Mechanismen der pflanzlichen Entwicklung: Die Rolle der Steroide in der Embryogenese von Arabidopsis

拟南芥的胚胎发生是一个定型的发育过程，是通过特定基因的功能精心安排的。三个突变体cephalopod （cph）、fackel （fk）和hydral （hydl）在胚胎发育过程中缺乏正常的细胞形态和模式形成缺陷。相应的基因编码甾醇生物合成酶：CPH，一种C-24甲基转移酶；C-14还原酶FK；和HYD1，一个c -8,7异构酶。这些发现表明类固醇分子在植物早期发育中起着关键作用。在动物细胞中，胆固醇对细胞膜的完整性很重要，此外还可以作为胚胎发生所需的类固醇激素的过饱和物。迄今为止发现的唯一的植物类固醇激素是油菜素内酯（BRs），它是胚胎后细胞扩增所必需的，但尚未被证明是胚胎发育中细胞形态发生所必需的。本课题通过CPH、FK和HYD1的蛋白定位研究，探讨类固醇生物合成在植物中的作用。此外，在植物同源结构域亮氨酸拉链转录因子亚类中发现的甾醇结合的候选结构域START的功能将被研究在甾醇信号转导中的假定作用。

Embryogenesis in Arabidopsis is a stereotyped developmental process that is orchestrated through the functions of specific genes. Three mutants, cephalopod (cph), fackel (fk) and hydral (hydl), lack normal cell morphology and show defects in pattern formation during embryonic development. The corresponding genes encode sterol biosynthesis enzymes: CPH, a C-24 methyltransferase; FK, a C-14 reductase; and HYD1, a C-8,7 isomerase. These findings suggest that steroid molecules play critical roles in early plant development. In animal cells, cholesterol is important for the integrity of the cell membranes and in addition serves as a percursor for steroid hormones required in embryogenesis. The only plant steroid hormones identified thus far are the brassinosteroids (BRs), which are needed for postembryonic cell expansion, but have not been shown to be required for cell morphogenesis in embryonic development. The projects described in this proposal probe the role of steroid biosynthesis in plants via protein localization studies of CPH, FK and HYD1. Further, the function of START, a candidate domain for sterol-binding found in a subclass of plant homeodomain-leucine zipper transcription factors, will be examined for a putative role in sterol signal transduction.