J Exp Bot:中科院武汉植物园韩月彭研究组揭示桃树同开红白“双色

9月10日JouRNAl Experimental Botany发表中国科学院武汉植物园韩月彭研究组对桃树开红白“双色花”机理的最新成果，研究结果不仅促进了人们对果树芽变机理的认识，而且也为植物色泽性状遗传改良以及突变创制提供了新的技术与思路。

桃花着色源于花青素的积累，桃花杂色表型(同树齐开红花、白花，详见下图)具有重要的观赏价值。武汉植物园程钧博士在韩月彭研究员指导下，克隆了控制桃花杂色表型基因Riant，该基因编码一种花青素转运体，负责将花青素向液泡中转运。在白花枝条中，该基因编码区由于两个碱基的插入引起了移码突变，基因功能丧失成了假基因(命名为riant)，导致花青素无法向液泡中转运、积累，花瓣呈白色。有趣的是，研究发现riant基因上述突变位点易发生几个碱基的缺失或插入，形成大家熟悉的芽变，且该芽变频率很高，其中红花芽变归结于下列两种变异：riant基因缺失2个碱基或插入1个碱基，以第一种变异最为常见。这两种变异都会导致基因编码框恢复正常，能够行使正常功能，使得花青素能够向液泡中转运、积累，花瓣呈红色。此外，riant基因突变可在花芽不同发育阶段发生，并在表皮细胞(L1层)及其下层(L2)形成不同嵌合体，导致桃花呈现多种杂色表型。

原文链接：

A small indel mutation in an anthocyanin transporter causes variegated colouration of peach flowers

原文摘要：

The ornamental peach cultivar ‘Hongbaihuatao (HBH)’ can simultaneously bear pink, red, and variegated flowers on a single tree. Anthocyanin content in pink flowers is extremely low, being only 10% that of a red flower. Surprisingly, the expression of anthocyanin structural and potential regulatory genes in white flowers was not significantly lower than that in both pink and red flowers. However, proteomic analysis revealed a GST encoded by a gene—regulator involved in anthocyanin transport (Riant)—which is expressed in the red flower, but almost undetectable in the variegated flower. The Riant gene contains an insertion-deletion (indel) polymorphism in exon 3. In white flowers, the Riant gene is interrupted by a 2-bp insertion in the last exon, which causes a frameshift and a premature stop codon. In contrast, both pink and red flowers that arise from bud sports are heterozygous for the Riant locus, with one functional allele due to the 2-bp deletion or a novel 1-bp insertion. Southern blot analysis indicated that the Riant gene occurs in a single copy in the peach genome and it is not interrupted by a transposon. The function of theRiant gene was confirmed by its ectopic expression in the Arabidopsis tt19mutant, where it complements the anthocyanin phenotype, but not the proanthocyanidin pigmentation in seed coat. Collectively,these results indicate that a small indel mutation in the Riant gene, which is not the result of a transposon insertion or excision, causes variegated colouration of peach flowers.

doi: 10.1093/jxb/erv419

作者：韩月彭