Physiological and gene expression responses involved in teak (Tectona grandis L.) seedlings exposed to osmotic and salt stressors

Abstract

Teak (Tectona grandis L.) is a forest tree having 2n = 2x = 36 diploid chromosomes. Plants are continually subjected to variety of abiotic stresses due to climate change, which alter their physiological processes and gene expression. The current study sought to examine the physiological and differential gene expression of teak seedlings exposed to abiotic stresses (150mM NaCl and 15% PEG-6000). Chlorophyll content, membrane stability index and relative water content were measured at 0, 2, 7 and 12days after treatment. These parameters were initially numerically reduced, but they were significantly reduced during a longer period of treatment. Seedlings treated with 150mM NaCl displayed more harmful effect on the plant than other treatments. The results showed that variety of stresses significantly affect the physiology of seedlings because they cause membrane damage, ROS generation, chlorophyll degradation, and reduction in water absorption. The gene expression of treated and control seedlings was also evaluated at 12days after treatment. Ten stress-related genes were examined for their differential expression using RT-PCR under applied stress. The stress-treated seedlings' leaves showed an up-regulated expression of the genes MYB-3, HSP-1, BI-1 and CS-2. Up-regulation of the genes confirmed the protective function of these genes in plants under abiotic stress. However, gene expression was affected by treatments, the extent of stress and the species of plant. This study came to the conclusion that physiological parameters could be utilized as marker indices to assess a tree's capability to withstand stress at seedling stage. The up-regulated genes will be further investigated and utilized to validate stress tolerance and susceptible teak seedlings.