Identification and biochemical characterization of mutants in the proanthocyanidin pathway in Arabidopsis
Identification and biochemical characterization of mutants in the proanthocyanidin pathway in Arabidopsis
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DOI：
10.1104/pp.006189
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发表时间：
2002-10-01
期刊：
影响因子：
7.4
通讯作者：
Ashton, AR
中科院分区：
文献类型：
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作者：
Abrahams, S;Tanner, GJ;Ashton, AR
原花青素(PA)，或缩合单宁，是一种聚合的黄醇，在各种植物的许多组织中积累。在拟南芥中，我们发现PA前体(用OsO4组织化学检测到)从胚胎发育的两个末端细胞阶段开始在种皮的内皮细胞层积累。为了了解PA是如何形成的，我们对T-DNA标记的拟南芥品系的成熟种子库进行了筛选，以鉴定在PA合成方面存在缺陷的突变体，并发现了6个在PA合成方面存在缺陷的TDS(单宁缺乏种子)互补基团。这些基因座的突变会破坏内皮细胞层中PA的数量(tds1、tds2、tds3、tds5和tds6)或位置和数量(Tds4)。在野生型和突变体tds1、tds2、tds3和tds5(不产生PA)和tds6(占野生型PA的6%)和tds4(野生型PA的2%)中发现了PA中间体表儿茶素，而tds4(野生型PA的2%)产生了一种未知的二甲氨基肉桂醛反应化合物，这表明突变可能作用于亮氨酸花青素还原酶以外的基因，这是专门合成PA的第一个酶还原步骤。另外两个突变体被鉴定出来，一个是tt7的等位基因，它有PA沉积的斑点模式，只产生野生型PA水平的8%，是丙精氨酸和tt8的等位基因，不产生PA。在突变体tds4和tt7-3的种子中观察到PA沉积的斑点模式是由于PA在细胞中的组成和分布发生了变化。我们的突变筛选并不是详尽的，它表明成功积累PA需要许多基因的合作。
Proanthocyanidin (PA), or condensed tannin, is a polymeric flavanol that accumulates in a number of tissues in a wide variety of plants. In Arabidopsis, we found that PA precursors (detected histochemically using OsO4) accumulate in the endothelial cell layer of the seed coat from the two-terminal cell stage of embryo development onwards. To understand how PA is made, we screened mature seed pools of T-DNA-tagged Arabidopsis lines to identify mutants defective in the synthesis of PA and found six tds (tannin-deficient seed) complementation groups defective in PA synthesis. Mutations in these loci disrupt the amount (tds1 tds2 tds3, tds5, and tds6) or location and amount of PA (tds4) in the endothelial cell layer. The PA intermediate epicatechin has been identified in wild type and mutants tds1, tds2, tds3, and tds5 (which do not produce PA) and tds6 (6% of wild-type PA) whereas tds4 (2% of wild-type PA) produces an unidentified dimethylaminocinnamaldehyde-reacting compound, indicating that the mutations may be acting on genes beyond leucoanthocyanidin reductase, the first enzymatic reduction step dedicated to PA synthesis. Two other mutants were identified, an allele of tt7, which has a spotted pattern of PA deposition and produces only 8% of the wild-type level of type PA as propelargonidin and an allele of tt8 producing no PA. Spotted patterns of PA deposition observed in seed of mutants tds4 and tt7-3 result from altered PA composition and distribution in the cell. Our mutant screen, which was not exhaustive, suggests that the cooperation of many genes is required for successful PA accumulation.