Insight into the role of anthocyanin biosynthesis-related genes in Medicago truncatula mutants impaired in pigmentation in leaves
Insight into the role of anthocyanin biosynthesis-related genes in Medicago truncatula mutants impaired in pigmentation in leaves
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DOI：
10.1016/j.plaphy.2013.05.030
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发表时间：
2013-09-01
影响因子：
6.5
通讯作者：
Bernardi, Jamila
中科院分区：
文献类型：
--
作者：
Carletti, Giorgia;Lucini, Luigi;Bernardi, Jamila
黄酮类化合物是植物中最常见的抗氧化化合物。本研究从表型、代谢产物、基因结构和转录水平对蒺藜苜蓿的两个野生型和两个独立突变体进行了研究。黄酮类化合物的配置文件显示保守水平的二氢黄酮醇，leucoanthocyanidins和黄酮醇，而花青素，花青素和黄酮类化合物的水平较低的突变体（高达90%以下）与野生型相比。通过RT-PCR分析了编码花青素途径关键酶和转录因子的基因，发现参与花青素途径后期步骤的基因（二氢山奈酚还原酶2，UDP-葡萄糖：花青素3-O-葡萄糖基转移酶和谷胱甘肽S-转移酶）在两种突变体中表达不足。二氢山奈酚还原酶1在花色苷较少的突变体中下调了两倍，而UDP-葡萄糖：花色苷5-O-葡萄糖基转移酶仅在色素沉着较低的突变体中受到强烈抑制，这表明两种基因型的调节不同。共同的特点是类黄酮生物合成途径的第一个酶的表达速率没有改变。对于两个同源R2 R3 MYB基因，即MtMYBA和AN 2，也发现转录物积累的非常高的减少，这表明这些基因在叶中的花色素苷积累中起作用。通过核苷酸序列分析发现，突变体与野生型之间存在多个SNP位点，在MYB基因编码区和非编码区存在插入和缺失，这可能影响花青素的生物合成。此外，在M. 5号染色体上发现了一个由8个MYB基因组成的亚家族，该亚家族与MtMYBA具有高度同源性。蒺藜(c)2013年Elsevier Masson SAS。All rights reserved.
Flavonoids are the most common antioxidant compounds produced in plants. In this study, two wild types and two independent mutants of Medicago truncatula with altered anthocyanin content in leaves were characterized at the phenotype, metabolite profile, gene structure and transcript levels. Flavonoid profiles showed conserved levels of dihydroflavonols, leucoanthocyanidins and flavonols, while anthocyanidin, anthocyanin and isoflavone levels were lower in the mutants (up to 90% less) compared with the wild types. Genes encoding key enzymes of the anthocyanin pathway and transcriptional factors were analyzed by RT-PCR Genes involved in the later steps of the anthocyanin pathway (dihydrokaempferol reductase 2, UDP-glucose:anthocyanin 3-O-glucosyltransferase and glutathione S-transferase) were found under-expressed in both mutants. Dihydrokaempferol reductase 1 was downregulated two-fold in the anthocyanin-less mutant while the UDP-glucose:anthocyanin 5-O-glucosyltransferase was strongly repressed only in the mutant with low pigmentation, suggesting a different regulation in the two genotypes. The common feature was that the first enzymes of the flavonoid biosynthesis pathway were not altered in rate of expression. A very high reduction in transcript accumulation was also found for two homologous R2R3 MYB genes, namely MtMYBA and AN2, suggesting that these genes have a role in anthocyanin accumulation in leaves. More evidence was found on analyzing their nucleotide sequence: several SNPs, insertions and deletions in the coding and non-coding regions of both MYB genes were found between mutants and wild types that could influence anthocyanin biosynthesis. Moreover, a subfamily of eight MYB genes with a high homology to MtMYBA was discovered in tandem on chromosome 5 of M. truncatula. (c) 2013 Elsevier Masson SAS. All rights reserved.