RESEARCH-PGR: Genomic mechanisms of domesticating a Y chromosome in papaya

研究-PGR：木瓜 Y 染色体驯化的基因组机制

• 批准号: 1546890
• 负责人: Ray Ming
• 金额: $ 216.6万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1546890&HistoricalAwards=false
• 关键词: RESEARCH; PGR; Genomic; mechanisms; domesticating

Many plants have male and female floral parts housed on the same plant. Papaya plants, on the other hand, are gender-distinct: papaya plants may be male or female or so-called hermadrodites, which are plants that both male and female parts in the same flowers. Wild papayas are male and female only, and cultivated papayas are mostly hermaphrodite, which was selected from sex reversed male papaya about 4,000 years ago in Central America. Understanding how this rare gender biology is controlled, and whether hermaphroditism could be harnessed for control of flowering, would greatly benefit agriculture of papaya. It is currently known that the difference among these trees is due to different Y chromosomes: females have two X chromosomes, males have an X and Y and hermaphrodites an X and modified Yh. There is also evidence that hermaphrodite chromosome may have evolved during the earliest days of domestication of papaya in Central America. The project will identify what factors and genome-wide changes are occurring in the plants with varying chromosome types. Once identified, plants could be engineered to produce hermaphrodites with no X chromosome, hence no segregation of types. This material will expedite the identification of the factors that control the formation of male flowers, the target for sex reversal from male back to hermaphrodite. Undergraduate students will be trained to gain hands-on research experience while working with this important crop and developing breeding tools. The project will display information for growers on informative videos about papaya biology and ways to control flowering. Papaya sex chromosomes are the first trio (Y, Yh, and X) to be sequenced. The unique set of three sex chromosomes and abundant genomic and biological resources allow us to investigate the reversion from male to hermaphrodite, a rare event during the early stage of sex chromosome evolution. Our goal is to understand the genomic and evolutionary mechanisms governing the domestication of the Yh chromosome. The first aim is to establish the molecular basis for papaya YY lethality gene and restore fertility of YhYh hermaphrodite and YhY male genotypes for functional analysis of Yh-specific genes. A strong candidate gene has been identified and is being tested for function by being transformed into hermaphrodite plants. Once viable YhYh hermaphrodites are generated, the 40 mutations on Y chromosome affecting flower morphology and pollen fertility will be identified through fine mapping. The second aim is to identify the sex determination gene suppressing carpel development in male flowers and the mutation event leading to the sex reversal from male back to hermaphrodite. The project is focusing on 12 sex reversal mutants generated for identification of the sex determination gene suppressing carpel development in male flowers, and will conduct map based gene cloning once the YYh fertility is restored. Comparative analysis of gene expression between YY and Yh Yh genotypes will reveal differentially expressed genes and gene networks controlled by the sex determination gene. The target genes and genomic resources generated will lead to selection of new papaya varieties without segregation of sex types and with improved productivity

许多植物有雄性和雌性花部分安置在同一植物上。另一方面，木瓜植物是性别不同的：木瓜植物可以是雄性或雌性或所谓的hermadrodites，这是在同一朵花中具有雄性和雌性部分的植物。野生木瓜只有雄性和雌性，而栽培木瓜大多是雌雄同体，这是大约4,000年前在中美洲从性别逆转的雄性木瓜中选出的。了解这种罕见的性别生物学是如何控制的，以及雌雄同体是否可以用来控制开花，将大大有利于木瓜农业。目前已知，这些树之间的差异是由于不同的Y染色体：女性有两个X染色体，男性有X和Y，雌雄同体的X和修改的Yh。也有证据表明，雌雄同体的染色体可能是在中美洲木瓜驯化的最早时期进化出来的。该项目将确定在具有不同染色体类型的植物中发生了哪些因素和全基因组变化。一旦确定，植物可以被改造成没有X染色体的雌雄同体，因此没有类型分离。这一材料将加快确定控制雄花形成的因素，雄花是从雄性到雌雄同体的性别逆转的目标。本科生将接受培训，以获得实践研究经验，同时与这种重要的作物和开发育种工具。该项目将为种植者展示有关木瓜生物学和控制开花方法的信息视频。木瓜的性染色体是第一个被测序的三重染色体（Y，Yh和X）。独特的三条性染色体和丰富的基因组和生物资源使我们能够研究性染色体进化早期罕见的雄性到雌雄同体的逆转。我们的目标是了解基因组和进化机制的Yh染色体的驯化。 本研究的第一个目的是建立番木瓜YY致死基因的分子基础，恢复YhYh雌雄同体和YhY雄性基因型的育性，为Yh特异基因的功能分析奠定基础。 一个强有力的候选基因已经被确定，并正在通过转化到雌雄同体植物中来测试其功能。一旦产生有活力的YhYh两性体，将通过精细定位来鉴定Y染色体上影响花形态和花粉育性的40个突变。第二个目的是鉴定抑制雄花心皮发育的性别决定基因，以及导致雄花性逆转为两性花的突变事件。该项目的重点是12个性别逆转突变体，用于鉴定抑制雄花心皮发育的性别决定基因，一旦YYh恢复育性，将进行基于图的基因克隆。比较分析YY和Yh Yh基因型之间的基因表达，将揭示性别决定基因控制的差异表达基因和基因网络。 所产生的目的基因和基因组资源将导致选择新的番木瓜品种，而不分离的性别类型和提高生产力