied showing a 1.87 fold inhibition in its expression at 200 mM NaCl.