GABA accretion reduces Lsi-1 and Lsi-2 gene expressions and modulates physiological responses in Oryza sativa to provide tolerance towards arsenic

Abstract

GABA counteracts wide range of stresses through regulation of GABA shunt pathway in plants. Although, GABA assisted tolerance against As toxicity in plants is still unexplored. We have examined GABA induced tolerance in rice seedlings with two exposure periods of GABA i.e., short term and long term. Results showed that accumulation of GABA reduced the expressions of Lsi-1 and Lsi-2 transporter genes, which ultimately decreased the accumulation of As in rice seedlings. The accumulation of GABA also modulated the gene expression of GABA shunt pathway and activity of antioxidant enzymes, which strongly induced the tolerance in plants. Antioxidant enzymes such as CAT, POD, GPX and SOD showed maximum alteration in activity with GABA accretion. In both exposure periods, long term accumulation of GABA was highly efficient to provide tolerance to plants against As(III), while higher level of GABA at short term was toxic. Tolerance responses of GABA towards As(III) was reflected by minimal changes in various physiological (WUE, A, gs, PhiPS2, qp, NPQ, ETR and Trmmol) and growth parameters with concomitant accumulation. Oxidative stress marker such as TBARS and H2O2 contents were reduced with GABA accumulation. These results suggested that GABA sturdily inhibits As accumulation and provides tolerance towards As(III).

The versatile GABA in plants

“…129 When rice seedlings grew under arsenic (As (III)) stress, GABA application induced GABA-shunt-related gene expression, activated the antioxidant enzyme system, and strongly inhibited As accumulation, thus conferring a tolerance to As (III) in the seedlings. 130 Interestingly, long-term accumulation of GABA is more highly efficient in inducing As (III) tolerance than higher GABA levels in the short term, which actually causes toxicity. 130 On the other hand, Cd stress seemingly reduces endogenous GABA content in duckweed, and under Cd stress, exogenous GABA enhanced rhizoid abscission, whereas Glu addition promotes rhizoid abscission.131 GAD genes are uniformly up-regulated in maize and rice roots by Cd stress, and the overexpression of ZmGAD1 and ZmGAD2 in Cd-sensitive yeast and tobacco leaves enhances Cd tolerance in the host cells.132 All of the aforementioned studies indicate that GABA content does not always increase in response to different metal stresses and may be more related to metal concentrations.…”

“… 130 Interestingly, long-term accumulation of GABA is more highly efficient in inducing As (III) tolerance than higher GABA levels in the short term, which actually causes toxicity. 130 On the other hand, Cd stress seemingly reduces endogenous GABA content in duckweed, and under Cd stress, exogenous GABA enhanced rhizoid abscission, whereas Glu addition promotes rhizoid abscission. 131 GAD genes are uniformly up-regulated in maize and rice roots by Cd stress, and the overexpression of ZmGAD1 and ZmGAD2 in Cd-sensitive yeast and tobacco leaves enhances Cd tolerance in the host cells.…”

Silicon in the Soil–Plant Continuum: Intricate Feedback Mechanisms within Ecosystems

“…Expression of the Lsi1 gene in rice is downregulated by Si supply, dehydration stress and abscisic acid (more strongly in Si-depleted plants), suggesting regulation of active Si uptake in response to changes in the transpiration stream and plant internal water balance [ 123 ]. Further studies have demonstrated how the expression of Lsi1 , Lsi2 and Lsi6 genes is regulated by plant hormones [ 124 ] and internal Si and metal concentrations [ 125 , 126 ].…”

Physiological and Biochemical Characterization of the GABA Shunt Pathway in Pea (Pisum sativum L.) Seedlings under Drought Stress

“…GABA is a four-carbon non-protein amino acid that increases in plant tissues under stress [29]. The GABA shunt has a functional role in biotic and abiotic stress in plants through the improvement in the antioxidant activity to restrict ROS species production, plant cell signaling, and metabolism under stress [29,30]. The GABA shunt pathway is composed of three enzymatic reactions.…”