Abstract

The main aim of this manuscript was to demonstrate the reprogramming of nitrogen and GABA metabolism in the two rice cultivars (Khitish and MTU1010) in response to fluoride stress (25 mg L^?1) for 10 and 20 days. The seedlings were grown under 16/8 h light/dark photoperiodic cycle in a plant growth chamber. Fluoride stress significantly hampered growth and biomass of Khitish and MTU1010 after 10 days and 20 days of treatment, respectively. Fluoride stress reduced the level of total and soluble nitrogen, nitrate and nitrite, concomitant with inhibited activity of NR and NiR, along with corresponding gene expression level. In response to fluoride stress, the total amino acids were significantly enhanced in the seedlings, contributing towards better growth. Level of ammonium ions was also enhanced in the stressed seedlings, along with inhibited activity of GS and GOGAT, implying that the incorporation of ammonium ions into glutamine and glutamate via GS and GOGAT was hindered during fluoride stress. Expression level of GS and GOGAT was accordingly regulated in the seedlings of both the varieties. The endogenous GABA content was enhanced in both the cultivars along with the induced catalytic activity of GDH and GAD and their corresponding gene expression level. Our work clearly demonstrated that differential reprogramming of the metabolites and enzymes of nitrogen assimilation pathways was largely responsible for the differential pattern of adaptive strategies against fluoride stress in the two varieties, viz., Khitish and MTU1010, the former exhibiting resilience against long-term stress, whilst the latter showing greater susceptibility.

*Original full-text article online at: https://link.springer.com/article/10.1007/s00344-022-10780-5