Evolution of floral organ reduction

我们的目标是了解不同物种如何进化出不同的物理特征。开花植物是地球上所有植物类群中物种数量和多样性最多的植物，花瓣通过吸引不同的传粉媒介在产生这种多样性方面发挥了关键作用。许多植物也可以自己授粉，这对入侵新栖息地的杂草（如毛苦菜）是有利的。这种向自花授粉的转变可能与花瓣的丧失有关，然而，决定花瓣数量的遗传机制以及它们在进化过程中如何变化，人们知之甚少，因此是我们研究的重点。我们的研究旨在了解两种芥菜物种，模式生物芥蓝（拟南芥）和毛苦菜（Cardamine hirsuta）之间花瓣数量变化的遗传变化。这些物种关系密切，易于在实验室中进行研究，因此遗传和转基因实验可以用来确定使这两个物种看起来彼此不同的机制。泰利菜有典型的芥菜花，有四个花瓣，而多毛苦菜的不同之处在于花瓣较少。我们知道毛苦菜基因组的一个区域控制着这个物种在花瓣数量上观察到的大量变异。我们还知道，一个控制花瓣发育的重要基因“绿叶”（LEAFY）位于这个基因组区域。为了确定毛状苦菜花瓣数量的抑制基因，我们通过诱变诱导基因组变异，并鉴定出将毛状苦菜花瓣数量转化为蓝鳍苦菜花瓣数量的突变体。识别这些植物中的突变基因将告诉我们哪些基因在毛苦菜中起减少花瓣数量的作用，而在蓝菜中不起作用。LEAFY调节花瓣发育的一种方式是通过打开APETALA1基因的表达。在长尾菜中，而不是在多毛苦菜中，其他的调节因子也会开启这个基因。我们想知道这种基因调控的差异是否在这两个物种看起来不同的过程中起了作用。在这里，我们将确定是LEAFY基因还是不同的基因控制了在多毛苦菜种群中观察到的变异。我们还将确定只在毛状苦菜中起作用以减少花瓣数量的基因。在进化过程中，许多产生不同外观物种的遗传变化是由于基因调节方式的变化，我们将测试这两种芥菜的APETALA1基因是否适用。因此，毛腥菜和长尾腥菜之间花瓣数量的物种特异性差异，以及世界各地毛腥菜种群之间花瓣数量的自然变异，为追踪从基因调控的特定变化到自然界形态改变的进化提供了一个令人兴奋的实验平台。另一种被称为芸苔属的芥菜因含有比任何其他植物属更多的重要农业和园艺作物而引人注目。因此，了解芥菜多样性的遗传基础是培育21世纪作物的重要组成部分。

We aim to understand how different species evolve different physical features. Flowering plants have the greatest species number and diversity of any plant group on earth and petals played a critical role in generating this diversity by attracting different pollinators. Many plants can also pollinate themselves and this can be advantageous for weeds like hairy bittercress that invade new habitats. This transition to self-pollination can be associated with petal loss, however, the genetic mechanisms that determine petal number, and how these have varied during evolution, are poorly understood and are hence the focus of our research. Our research aims to understand the genetic changes that underlie changes in petal number between two mustard species, the model organism thale cress (Arabidopsis thaliana) and hairy bittercress (Cardamine hirsuta). These species are closely related and easy to work with in the lab, so genetic and transgenic experiments can be used to identify mechanisms that make these two species look different from each other. Thale cress has a typical mustard flower with four petals while hairy bittercress differs by having fewer petals. We know that one region of the hairy bittercress genome controls a large amount of the variation observed in petal number in this species. We also know that an important gene controlling petal development called LEAFY maps to this genomic region. In order to identify genes that repress petal number in hairy bittercress we induced variation in the genome by mutagenesis and identified mutants that convert hairy bittercress to thale cress petal number. Identifying the genes mutated in these plants will tell us which genes act to reduce petal number in hairy bittercress but not in thale cress. One way that LEAFY regulates petal development is by turning on expression of the APETALA1 gene. Other regulators in thale cress but not in hairy bittercress also turn on this gene. We want to know whether this difference in gene regulation plays a part in making these two species look different from each other. Here, we will determine whether LEAFY or a different gene controls the variation observed in hairy bittercress populations. We will also identify genes that act only in hairy bittercress to reduce petal number. Many of the genetic changes during evolution that produce different-looking species result from changes in the way genes are regulated and we will test whether this is true for the APETALA1 gene in these two mustard species. Thus, species-specific differences in petal number between hairy bittercress and thale cress, and natural variation in this trait between hairy bittercress populations around the world, provide an exciting experimental platform to trace evolution from specific changes in gene regulation through to altered morphologies in nature. Another group of mustards called Brassicas are remarkable for containing more important agricultural and horticultural crops than any other plant genus. Understanding the genetic basis of mustard diversity is therefore a vital part of generating crops for the 21st century.