Effect of GABA-Transaminase Inhibitor 3-MPA on Arabidopsis thaliana Grown Under Different Light Conditions

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Abstract
The adaptation of plants to biotic and abiotic stress depends on their abilities to sense their surroundings and to generate and transmit corresponding signals to different parts of their body that can evoke changes necessary for optimizing growth and defense. Light has been shown to be one of the key environmental factors that modulate the physiology of both plants and animals via the diverse photoreceptors found in them. Both plants and animals contain a large repertoire of intra- and intercellular signals molecules that include organic and inorganic. One such molecule is a neurotransmitter, γ-aminobutyric acid (GABA), a non-protein amino acid, that rapidly accumulates in plant tissues in response to biotic and abiotic stress and regulates plant growth. Lots of research has been done on GABA in plants for slightly more than half a century now: Its discovery in plant tissues was immediately followed by physiological and biochemical studies. Thereafter molecular-genetics era of cloning the genes encoding the GABA shunt enzymes and transporters, and recombinant expression and purification of the enzymes in vitro to elucidate their regulatory properties and substrate specificity was established. Recently the discovery of the first bona fide GABA target proteins in plants, the ALMTs suggest that GABA indeed could be one of the signaling molecules in plants. All this research did not address in detail the relationship between light and GABA. To better understand the role of GABA in relation to light we set up six light conditions to investigate the changes in the hypocotyl and root growth in Arabidopsis thaliana under different light conditions, including total light, total dark, light blocker, gradient light, shoot dark, shoot dark with blocker. We treated the seedlings with 3-MPA, a GABA inhibitor, using different concentrations grown under different light conditions between 24 to 96 h. Our results show that both the root and hypocotyl are modulated by GABA when grown under different light conditions. These results clearly suggest a link in the signaling pathway of GABA with photoreceptor signaling pathways.

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