Malate Synthesis and Secretion Mediated by a Manganese-Enhanced Malate Dehydrogenase Confers Superior Manganese Tolerance in Stylosanthes guianensis
Malate Synthesis and Secretion Mediated by a Manganese-Enhanced Malate Dehydrogenase Confers Superior Manganese Tolerance in Stylosanthes guianensis
复制标题
DOI：
10.1104/pp.114.251017
复制
发表时间：
2015-01-01
期刊：
影响因子：
7.4
通讯作者：
Liao, Hong
中科院分区：
文献类型：
--
作者：
Chen, Zhijian;Sun, Lili;Liao, Hong
锰的毒性是限制植物在酸性土壤上生长的主要限制因素。柱花草优良的耐锰性。已经得到了很好的证明，但其分子机制在很大程度上仍不清楚。在本研究中，柱花草具有较强的耐锰性，表现为较高的锰毒阈值。此外，对贵州省两个品种的耐锰性进行了遗传变异分析，结果表明，优良茎型比TPRC2001-1具有更高的耐锰性，表现为在过量锰下干重下降较少，并伴随着较低的体内锰浓度。有趣的是，锰刺激的苹果酸浓度和渗出速率的增加只在细茎品种中观察到。细茎根蛋白质组学分析表明，苹果酸脱氢酶1(SgMDH1)的积累响应于锰的毒害。Western-Blot和定量聚合酶链式反应分析表明，锰毒害只导致SgMDH1在细茎根中积累增加，而在TPRC2001-1中没有。SgMDH1介导的苹果酸合成的功能是通过体外生化分析SgMDH1对草酰乙酸酯的活性，以及在体内增加酵母(Saccharmyces Cerevisiae)、大豆(Glyine Max)毛状根和拟南芥(Arabiopsis Thaliana)中的苹果酸浓度来验证的。此外，SgMDH1的过表达提高了拟南芥对锰的耐性，并伴随着苹果酸分泌量的增加和植物体内锰浓度的降低，表明分泌的苹果酸可以缓解植物中的锰毒害。综上所述，我们得出结论：贵州岛的耐锰性是通过苹果酸的合成和分泌来协调内外解毒来实现的，这种解毒受SgMDH1在转录和蛋白质水平上的调控。
Manganese (Mn) toxicity is a major constraint limiting plant growth on acidic soils. Superior Mn tolerance in Stylosanthes spp. has been well documented, but its molecular mechanisms remain largely unknown. In this study, superior Mn tolerance in Stylosanthes guianensis was confirmed, as reflected by a high Mn toxicity threshold. Furthermore, genetic variation of Mn tolerance was evaluated using two S. guianensis genotypes, which revealed that the Fine-stem genotype had higher Mn tolerance than the TPRC2001-1 genotype, as exhibited through less reduction in dry weight under excess Mn, and accompanied by lower internal Mn concentrations. Interestingly, Mn-stimulated increases in malate concentrations and exudation rates were observed only in the Fine-stem genotype. Proteomic analysis of Fine-stem roots revealed that S. guianensis Malate Dehydrogenase1 (SgMDH1) accumulated in response to Mn toxicity. Western-blot and quantitative PCR analyses showed that Mn toxicity resulted in increased SgMDH1 accumulation only in Fine-stem roots, but not in TPRC2001-1. The function of SgMDH1-mediated malate synthesis was verified through in vitro biochemical analysis of SgMDH1 activities against oxaloacetate, as well as in vivo increased malate concentrations in yeast (Saccharomyces cerevisiae), soybean (Glycine max) hairy roots, and Arabidopsis (Arabidopsis thaliana) with SgMDH1 overexpression. Furthermore, SgMDH1 overexpression conferred Mn tolerance in Arabidopsis, which was accompanied by increased malate exudation and reduced plant Mn concentrations, suggesting that secreted malate could alleviate Mn toxicity in plants. Taken together, we conclude that the superior Mn tolerance of S. guianensis is achieved by coordination of internal and external Mn detoxification through malate synthesis and exudation, which is regulated by SgMDH1 at both transcription and protein levels.