Institute of Plant Science and Resources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama, Japan.
Theor Appl Genet. 2011 May;122(8):1561-76. doi: 10.1007/s00122-011-1555-2. Epub 2011 Feb 27.
The grain color of wheat affects not only the brightness of flour, but also tolerance to preharvest sprouting. Grain color is controlled by dominant R-1 genes located on the long arm of hexaploid wheat chromosomes 3A, 3B, and 3D (R-A1, R-B1, and R-D1, respectively). The red pigment of the grain coat is composed of catechin and proanthocyanidin (PA), which are synthesized via the flavonoid biosynthetic pathway. We isolated the Tamyb10-A1, Tamyb10-B1, and Tamyb10-D1 genes, located on chromosomes 3A, 3B, and 3D, respectively. These genes encode R2R3-type MYB domain proteins, similar to TT2 of Arabidopsis, which controls PA synthesis in testa. In recessive R-A1 lines, two types of Tamyb10-A1 genes: (1) deletion of the first half of the R2-repeat of the MYB region and (2) insertion of a 2.2-kb transposon belonging to the hAT family. The Tamyb10-B1 genes of recessive R-B1 lines had 19-bp deletion, which caused a frame shift in the middle part of the open reading frame. With a transient assay using wheat coleoptiles, we revealed that the Tamyb10 gene in the dominant R-1 allele activated the flavonoid biosynthetic genes. We developed PCR-based markers to detect the dominant/recessive alleles of R-A1, R-B1, and R-D1. These markers proved to be correlated to known R-1 genotypes of 33 varieties except for a mutant with a single nucleotide substitution. Furthermore, double-haploid (DH) lines derived from the cross between red- and white-grained lines were found to necessarily carry functional Tamyb10 gene(s). Thus, PCR-based markers for Tamyb10 genes are very useful to detect R-1 alleles.
小麦的粒色不仅影响面粉的亮度，还影响其抗穗发芽能力。粒色由位于六倍体小麦染色体 3A、3B 和 3D 长臂上的显性 R-1 基因控制（分别为 R-A1、R-B1 和 R-D1）。粒皮的红色素由儿茶素和原花青素（PA）组成，它们通过类黄酮生物合成途径合成。我们分离了位于 3A、3B 和 3D 染色体上的 Tamyb10-A1、Tamyb10-B1 和 Tamyb10-D1 基因。这些基因编码 R2R3 型 MYB 结构域蛋白，类似于控制种皮中 PA 合成的拟南芥 TT2。在隐性 R-A1 系中，有两种类型的 Tamyb10-A1 基因：（1）缺失 MYB 区 R2 重复的前半部分，（2）插入属于 hAT 家族的 2.2kb 转座子。隐性 R-B1 系的 Tamyb10-B1 基因缺失了 19bp，导致开放阅读框的中部发生移码。通过对小麦幼茎的瞬时测定，我们揭示了显性 R-1 等位基因中的 Tamyb10 基因激活了类黄酮生物合成基因。我们开发了基于 PCR 的标记来检测 R-A1、R-B1 和 R-D1 的显性/隐性等位基因。这些标记与 33 个品种的已知 R-1 基因型相关，除了一个单核苷酸替换的突变体外。此外，来自红粒和白粒杂交的双单倍体（DH）系必然携带功能性 Tamyb10 基因。因此，基于 PCR 的 Tamyb10 基因标记非常有助于检测 R-1 等位基因。
