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首页> 外文期刊>Journal of Experimental Botany >Proanthocyanidin oxidation of Arabidopsis seeds is altered in mutant of the high-affinity nitrate transporter NRT2.7
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Proanthocyanidin oxidation of Arabidopsis seeds is altered in mutant of the high-affinity nitrate transporter NRT2.7

机译：高亲和力硝酸盐转运蛋白NRT2.7突变体中拟南芥种子的原花色素氧化被改变

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摘要

The seed-specific nitrate transporter AtNRT2.7 is involved in flavonoid accumulation as evidenced by the higher proanthocyanidin content in nrt2.7-2 mutant seeds. As TT10 laccase activity is not modified, the link between NRT2.7 and proanthocyanidin accumulation has yet to be discovered.NRT2.7 is a seed-specific high-affinity nitrate transporter controlling nitrate content in Arabidopsis mature seeds. The objective of this work was to analyse further the consequences of the nrt2.7 mutation for the seed metabolism. This work describes a new phenotype for the nrt2.7-2 mutant allele in the Wassilewskija accession, which exhibited a distinctive pale-brown seed coat that is usually associated with a defect in flavonoid oxidation. Indeed, this phenotype resembled those of tt10 mutant seeds defective in the laccase-like enzyme TT10/LAC15, which is involved in the oxidative polymerization of flavonoids such as the proantocyanidins (PAs) (i.e. epicatechin monomers and PA oligomers) and flavonol glycosides. nrt2.7-2 and tt10-2 mutant seeds displayed the same higher accumulation of PAs, but were partially distinct, since flavonol glycoside accumulation was not affected in the nrt2.7-2 seeds. Moreover, measurement of in situ laccase activity excluded a possibility of the nrt2.7-2 mutation affecting the TT10 enzymic activity at the early stage of seed development. Functional complementation of the nrt2.7-2 mutant by overexpression of a full-length NRT2.7 cDNA clearly demonstrated the link between the nrt2.7 mutation and the PA phenotype. However, the PA-related phenotype of nrt2.7-2 seeds was not strictly correlated to the nitrate content of seeds. No correlation was observed when nitrate was lowered in seeds due to limited nitrate nutrition of plants or to lower nitrate storage capacity in leaves of clca mutants deficient in the vacuolar anionic channel CLCa. All together, the results highlight a hitherto-unknown function of NRT2.7 in PA accumulation/oxidation.
机译：种子特异性硝酸盐转运蛋白AtNRT2.7参与类黄酮的积累，这可通过nrt2.7-2突变种子中原花青素含量更高来证明。由于TT10漆酶的活性没有改变，因此尚未发现NRT2.7和原花色素素积累之间的联系。NRT2.7是种子特异性的高亲和力硝酸盐转运蛋白，控制拟南芥成熟种子中的硝酸盐含量。这项工作的目的是进一步分析nrt2.7突变对种子代谢的影响。这项工作描述了Wassilewskija登录号中的nrt2.7-2突变等位基因的新表型，表现出独特的浅褐色种皮，通常与类黄酮氧化缺陷有关。确实，该表型类似于漆酶样酶TT10 / LAC15中有缺陷的tt10突变种子的表型，该酶参与类黄酮如原花色素（PAs）（表儿茶素单体和PA低聚物）和黄酮糖苷的氧化聚合反应。 nrt2.7-2和tt10-2突变体种子表现出相同的较高PA积累，但部分不同，因为在nrt2.7-2种子中黄酮醇苷的积累不受影响。此外，对原位漆酶活性的测量排除了在种子发育早期的nrt2.7-2突变影响TT10酶活性的可能性。通过全长NRT2.7 cDNA的过表达，nrt2.7-2突变体的功能互补清楚地证明了nrt2.7突变与PA表型之间的联系。但是，nrt2.7-2种子的PA相关表型与种子的硝酸盐含量并不严格相关。当由于植物有限的硝酸盐营养或由于液泡阴离子通道CLCa缺陷的clca突变体的叶片中硝酸盐储存能力降低而使种子中的硝酸盐降低时，没有观察到相关性。总之，这些结果突出了NRT2.7在PA积累/氧化中迄今未知的功能。

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