Post Graduate Department of Biotechnology, St. Xavier's College (Autonomous), 30, Mother Teresa Sarani, Kolkata, 700016, West Bengal, India.
Post Graduate Department of Biotechnology, St. Xavier's College (Autonomous), 30, Mother Teresa Sarani, Kolkata, 700016, West Bengal, India.
J Biotechnol. 2020 Dec 20;324:220-232. doi: 10.1016/j.jbiotec.2020.10.013. Epub 2020 Oct 14.
The objective of the present investigation was to understand the impact of exogenously applied melatonin on mitochondrial respiration and sugar metabolism in two contrasting rice cultivars, viz., Khitish (arsenic-susceptible) and Muktashri (arsenic-tolerant) under arsenic-stress. Melatonin effectively restored the level of organic acids like pyruvic acid, malic acid and more particularly citric acid by 33 % in Khitish which were lowered during arsenic-stress, whereas their levels were further elevated in Muktashri to provide energy for defence against arsenic-induced injury. Arsenic-exposure led to a significant inhibition in enzyme activities as well as corresponding transcript level of key respiratory enzymes, viz., pyruvate dehydrogenase, citrate synthase, isocitrate dehydrogenase, succinate dehydrogenase and malate dehydrogenase, intriguingly more prominently in case of Khitish. Conversely, melatonin supplementation, irrespective of cultivars, considerably improved the activity of the above enzymes and corresponding gene expressions during stress, indicating acceleration in the rate of Krebs cycle. Melatonin supplementation also stimulated the accumulation of total soluble sugars by 62 % and 25 %, reducing sugars by 50 % and 44 % and non-reducing sugars by 75 % and 14 % in Khitish and Muktashri respectively, concomitant with higher activities of acid invertase, sucrose synthase and sucrose phosphate synthase enzymes, along with the expression of corresponding genes. Enhanced starch accumulation via regulation of alpha amylase and starch phosphorylase activities and gene expression, by melatonin also contributed towards better stress tolerance. Overall, this work illustrated the efficacy of melatonin in the regulation of representative organic acids and enzymes of respiratory cycle along with starch and sugar metabolism in rice cultivars under arsenic toxicity.
本研究的目的是了解外源褪黑素对砷胁迫下两种不同水稻品种（Khitish（砷敏感）和 Muktashri（砷耐受））线粒体呼吸和糖代谢的影响。褪黑素有效地将有机酸（如丙酮酸、苹果酸，特别是柠檬酸）的水平恢复到 Khitish 中的 33%，而在砷胁迫下这些酸的水平降低，而在 Muktashri 中它们的水平进一步升高，为防御砷诱导的损伤提供能量。砷暴露导致酶活性以及关键呼吸酶（如丙酮酸脱氢酶、柠檬酸合酶、异柠檬酸脱氢酶、琥珀酸脱氢酶和苹果酸脱氢酶）的相应转录水平显著抑制，在 Khitish 中更为明显。相反，褪黑素补充剂，无论品种如何，在胁迫期间都能显著提高上述酶的活性和相应基因的表达，表明三羧酸循环的速率加快。褪黑素补充还刺激总可溶性糖的积累增加了 62%和 25%，还原糖减少了 50%和 44%，非还原糖减少了 75%和 14%，同时酸性转化酶、蔗糖合酶和蔗糖磷酸合酶的活性以及相应基因的表达也增加。通过调节α-淀粉酶和淀粉磷酸化酶的活性和基因表达，褪黑素也增强了淀粉的积累，有助于更好地耐受胁迫。总的来说，这项工作说明了褪黑素在调节砷毒性下水稻品种中代表性的有机酸和呼吸循环酶以及淀粉和糖代谢方面的功效。
