HUA1 AND HUA2 IN ARABIDOPSIS FLOWER DEVELOPMENT

我们对多细胞生物发展的一个基本问题感兴趣，即一些未分化的细胞如何承担它们的身份并形成独特的模式。我们选择在拟南芥流发育的背景下解决这个问题。特别是，我们正在研究前体细胞如何进行鉴定并发育成雄蕊和心皮，即花的雄性和雌性生殖器官。长期以来，MADS结构域转录因子AG是唯一已知参与这一发育过程的蛋白质。目前尚不清楚单个转录因子是如何导致诸如雄蕊和心皮等复杂器官的最终形成的。我们的长期目标是全面剖析AG通路，以了解这一复杂的发育过程。AG通路的两个新成员，HUA1和HUA2，利用弱AG等位基因从我们的增强子筛选中分离出来。HUA2是用基于地图的策略克隆的。它编码一种推定的AG转录因子和转录辅激活因子。对HUA1的克隆已取得重大进展。本研究旨在揭示HUA1和HUA2在拟南芥花发育中的分子机制。首先，将在蛋白质水平上研究HUA2。确定HUA2蛋白在植物内的定位模式。我们将进行实验来研究AG和HUA2之间的物理相互作用，这是我们在初步研究中观察到的。我们的产物与HUA2相互作用的基因将用酵母双杂交筛选分离出来。第二，对HUA1进行克隆并在分子水平上进行研究。它在植物内的RNA定位模式将被确定。HUA1， HUA2和AG蛋白之间潜在的相互作用将被研究。第三，将进一步分离出HUA1和HUA2的突变等位基因，特别是严重的功能缺失突变，这将有助于解决一些悬而未决的关于HUA1和HUA2在AG通路中功能的问题。T-DNA插入系分子筛选和Hua1 Hua2增强子筛选的结合将用于此目的。对拟南芥同源途径的详细了解将是对我们一般发育过程知识的宝贵补充。植物和动物同源途径可以与衍生的进化原理相比较。此外，在拟南芥这样的简单生物中研究植物的发育可能会加快我们对更复杂生物（如人类）的理解。鉴于HUA2与秀丽隐杆线虫、果蝇、小鼠和人类的基因具有共同的基序，一些植物基因在同型同源途径中的分子功能在动物中被保守也就不足为奇了。

We are interested in a fundamental issue in the development of multicellular organisms, i.e., how a few undifferentiated cells assume their identities and form distinct patterns. We have chosen to address this issue in the context of Arabidopsis flow development. In particular, we are studying how precursor cells assume their identifies and develop into stamens and carpels, the male and female reproductive organisms of the flower. For a long time, AG, a MADS domain transcription factor, was the only known protein involved in this developmental process. It is not clear how a single transcription factor leads to the eventual formation of complex organs such as stamens and carpels. It is our long-term goal to fully dissect the AG pathway in order to understand this complex developmental process. Two new members of the AG pathway, HUA1 and HUA2, were isolated from our enhancer screen using a weak ag allele. HUA2 was cloned with a map-base strategy. It codes for a putative transcription factor and transcriptional co-activator of AG. Significant progress has been made towards the cloning of HUA1. This proposal is aimed at uncovering the molecular mechanisms underlying the functions of HUA1 and HUA2 in Arabidopsis flower development. First, HUA2 will be studied at the protein level. HUA2 protein localization pattern within the plant will be determined. Experiments will be performed to study the physical interaction between AG and HUA2, which was observed in our preliminary studies. Our genes whose products interact with HUA2 will be isolated with a yeast two-hybrid screen. Second, HUA1 will be cloned and studied at the molecular level. Its RNA localization patterns within the plant will be determined. Potential interactions among HUA1, HUA2 and AG proteins will be investigated. Third, additional mutant alleles of HUA1 and HUA2 will be isolated, especially severe loss-of-function mutations, which will help solve some pending issues regarding the functions of HUA1 and HUA2 in the AG pathway. A combination of a molecular screen of T-DNA insertional lines and a Hua1 Hua2 enhancer screen will be employed for this purpose. A detailed understanding of a homeotic pathway in Arabidopsis will be an invaluable addition to our knowledge of developmental process in general. Plant and animal homeotic pathways can be compared to derived evolutionary principles. In addition, studying plant development in a simple organism like Arabidopsis will likely expedite our understanding of more complicated organisms such as humans. In light of the fact that HUA2 shares common motifs with genes in C. elegans, Drosophila, mice and humans, it will not be surprising that the molecular functions of some plant genes in homeotic pathways are conserved in animals.