Effects of salt stress on physio-biochemical characters and gene expressions in halophyte grass Leptochloa fusca (L.) Kunth

Kallar grass (Leptochloa fusca) is a perennial C4 halophytic species with high salt tolerant. The present research was made to investigate the physio-biochemical characters and transcriptional changes of L. fusca under varying salinity levels (0-600mM NaCl). The Na+ level in shoots and roots increased significantly, whereas the K+ content was maintained high in 300mM NaCl and then declined with increasing salinity in both tissues. The content of proline in seedlings exposed to extreme salinity level was 15.5-fold higher than control. Photosynthetic pigments, total soluble proteins, PAL activity, and total phenolic compounds in salt-stressed plants increased gradually up to 450mM and declined at 600mM NaCl. High salt concentration led to oxidative stress that was manifested by increased MDA level. To tackle with oxidative damages, L. fusca enhanced the activity of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Moreover, under NaCl stress, the mRNA levels of SOS1, PM H+-ATPase, and NHX1 were up-regulated in both tissues, but higher in roots than in shoots. Our results demonstrate that L. fusca could use an osmotic adjustment, antioxidant defense system,and regulating the ion homeostasis as the most effective salt tolerance mechanisms for better plant growth under saline conditions.