A novel R3 MYB transcriptional repressor associated with the loss of floral pigmentation in Iochroma
A novel R3 MYB transcriptional repressor associated with the loss of floral pigmentation in Iochroma
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DOI：
10.1111/nph.14830
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发表时间：
2018-02-01
期刊：
影响因子：
9.4
通讯作者：
Smith, Stacey D.
中科院分区：
文献类型：
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作者：
Gates, Daniel J.;Olson, Bradley J. S. C.;Smith, Stacey D.
花色素的丧失是花色进化中最常见的转变之一，但这些变化的遗传基础仅在少数情况下得到阐明。本研究采用杂交研究、批量分离RNA测序、系统发育分析和功能测试来鉴定Iochroma oxense中负责向白色花转变的基因。loxense及其蓝花姊妹种，即I. cyaneum的研究表明，一个单一的基因座控制花的颜色差异，而白色等位基因导致色素几乎完全丧失。通过检查杂交后代表型库中的序列变异，我们发现一种新的R3 MYB转录因子的等位基因与花色变异密切相关。该基因，我们称之为MYBL 1，福尔斯属于一类MYB转录抑制子，因此，该基因的更高表达与多种花青素色素途径基因的下调相关。我们通过稳定转化烟草证实了MYBL 1的抑制功能。loxense与以前的研究中发现的不同，指出了实现花色强度固定转换的多种机制。
Losses of floral pigmentation represent one of the most common evolutionary transitions in flower color, yet the genetic basis for these changes has been elucidated in only a handful of cases.Here we used crossing studies, bulk-segregant RNA sequencing, phylogenetic analyses and functional tests to identify the gene(s) responsible for the transition to white flowers in Iochroma loxense.Crosses between I. loxense and its blue-flowered sister species, I. cyaneum, suggested that a single locus controls the flower color difference and that the white allele causes a nearly complete loss of pigmentation. Examining sequence variation across phenotypic pools from the crosses, we found that alleles at a novel R3 MYB transcription factor were tightly associated with flower color variation. This gene, which we term MYBL1, falls into a class of MYB transcriptional repressors and, accordingly, higher expression of this gene is associated with downregulation of multiple anthocyanin pigment pathway genes. We confirmed the repressive function of MYBL1 through stable transformation of Nicotiana.The mechanism underlying the evolution of white flowers in I. loxense differs from that uncovered in previous studies, pointing to multiple mechanisms for achieving fixed transitions in flower color intensity.