Response of adenine and pyridine metabolism during germination and early seedling growth under arsenic stress in Brassic
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ORIGINAL PAPER
Response of adenine and pyridine metabolism during germination and early seedling growth under arsenic stress in Brassica juncea Sudhakar Srivastava • Jincy Joseph Akkarakaran Penna Suprasanna • Stanislaus Francis D’Souza
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Received: 18 June 2012 / Revised: 29 October 2012 / Accepted: 30 October 2012 / Published online: 11 November 2012 Ó Franciszek Go´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako´w 2012
Abstract Adenine and pyridine nucleotides play vital roles in virtually all aspects of plant growth. This study analyzed the response of adenine and pyridine metabolism during germination and early seedling growth (ESG) of Brassica juncea exposed to two doses of arsenate (AsV), 100 and 250 lM, having non-significant or significant inhibitory effects, respectively, on germination and ESG. The ratio of NAD/NADP and NAD/NADH showed no significant change in control and 100 lM AsV, but increased significantly at 250 lM AsV during initial 24 h and also at 7th day. The activity of enzymes of NAD metabolism, viz. NAD kinase, NADP phosphatase, nicotinamidase and poly(ADP-ribose) polymerases showed significant change mostly at 250 lM AsV. Further, significant decrease was observed in the ratio of ATP/ADP and in the activities of adenylate kinase and apyrase at 250 lM AsV at 7th day. External supply of ATP (1 mM) to 100 and 250 lM AsV significantly improved germination percentage and germination strength of the seeds as compared to AsV treatments alone. The study concludes that with the increase in concentration of AsV, the balance of NAD/NADP, NAD/NADH and ATP/ADP and the Communicated by J. van Staden.
Electronic supplementary material The online version of this article (doi:10.1007/s11738-012-1146-0) contains supplementary material, which is available to authorized users. S. Srivastava (&) J. J. Akkarakaran P. Suprasanna S. F. D’Souza Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, Maharashtra, India e-mail: [email protected] P. Suprasanna e-mail: [email protected]
activities of enzymes of adenine and pyridine metabolism were significantly altered and that these changes may be responsible for inhibitory effects of AsV on germination and ESG. Keywords Arsenic ATP Germination Nicotinamidase PARP Pyridine nucleotides
Introduction Arsenic (As) is a toxic metalloid whose exposure to plants disturbs nitrogen (Singh et al. 2009) and sugar (Jha and Dubey 2005; Choudhury et al. 2010) metabolism and induces oxidative stress reactions (Srivastava et al. 2011) leading to toxicity. However, with respect to toxicity, germination and early seedling growth (ESG) may play a determining role in tolerance at later stages of plant life. It is known that As exposure affects germination and seedling growth and that arsenite (AsIII) and arsenate (AsV) have differential effects (Abedin and Meharg 2002). However, the mechanism of toxicity at initial stages is still unknown. Srivastava et al. (2011) established that redox
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