Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America.
PLoS Genet. 2011 Jun;7(6):e1002069. doi: 10.1371/journal.pgen.1002069. Epub 2011 Jun 9.
The molecular nature of biological variation is not well understood. Indeed, many questions persist regarding the types of molecular changes and the classes of genes that underlie morphological variation within and among species. Here we have taken a candidate gene approach based on previous mapping results to identify the gene and ultimately a polymorphism that underlies a trichome density QTL in Arabidopsis thaliana. Our results show that natural allelic variation in the transcription factor ATMYC1 alters trichome density in A. thaliana; this is the first reported function for ATMYC1. Using site-directed mutagenesis and yeast two-hybrid experiments, we demonstrate that a single amino acid replacement in ATMYC1, discovered in four ecotypes, eliminates known protein-protein interactions in the trichome initiation pathway. Additionally, in a broad screen for molecular variation at ATMYC1, including 72 A. thaliana ecotypes, a high-frequency block of variation was detected that results in >10% amino acid replacement within one of the eight exons of the gene. This sequence variation harbors a strong signal of divergent selection but has no measurable effect on trichome density. Homologs of ATMYC1 are pleiotropic, however, so this block of variation may be the result of natural selection having acted on another trait, while maintaining the trichome density role of the gene. These results show that ATMYC1 is an important source of variation for epidermal traits in A. thaliana and indicate that the transcription factors that make up the TTG1 genetic pathway generally may be important sources of epidermal variation in plants.
生物变异的分子本质尚不清楚。事实上，许多问题仍然存在，例如分子变化的类型以及构成物种内和种间形态变异的基因类别。在这里，我们基于先前的图谱结果采用了候选基因方法，以鉴定出一种基因，并最终鉴定出一种导致拟南芥毛状体密度 QTL 的多态性。我们的结果表明，转录因子 ATMYC1 的自然等位基因变异改变了拟南芥的毛状体密度；这是首次报道 ATMYC1 的功能。通过定点突变和酵母双杂交实验，我们证明了在四个生态型中发现的 ATMYC1 中的单个氨基酸替换消除了毛状体起始途径中已知的蛋白-蛋白相互作用。此外，在对包括 72 个拟南芥生态型在内的 ATMYC1 的广泛分子变异进行筛选时，发现了一个高频变异块，导致基因的八个外显子之一内的氨基酸替换率超过 10%。这种序列变异带有强烈的分歧选择信号，但对毛状体密度没有可测量的影响。然而，ATMYC1 的同源物是多效的，因此这种变异块可能是自然选择作用于另一个性状的结果，同时保持了基因的毛状体密度作用。这些结果表明，ATMYC1 是拟南芥表皮性状变异的重要来源，并表明构成 TTG1 遗传途径的转录因子通常可能是植物表皮变异的重要来源。
