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The Primula S locus: gene function and the maintenance and breakdown of heterostyly

报春花 S 基因座：基因功能以及异柱性的维持和分解

基本信息

批准号：
BB/P022081/1
负责人：
Philip Gilmartin
金额：
$ 93.7万
依托单位：
University of East Anglia
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FP022081%2F1
关键词：
Primula locus gene function maintenance

项目摘要

Pollination is important, ~70% of our food results directly from pollination as seeds, grains, fruits and berries. It is important to plants too for reproduction, which not only produces the next generation but creates variation upon which natural selection can act. This variation enables plants to adapt to changing environments and colonize new habitats. Most plants produce hermaphrodite flowers, but plants cannot move or actively choose a partner, instead they have evolved intriguing strategies to prevent self-pollination and promote cross-pollination. One of the most remarkable of these strategies is heterostyly, which uses insect pollinators (hetero=different; style=female structure). Charles Darwin observed that Primroses have two forms of flower, pin with a long style and short stamens, and thrum with a short style and longs stamens. These reciprocal positions facilitate pollen transfer by insect visitors between each flower type. A group of genes, known collectively as the S locus, controls development of the two forms of flower. A rich history of scientific research on Primroses by early botanists and geneticist made heterostyly an important textbook example of a plant breeding system. Our study will add to this work by using the latest research tools to explore how heterostyly arose, how it is controlled and why it occasionally goes wrong.We sequenced the Primrose (Primula vulgaris) genome and identified a group of five genes that control development of its two flower types. These genes are found only in thrum and are absent in pin plants. Only those individuals that inherit this gene cluster can produce thrum flowers. Our studies show the gene which we believe is responsible for elongating stamens in thrum flowers arose ~51.7million years ago in an ancestor of all modern Primula species. We have also identified the gene responsible for controlling style length. The gene cluster contains a further three genes and in this study we will characterize their function to determine how they work together to control the floral architectures of pin and thrum flowers that facilitate insect-mediated pollination in the Primrose. Over the past 51.7 million years, 30 different species of Primula have lost the ability to produce two types of flower, they all have long styles and long stamens and never produce short styled flowers. These homostyles (Homo = same) do not use insect pollinators, but self-fertilize. Our studies suggest the gene that controls style length has been lost or damaged in these species.These homostyle species provide an exciting opportunity to explore how one gene has, over time, on multiple separate occasions, been lost or damaged during the evolution of the different Primula species. This is important because understanding how development has gone wrong can help explain how it normally works. We will use our Primrose genome sequence to identify and characterize the corresponding S locus gene clusters in these different Primula species to discover the gene mutation that has resulted in the loss of heterostyly. Most plant and animal genes are present in two copies, one set from the mother, one from the father; this is useful, if one copy is damaged, the second copy acts as backup so function is retained, it also enables repair of the damaged copy using the other as a template. This arrangement provides genetic stability from generation to generation. One very surprising finding from our studies of genes controlling heterostyly in Primula is that they are present only as a single copy, there is no back up copy. It is therefore surprising that heterostyly is stable as any genetic damage to the key genes cannot be repaired. We do not yet have an explanation for this conundrum but our project will initiate studies to seek an explanation.

授粉很重要，我们食物的70%直接来自授粉，如种子，谷物，水果和浆果。它对植物的繁殖也很重要，繁殖不仅产生下一代，而且创造了自然选择所能作用的变异。这种变异使植物能够适应不断变化的环境并殖民新的栖息地。大多数植物产生两性花，但植物不能移动或主动选择伴侣，相反，它们进化出了有趣的策略来防止自花授粉并促进异花授粉。其中最引人注目的策略之一是异花柱，它使用昆虫授粉（异=不同;风格=女性结构）。查尔斯达尔文观察到报春花有两种形式的花，长花柱和短雄蕊的针，短花柱和长雄蕊的线。这些相互的位置促进了昆虫访客在每种花类型之间的花粉转移。一组基因，统称为S基因座，控制着两种花的发育。早期植物学家和遗传学家对报春花进行了丰富的科学研究，使异型花柱成为植物育种系统的重要教科书范例。我们的研究将通过使用最新的研究工具来探索异花柱是如何产生的，它是如何控制的，以及为什么它偶尔会出错，从而为这项工作增添新的内容。我们对报春花（Primula vulgaris）的基因组进行了测序，并确定了一组控制其两种花型发育的五个基因。这些基因只存在于有丝植物中，而在针叶植物中不存在。只有那些继承了这个基因簇的个体才能产生线花。我们的研究表明，我们认为负责延长线花雄蕊的基因出现在大约5170万年前的所有现代报春花物种的祖先中。我们还确定了控制花柱长度的基因。该基因簇包含另外三个基因，在这项研究中，我们将表征它们的功能，以确定它们如何共同努力，以控制针和thrum花，促进昆虫介导的授粉在报春花的花结构。在过去的5170万年里，30种不同的报春花已经失去了产生两种花的能力，它们都有长花柱和长雄蕊，并且永远不会产生短花柱的花。这些同柱体（Homo =相同）不使用昆虫传粉者，而是自花受精。我们的研究表明控制花柱长度的基因在这些物种中已经丢失或受损。这些同花柱物种提供了一个令人兴奋的机会来探索一个基因如何随着时间的推移，在多个不同的场合，在不同报春花物种的进化过程中丢失或受损。这一点很重要，因为理解开发是如何出错的有助于解释它通常是如何工作的。我们将使用我们的报春花基因组序列，以确定和表征相应的S位点基因簇在这些不同的报春花物种，以发现基因突变，导致了损失的异型花柱。大多数植物和动物基因都有两个拷贝，一个来自母亲，一个来自父亲;这是有用的，如果一个拷贝被损坏，第二个拷贝作为备份，因此功能被保留，它还可以使用另一个作为模板修复损坏的拷贝。这种安排提供了一代又一代的遗传稳定性。我们在研究报春花中控制异型花柱的基因时有一个非常令人惊讶的发现，它们只以单一拷贝存在，没有备份拷贝。因此，令人惊讶的是，异型花柱是稳定的，因为对关键基因的任何遗传损伤都无法修复。我们还没有一个解释这个难题，但我们的项目将启动研究，以寻求解释。