雄蕊特征决定相关的MADS基因对光合基因表达的影响及其在生殖细胞诱导发生中的作用研究

Development is a morphogenetic process genetically programmed and cyclical. Germ cells are key nodes connecting two generations. In animals, germ cells are specified sooner after zygote dividing either by "preformation" or by induction, and migrate to gonads, localize and differentiate there as germlines. In plants, germ cells (also called as microsporocytes or macrosporocytes) are induced from somatic cells at particular regions in primordia of reproductive organs such as stamens or carpels (should be precisely ovules); which are initiated long after zygote dividing. Some genes are known for their roles in germ cell induction and their population size, but still, little is known about the regulatory mechanism. In our previous work on molecular description of early stamen development in rice, we found one of the C-class MADS-box genes OsMADS58 is involved in regulation of photosynthetic genes in stamen, and consistent with the low expression of photosynthetic genes, there is no distinguishable chloroplasts in stamen cells. Recently, Walbot lab reported that in maize stamen, hypoxia triggers meiotic fate acquisition. Taken the findings from the two labs together, we hypothesize that the ultimate role of stamen is to create an optimal microenvironment for facilitating the induction of germ cells from somatic cells. In rice stamen, one of mechanisms to achieve it seems to be shutting down photosynthesis, which is O2 generating process, by using so called "organ identity gene" to repress photosynthetic gene expression and resulting in block of chloroplast development. The latter are observed in our previous investigation. To test this attractive hypothesis, we designed a comparative strategy. Additional to conventional experiments to further uncover the molecular mechanism how OsMADS58 regulates its target photosynthetic genes, we would examine if there is no chloroplast in maize stamen and if the regulatory relationship between C-class MADS-box genes and photosynthetic genes are also observed in maize stamen. More excitedly, we would artificially duplicate C-class gene in Arabidopsis, which has only one member, AG, by transforming OsMADS58 in an organ specific manner, to see if the artificial duplication of C-class gene would mimic the situation observed in rice and maize stamen in Arabidopsis, as both rice and maize have multiple copies of C-class genes.

发育是一个代代重演的遗传程序控制的形态建成过程。生殖细胞是连接两个世代的重要节点细胞。在动物中，生殖细胞在受精卵开始分裂后很快就完成命运决定而形成生殖细胞系。在植物中，则要在生殖器官（如雄蕊）原基发生后才开始由其中特定区域的体细胞被诱导发生。尽管目前已知一些基因影响雄蕊中生殖细胞（小孢子母细胞）的发生与数量，但相关调控机制知之甚少。本实验室前期工作表明水稻与雄蕊器官特征形成有关的C类基因之一OsMADS58参与对光合基因表达的调控、雄蕊中没有叶绿体存在；其他实验室报道玉米雄蕊中还原态有利于生殖细胞发生。据此，我们认为，OsMADS58类基因对光合基因表达的调控，可能是通过抑制叶绿体发育而创造有利于生殖细胞诱导发生的还原性微环境。为检验这一假设的真实性，本项目设计了一套比较研究的策略，分析相关MADS基因对光合基因的调控、叶绿体发育与氧化还原状态、及它们对生殖细胞诱导发生的影响三者间的关系。