Unconventional ubiquitin chains as regulators of plant development

除了在蛋白质分解中已被公认的作用外，小修饰蛋白泛素在动物和酵母中作为可逆标记也具有重要的功能。然而，这种功能在很大程度上还没有在植物中被探索出来。申请人以前的工作表明，在两个相关泛素连接酶中有损伤的拟南芥植株表现出完全的顶端优势，即突变植株没有抑制同一植株上附加枝条生长的主枝。这些连接酶具有通过泛素的LYS63连接的泛素链形成的特异性。这种链并不以蛋白质分解的底物为目标，而是作为分子开关促进新的蛋白质相互作用。我们希望通过鉴定底物和深入研究这些泛素连接酶调节植物激素代谢的那些方面，来研究连接酶在发育过程中的整合。

In addition to the well-established role in proteolysis, the small modifier protein ubiquitin has important functions as a reversible tag in animals and in yeast. Such functions are, however, largely unexplored in plants. Previous work by the applicant indicated that Arabidopsis plants with lesions in two related ubiquitin ligases show complete loss of apical dominance, i. e. mutant plants do not have a main shoot that suppresses the outgrowth of additional shoots on the same plant. The ligases were characterized to have specificity for formation of ubiquitin chains linked via Lys 63 of ubiquitin. Such chains do not target substrates for proteolysis, but facilitate novel protein interactions as molecular switches. We want to investigate the integration of the ligases into developmental processes by identification of substrates, and by in-depth investigation of those aspects of plant hormone metabolism that were shown to be regulated by these ubiquitin ligases.