Abstract：
The manuscript revealed the ameliorative effects of exogenous melatonin in two distinct reproductive stages, i.e., developing grains (20 days after pollination) and matured grains (40 days after pollination) in two contrasting indica rice genotypes, viz., Khitish (arsenic-susceptible) and Muktashri (arsenic-tolerant), irrigated with arsenic-contaminated water throughout their life-cycle. Melatonin administration improved yield-related parameters like rachis length, primary and secondary branch length, number of grains per panicle, number of filled and empty grains per panicle, grain length and breadth and 1000-grain per weight. Expression of GW2, which negatively regulates grain development, was suppressed, along with concomitant induction of positive regulators like GIF1, DEP1 and SPL14 in both Khitish and Muktashri. Melatonin lowered arsenic bioaccumulation in grains and tissue biomass, more effectively in Khitish. Unregulated production of reactive oxygen species, leading to cellular necrosis caused by arsenic, was reversed in presence of melatonin. Endogenous melatonin level was stimulated due to up-regulation of the key biosynthetic genes, SNAT and ASMT. Melatonin enhanced the production of diverse antioxidants like anthocyanins, flavonoids, total phenolics and ascorbic acid and also heightened the production of thiol-metabolites (cysteine, reduced glutathione, non-protein thiols and phytochelatin), ensuring effective chelation and arsenic detoxification. Altogether, our observation, supported by principal component analysis, proved that melatonin re-programs the antioxidative metabolome to enhance plant resilience against arsenic stress to mitigate oxidative damages and reduce arsenic translocation from the soil to tissue biomass and edible grains.
摘要：
手稿揭示了外源性褪黑激素在两个不同的生殖阶段的改善作用，即，发育中的谷粒（授粉后20天）和成熟的谷粒（授粉后40天）在两个不同的印度水稻基因型，viz.,Khitish（对砷敏感）和Muktashri（耐砷），在整个生命周期中都用砷污染的水灌溉。褪黑激素的给药改善了产量相关的参数，例如轴长度，主要和次要分支长度，每穗的粒数，每穗填充和空粒的数量，谷物的长度和宽度以及每重量1000粒。负调控籽粒发育的GW2的表达,被压制，同时在Khitish和Muktashri中诱导了GIF1，DEP1和SPL14等正调节因子。褪黑素降低了谷物和组织生物量中砷的生物积累，在Khitish更有效。不受管制的活性氧的产生，导致砷引起的细胞坏死，在褪黑激素存在下逆转。内源性褪黑激素水平由于关键生物合成基因的上调而受到刺激，SNAT和ASMT。褪黑激素增强了多种抗氧化剂的产生，如花青素，黄酮类化合物，总酚类和抗坏血酸，也增加了硫醇代谢物的产生(半胱氨酸，还原型谷胱甘肽,非蛋白质硫醇和植物螯合素），确保有效的螯合和砷解毒。总之,我们的观察,在主成分分析的支持下，证明褪黑激素重新编程抗氧化代谢组以增强植物对砷胁迫的抵抗力，以减轻氧化损伤并减少砷从土壤到组织生物量和可食用谷物的转运。
