Due to its immense capability to concentrate in rice grain and ultimately in food chain, cadmium (Cd) has become the cause of an elevated concern among agriculturists, scientists and the environmental activists. Symbiotic association of Piriformospora indica (P. indica) has been characterized as a potential aid in combating heavy metal stress in plants for sustainable crop production but our scant knowledge regarding ameliorative tendency of P. indica against Cd, specifically in rice, necessitates an in-depth investigation. This study aimed at elaborating the underlying mechanisms involved in P. indica-mediated tolerance against Cd stress in two rice genotypes, IR8 and ZX1H, varying in Cd accumulation pattern. Either colonized or un-inoculated with P. indica, seedlings of both genotypes were subjected to Cd stress. The results showed that P. indica colonization significantly supported plant biomass, photosynthetic attributes and chlorophyll contents in Cd stressed plants. P. indica colonization sustained chloroplast integrity and reduced Cd translocation (46% and 64%), significantly lowering malondialdehyde (MDA) content (11.3% and 50.4%) compared to uninoculated roots under Cd stress in IR8 and ZX1H, respectively. A genotypic difference was evident when a 2-fold enhancement in root peroxidase (POD) activity was recorded in P. indica colonized IR8 plants as compared to ZX1H. The root proteomic analysis was performed using isobaric tags for relative and absolute quantification (iTRAQ) and the results showed that P. indica alleviates Cd stress in rice via down-regulation of key glycolysis cycle enzymes in a bid to reduce energy consumption by the plants and possibly re-directing it to Cd defense response pathways; and up-regulation of glutamine synthetase, a key enzyme in the L-Arg-dependent pathway for nitric oxide (NO) production, which acts as a stress signaling molecule, thus conferring tolerance by reduction of NO-mediated modification of essential proteins in response to Cd stress. Conclusively, both the tested genotypes benefited from P. indica symbiosis at varying levels by an enhanced detoxification capacity and signaling efficiency in response to stress. Hence, a step forward towards the employment of an environmentally sound and self-renewing approach holding the hope for a healthy future.

由于其在大米中并最终在食物链中的巨大能力，镉 (Cd) 已成为农业学家、科学家和环保活动家高度关注的原因。Piriformospora indica ( P. indica ) 的共生关联已被表征为对抗植物中的重金属胁迫以实现可持续作物生产的潜在帮助，但我们对P. indica对 Cd 的改善趋势知之甚少，特别是在水稻中，需要在深入调查。本研究旨在阐明P. indica 中涉及的潜在机制介导的两种水稻基因型 IR8 和 ZX1H 对 Cd 胁迫的耐受性，在 Cd 积累模式上有所不同。无论是定殖还是未接种P. indica，两种基因型的幼苗都受到 Cd 胁迫。结果表明，籼稻定植显着支持镉胁迫植物的植物生物量、光合属性和叶绿素含量。与 IR8 和 ZX1H 中镉胁迫下未接种的根相比，籼稻的定植维持了叶绿体完整性并减少了 Cd 易位（46% 和 64%），显着降低了丙二醛 (MDA) 含量（11.3% 和 50.4%）。当在P. indica 中记录根过氧化物酶 (POD) 活性增加 2 倍时，基因型差异很明显与 ZX1H 相比，定居的 IR8 植物。使用同量异位标记进行相对和绝对定量 (iTRAQ) 进行根蛋白质组学分析，结果表明P. indica通过下调关键糖酵解循环酶来减轻水稻的 Cd 胁迫，以减少植物的能量消耗和可能将其重定向到 Cd 防御反应途径；和谷氨酰胺合成酶的上调，这是L -Arg 依赖途径中产生一氧化氮 (NO)的关键酶，作为应激信号分子，因此通过减少 NO 介导的必需蛋白质的修饰来赋予耐受性到 Cd 应力。最后，两种测试的基因型都受益于P. indica通过增强解毒能力和响应压力的信号效率，在不同水平上共生。因此，朝着采用对环境无害且自我更新的方法迈进了一步，为健康的未来带来了希望。