锰诱导甘蔗幼苗缺铁黄化及抗性机制研究

Aicd soils are the main problem soils in the world, while excess manganese is the main factor limiting crop development in acid soils. Breeding manganese-resistant crop cultivars by developing plant′s genetic potential is an economic and effective way to solve the problem in acid soils, while the elucidation of the mechanisms for manganese toxicity and resistance in plants is the precondition to breed manganese-resistant crop cultivars. The sugarcane production on acid soils in the south of China have been suffering from serious chlorsis problem, which has threatened country's sugar-industry safe seriously. Although our primary study results have revealed that the chlorsis was mainly resulted from excess manganese in the soils, correspond mechanisms have remain unclear. To elucidate the mechanisms for manganese tocixity and resistance in sugarcane, studies are carried out including: (1) iron-deficiency induced secretion of phytosiderophore and utilization of sparingly soluble iron, and their impacts on excess-manganese resistance in sugarcane seedlings；（2）the effect of excess manganese on plant iron-ultilization, the regulation of both seedlings chloresis, and the activity and homeostasis of iron by aniti-superoxidation system, iron redox, NO signaling and ferritin in sugarcane; (3) excess manganese effects on the synthesis and degradation of chlorophyll, and plant resistance to this effects. These studies have very important consequences for breeding manganese-resistant crop cultivars, solving the problem of sugarcane chlorsis on acid soils, and would be facilitate for making clear the nature of iron-manganese antagonistic effect in plants

酸性土壤是世界上主要的问题土壤，而锰毒是酸性土壤上作物生长的主要限制因子。挖掘植物遗传潜力培育耐锰作物新品种是克服锰毒害问题的经济有效途径，而阐明植物锰毒及抗性机制是利用现代生物技术培养新品种的前提。近年来南方酸性土壤上的甘蔗出现严重幼苗缺铁黄化问题，对我国蔗糖产业的威胁巨大。我们前期掌握的研究证据表明，过多的锰是导致酸性土壤上甘蔗幼苗缺铁黄化的主要因素，然而相关的机制尚不清楚。为揭示锰诱导甘蔗缺铁黄化及抗性的机制，本项目拟研究：（1）缺铁诱导甘蔗麦根酸类物质的分泌、难溶性铁吸收及其对甘蔗锰抗性的影响；（2）锰对甘蔗幼苗铁利用的影响以及锰胁迫下抗氧化系统、铁还原、一氧化氮信号、铁蛋白对甘蔗铁动态平衡、铁活性及幼苗黄化的调控；（3）过多的锰对甘蔗幼苗叶绿素合成与分解的影响及甘蔗的抗性。本研究对于抗锰毒甘蔗新品种培育、酸性土壤上甘蔗缺铁黄化问题的解决有重大意义并有助于揭示植物铁锰互作的本质。

酸性土壤是世界上主要的问题土壤，而锰毒是酸性土壤上作物生长的主要限制因子。挖掘植物遗传潜力培育耐锰作物新品种是克服锰毒害问题的经济有效途径，而阐明植物锰毒及抗性机制是利用现代生物技术培养新品种的前提。近年来南方酸性土壤上的甘蔗出现严重幼苗缺铁黄化问题，对我国蔗糖产业的威胁巨大。我们前期掌握的研究证据表明，过多的锰是导致酸性土壤上甘蔗幼苗缺铁黄化的主要因素，然而相关的机制尚不清楚。为揭示锰诱导甘蔗缺铁黄化及抗性的机制，本项目开展了麦根酸类物质的分泌与甘蔗锰抗性的关系、锰对甘蔗幼苗铁利用、叶绿素代谢的影响及相关机制的研究。研究确认了锰是引起的甘蔗幼苗黄化病的主因、危害程度并揭示了其田间发病规律，从世界各地近百个品种（系）中筛选获得锰毒抗性或难溶性铁吸收能力存在明显基因型差异的品种。研究发现，锰胁迫下甘蔗根系对难溶性铁的吸收和根尖高铁还原酶活性显著受阻且黄化感性品种收到的影响更显著，但是甘蔗根系麦根酸的分泌不因锰胁迫而变化；相对于铁吸收的影响，铁在组织的的活化受锰胁迫的抑制更显著，叶片中铁的钝化是导致甘蔗在锰胁迫环境下幼叶缺铁黄化的关键，而叶片中高铁还原是调控铁活性的重要途径；铁的钝化也与铁向幼叶转运受阻、尼克酰胺和柠檬酸等铁螯合剂减少、细胞壁铁固定有关；细胞壁果胶和半纤维素I是过多锰的主要结合位点，在甘蔗抵御锰毒方面也起到关键作用，抗性品种细胞壁及其果胶组分有更强的锰结合能力且因锰胁迫而强化；锰处理后叶绿素合成前体物ALA、PBG及叶绿素含量均显著降低，而叶面喷施ALA后锰引起的黄化症状减轻。另一方面，锰诱导甘蔗幼苗膜脂氧化，导致MDA积累、膜透性加大。可见，锰胁迫下铁的钝化、铁的细胞壁固持及叶绿素合成受阻可导致甘蔗幼叶缺铁黄化而叶片中铁活化和细胞壁固持锰是甘蔗重要的耐锰机制。本研究对于抗锰毒甘蔗新品种培育、酸性土壤上甘蔗缺铁黄化问题的解决有重大意义并有助于揭示植物铁锰互作的本质。