Genetic Studies of ASK Gene Functions

植物的发育需要多种基因产物的协调活动，这可以在蛋白质合成和降解水平上进行调节。许多控制花发育的调控基因编码可能的转录因子，但很少有人知道调控蛋白分解。由NSF拨款支持的工作表明，拟南芥ASK1基因调节营养和花的发育，并编码酵母和人类Skp1蛋白的同源物。Skp1是SCF泛素连接酶复合体的一个亚基，催化泛素与靶蛋白共价连接的第三步，介导蛋白质的降解。ASK1与UFO在基因上相互作用，调控花发育和花基因APETALA3(AP3)和雌蕊(PI)的表达。工作模式是UFO和ASK1是SCF泛素连接酶的组成部分，促进AP3和PI表达的负调控因子的降解。此外，ASK1在雄性减数分裂I的同源分离和分离中是必不可少的。在减数分裂I中，特定的蛋白质必须在中期/后期被降解才能分离同源。因此，最简单的假设是ASK1调节这种蛋白降解事件。拟南芥至少有20个Skp1同源基因，命名为Asks。其他ASK基因的功能尚不清楚。酵母Skp1基因对有丝分裂的生长是必不可少的，这一事实表明其他ASK基因(S)可能具有共同控制基本细胞过程的冗余功能。因此，了解ASK基因的其他功能应该会为调节蛋白分解在发育过程中的作用提供新的见解。在这个项目中，ASK1在调控花发育中的功能将进一步用遗传学和分子方法进行分析，包括UFO和ASK1之间在AP3和PI表达调控方面的相互作用。此外，ASK1在减数分裂I中控制同源分离中的作用将使用显微程序进行研究。此外，更多的ASK基因将通过表达研究和与ASK1的功能比较来表征，其中一些在花中表达的ASK基因将使用反向遗传方法进行功能测试。这些实验可能会为植物生殖发育如何受基因调控提供新的见解，从而可能使农业和环境受益。在拟南芥测序刚刚完成的时候，对基因功能的研究是及时和有益的。这些实验的结果也可能为植物学家社区中的许多人以及那些研究非植物生物的人未来的研究提供起点。

Plant development requires the coordinated activity of many gene products, which can be regulated at both the levels of protein synthesis and degradation. Many regulatory genes controlling flower development encode putative transcription factors, but few are known to regulate proteolysis. Work supported by an NSF grant indicates that the Arabidopsis ASK1 gene regulates vegetative and flower development and encodes a homolog of the yeast and human SKP1 protein. SKP1 is a subunit of SCF ubiquitin ligase complexes that catalyze the third step of a pathway that covalently links ubiquitins to target proteins, mediating the degradation of proteins. ASK1 interacts with UFO genetically to regulate flower development and the expression of the floral genes APETALA3 (AP3) and PISTILLATA (PI). The working model is that UFO and ASK1 are components of a SCF ubiquitin ligase that facilitates the degradation of a negative regulator of AP3 and PI expression. Furthermore, ASK1 is essential for homolog separation and segregation during male meiosis I. In meiosis I, specific proteins must be degraded at the metaphase/anaphase transition to allow the separation of homologs. Therefore, the simplest hypothesis is that ASK1 regulates such a proteolytic event. Arabidopsis possesses at least 20 SKP1 homologs, named ASKs. The functions of the other ASK genes are not known. The fact that the yeast SKP1 gene is essential for mitotic growth suggests that other ASK gene(s) probably have redundant functions that together control essential cellular processes. Therefore, understanding other ASK gene functions should provide new insights into the role of regulated proteolysis during development. In this project, the ASK1 function in regulating flower development will be further analyzed using genetic and molecular approaches, including the interaction between UFO and ASK1 in the context of regulation of AP3 and PI expression. In addition, the role of ASK1 in controlling homolog separation in meiosis I will be investigated using microscopic procedures. Moreover, additional ASK genes will be characterized by expression studies, by functional comparison with ASK1, and some of those ASK genes expressed in the flowers will be tested for function using reverse genetic approaches. These experiments will likely provide new insights about how plant reproductive development is regulated by genes, potentially benefiting agriculture and the environment. The study of gene functions when the Arabidopsis sequencing has is just been completed is both timely and beneficial. The results from these experiments will also likely provide the starting points for future research by many in the community of plant scientists as well as those studying non-plant organisms.