Percy J D, Philip R, Vodkin L O
Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana 61801, USA.
Plant Mol Biol. 1999 Jul;40(4):603-13. doi: 10.1023/a:1006221115522.
The pigmented seed coats of several soybean (Glycine max (L.) Merr.) plant introductions and isolines have unusual defects that result in cracking of the mature seed coat exposing the endosperm and cotyledons. It has previously been shown that the T (tawny) locus that controls the color of trichomes on stems and leaves also has an effect on both the structure and pigmentation of the seed coat. Distribution of pigmentation on the seed coat is controlled by alleles of the I (inhibitor) locus. It was also found that total seed coat proteins were difficult to extract from pigmented seed coats with i T genotypes because they have procyanidins that exhibit tannin properties. We report that the inclusion of poly-L-proline in the extraction buffer out-competes proteins for binding to procyanidins. Once this problem was solved, we examined expression of the proline-rich cell wall proteins PRP1 and PRP2 in pigmented genotypes with the dominant T allele. We found that both homozygous i T and i t genotypes have reduced soluble PRP1 levels. The epistatic interaction of the double recessive genotype at both loci is necessary to produce the pigmented, defective seed coat phenotype characteristic of seed coats with the double recessive i and t alleles. This implies a novel effect of an enzyme in the flavonoid pathway on seed coat structure in addition to its effect on flavonoids, anthocyanidins, and proanthocyanidins. No soluble PRP1 polypeptides were detectable in pigmented seed coats (i T genotypes) of isolines that also display a net-like pattern of seed coat cracking, known as the Net defect. PRP2 was also absent in one of the these lines. However, both PRP1 and PRP2 cytoplasmic mRNAs were found in the Net-defective seed coats. Together with in vitro translation studies, these results suggest that the absence of soluble PRP polypeptides in the defective Net lines is post-translational and could be due to a more rapid or premature insolubilization of PRP polypeptides within the cell wall matrix.
几种大豆（Glycine max (L.) Merr.）引进品种和近等基因系的种皮带有色素，存在异常缺陷，导致成熟种皮开裂，胚乳和子叶外露。此前研究表明，控制茎和叶上毛状体颜色的T（黄褐色）基因座对种皮的结构和色素沉着也有影响。种皮上色素沉着的分布受I（抑制剂）基因座等位基因的控制。还发现，具有iT基因型的有色种皮难以提取总种皮蛋白，因为它们含有具有单宁特性的原花青素。我们报告称，在提取缓冲液中加入聚-L-脯氨酸可以与蛋白质竞争，使其不与原花青素结合。解决这个问题后，我们研究了具有显性T等位基因的有色基因型中富含脯氨酸的细胞壁蛋白PRP1和PRP2的表达。我们发现，纯合的iT和it基因型的可溶性PRP1水平均降低。两个基因座的双隐性基因型的上位相互作用对于产生具有双隐性i和t等位基因的种皮特有的有色、有缺陷种皮表型是必要的。这意味着类黄酮途径中的一种酶除了对类黄酮、花青素和原花青素有影响外，对种皮结构还有一种新的作用。在也表现出种皮开裂网状模式（即网状缺陷）的近等基因系的有色种皮（iT基因型）中，未检测到可溶性PRP1多肽。在这些品系中的一个中也没有PRP2。然而，在有网状缺陷的种皮中发现了PRP1和PRP2的细胞质mRNA。结合体外翻译研究，这些结果表明，有缺陷的网状品系中可溶性PRP多肽的缺失是翻译后发生的，可能是由于细胞壁基质内PRP多肽更快或过早地不溶解。
