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身体特征。开花植物的物种数量和多样性是地球上所有植物群中最多的，而花瓣通过吸引不同的传粉者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毛茸茸的苦菜等杂草来说是有利的。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这些机制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个芥菜物种之间花瓣数量变化的遗传变化，这两个物种是模式生物水芹(拟南芥)和多毛苦菜(碎米豆蔻)。这些物种关系密切，易于在实验室进行研究，因此可以利用遗传和转基因实验来识别使这两个物种看起来不同的机制。水芹具有典型的芥末花，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，毛茸茸的苦菜基因组的一个区域控制了该物种观察到的花瓣数量的大量变异。我们还知道一个控制花瓣发育的重要基因LEAFY定位到这个基因组区域。为了鉴定抑制多毛苦菜花瓣数目的基因，我们通过诱变在基因组中诱导了变异，并鉴定了将有毛苦菜转化为水芹花瓣数目的突变体。识别这些植物中突变的基因将告诉我们，哪些基因可以减少多毛苦菜的花瓣数量，而不能减少水芹的花瓣数量。LEAFY调节花瓣发育的一种方式是通过启动APETALA1基因的表达。除了毛茸茸的苦菜外，其他调节基因也开启了这一基因。我们想知道基因调控上的差异是否在导致这两个物种看起来不同的原因中起到了作用。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茸茸的苦菜中起作用的基因，以减少花瓣数量。进化过程中产生不同物种的许多遗传变化是由于基因调控方式的变化，我们将测试这两个芥末物种的APETALA1基因是否如此。因此，多毛苦菜和水芹在花瓣数量上的物种差异，以及世界各地多毛苦菜种群之间这一特征的自然变异，为追踪从基因调控的特定变化到自然界中的形态变化的进化提供了一个令人兴奋的实验平台。另一类被称为芥菜的芥菜比其他任何一种植物都含有更多重要的农业和园艺作物。因此，了解芥菜多样性的遗传基础是为21世纪生产作物的关键部分。

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.