Department of Plant Agriculture, University of Guelph, Guelph, ON, N1G 2W1, Canada.
Theor Appl Genet. 2020 Jun;133(6):1977-1994. doi: 10.1007/s00122-020-03571-7. Epub 2020 Feb 28.
The gene Phvul.010G130600 which codes for a MYB was shown to be tightly associated with seed coat darkening in Phaseolus vulgaris and a single nucleotide deletion in the allele in Wit-rood disrupts a transcription activation region that likely prevents its functioning in this non-darkening genotype. The beige and white background colors of the seed coats of conventional pinto and cranberry beans turn brown through a process known as postharvest darkening (PHD). Seed coat PHD is attributed to proanthocyanidin accumulation and its subsequent oxidation in the seed coat. The J gene is an uncharacterized classical genetic locus known to be responsible for PHD in common bean (P. vulgaris) and individuals that are homozygous for its recessive allele have a non-darkening (ND) seed coat phenotype. A previous study identified a major colorimetrically determined QTL for seed coat color on chromosome 10 that was associated with the ND trait. The objectives of this study were to identify a gene associated with seed coat postharvest darkening in common bean and understand its function in promoting seed coat darkening. Amplicon sequencing of 21 candidate genes underlying the QTL associated with the ND trait revealed a single nucleotide deletion (c.703delG) in the candidate gene Phvul.010G130600 in non-darkening recombinant inbred lines derived from crosses between ND 'Wit-rood boontje' and a regular darkening pinto genotype. In silico analysis indicated that Phvul.010G130600 encodes a protein with strong amino acid sequence identity (70%) with a R2R3-MYB-type transcription factor MtPAR, which has been shown to regulate proanthocyanidin biosynthesis in Medicago truncatula seed coat tissue. The deletion in the 'Wit-rood boontje' allele of Phvul.010G130600 likely causes a translational frame shift that disrupts the function of a transcriptional activation domain contained in the C-terminus of the R2R3-MYB. A gene-based dominant marker was developed for the dominant allele of Phvul.010G130600 which can be used for marker-assisted selection of ND beans.
基因 Phvul.010G130600 编码一个 MYB，与菜豆种子种皮变深密切相关，而 Wit-rood 等位基因中的一个单核苷酸缺失破坏了一个转录激活区，可能使其无法在这种非变深基因型中发挥作用。传统平托豆和蔓越莓豆的种皮的米色和白色背景颜色通过称为采后变深（PHD）的过程变成棕色。种皮 PHD 归因于原花青素的积累及其在种皮中的后续氧化。J 基因是一个未被描述的经典遗传位点，已知其负责普通菜豆（P. vulgaris）中的 PHD，纯合其隐性等位基因的个体具有非变深（ND）种皮表型。先前的研究确定了 10 号染色体上一个主要的基于比色的种皮颜色 QTL，与 ND 性状相关。本研究的目的是鉴定与普通菜豆种皮 PHD 相关的基因，并了解其促进种皮变深的功能。与 ND 性状相关的 QTL 下 21 个候选基因的扩增子测序显示，在 ND 'Wit-rood boontje' 和常规变深平托基因型之间杂交产生的非变深重组自交系中，候选基因 Phvul.010G130600 中存在单个核苷酸缺失（c.703delG）。计算机分析表明，Phvul.010G130600 编码的蛋白质与 R2R3-MYB 型转录因子 MtPAR 的氨基酸序列具有很强的同源性（70%），后者已被证明可调节 Medicago truncatula 种皮组织中原花青素的生物合成。'Wit-rood boontje' 等位基因中 Phvul.010G130600 的缺失可能导致翻译框架移位，破坏 R2R3-MYB 末端转录激活域的功能。为 Phvul.010G130600 的显性等位基因开发了一个基于基因的显性标记，可用于 ND 豆的标记辅助选择。
