GABA and nitric oxide reduce AsV toxicity in tomato and brinjal seedlings by regulating sulphur assimilation and proline metabolism

Abstract

Arsenate (AsV) is one of the most hazardous elements, and its increasing accumulation in plants is the major area of concern in present days. Therefore, an environmentally reliable approach is required to reduce the load of AsV into vegetables. In the current study, the potential role of gamma amino butyric acid (GABA; 10 µM) and sodium nitroprusside a donor of NO (SNP; 10 µM) in 21 days old seedlings of tomato and brinjal grown in Hoagland medium containing 25 µM of AsV was analysed by estimating physiological and biochemical attributes. AsV exposure reduced root and shoot length and dry mass by 18, 9 % and 15 % in tomato, and 23 and 10 %, and 27 % in brinjal seedlings, respectively. Additionally, AsV decreased leaf gas exchange parameters i.e. stomatal conductance, internal CO2 concentration, transpiration rate and subsequently photosynthetic rate. Although AsV stimulated sulphur assimilation and proline metabolism, but it raised the oxidative stress as evident by increased biomarkers; superoxide radicals (SOR), hydrogen peroxide (H2O2), lipid peroxidation (MDA), and protein oxidation in both the seedlings. The application of GABA and SNP significantly mitigated negative effects of AsV on both the vegetables. The results indicate that GABA was unable to reduce AsV stress in the presence of L-NAME (an endogenous NO biosynthetic inhibitor), but addition of SNP rescued the effect of L-NAME. Overall, the findings suggest that GABA and SNP effectively mitigate AsV stress however, the involvement of NO appears to be necessary for GABA to achieve this task efficiently in the studied vegetables. These results will help to design strategies for mitigating arsenate stress in vegetable crops.