Ovule Development in Higher Plants

小行星9505813 胚珠是植物生殖的基本单位，它产生雌配子体，介导受精过程，并支持胚胎的发育。这项提案的长期目标是通过分析Fischer博士实验室克隆的两个拟南芥基因BELL 1（BEL 1）和OVULE MUTATION 2（OVM 2）来了解控制胚珠早期发育的遗传电路。BEL 1基因产物在胚珠身份的特化中起作用。BEL 1突变体胚珠通常转化为心皮样结构，BEL 1基因的分离和测序表明它编码一个同源域转录因子。据认为，BEL 1基因通过负调控花同源异型基因AGAMOUS（AG）的表达来阻止心皮发育程序凌驾于胚珠发育之上。OVM 2基因产物需要在不同的阈值水平，以控制胚珠和雌配子体发育，分别。在没有活性OVM 2蛋白的情况下，胚珠和雌配子体发育都受到显著抑制，而低水平的OVM 2蛋白导致无功能的胚珠，特别是缺乏雌配子体。OVM 2基因的分离和测序表明，它与花同源异型基因APETALA 2（AP 2）有关。因此，BEL 1和OVM 2基因是胚珠和雌配子体发育的重要调控因子，其突变导致器官的同源异型转化和缺失。为了了解它们的作用机制，控制早期胚珠发育的关键步骤，以及胚珠和花发育程序之间的关系，将进行实验：1）确定BEL 1和OVM 2活性的时空定位; 2）确定胚珠和花调控基因之间的遗传关系; 3）进行BEL 1和OVM 2功能的分子分析，和4）进行遗传筛选以鉴定控制巨配子发生的新基因。 ***

9505813 Fischer The ovule is a fundamental unit of plant reproduction that generates the female gametophyte, mediates fertilization processes, and support the development of the embryo. The long term goal of this proposal is to understand the genetic circuits that control the early development of the ovule by analyzing two Arabidopsis genes, BELL1 (BEL1) and OVULE MUTATION2 (OVM2), that were cloned in Dr. Fischer's laboratory. The BEL1 gene product plays a role in the specification of ovule identity. bel1 mutant ovules are often transformed into carpel like structures, isolation and sequencing of the BEL1 gene indicates that it encodes a homeodomain transcription factor. It is thought that the BEL1 gene prevents the carpel developmental program from over-riding ovule development by negatively regulating expression of the floral homeotic gene, AGAMOUS(AG). The OVM2 gene product is needed at distinct threshold levels to control ovule and female gametophyte development, respectively. With no active OVM2 protein, both ovule and female gametophyte development are dramatically suppressed, whereas a low level of OVM2 protein results in nonfunctional ovules that specifically lack a female gametophyte. Isolation and sequencing of the OVM2 gene indicates that it is related to the floral homeotic gene APETALA2 (AP2). Thus, BEL1 and OVM2 genes are important regulators of ovule and female gametophyte development, with mutations resultilg in homeotic conversions and deletions of organs. To understand their mechanism of action, the critical steps that control early ovule development, and the relationship between ovule and floral developmental programs, experiments will be carried out to: 1) Determine the temporal and spatial localization of BEL1 and OVM2 activity, 2) Determine the genetic relationships between ovule and floral regulatory genes, 3) Carry out a molecular analysis of BEL1 and OVM2 function, and 4) Carry out a genetic screen to identify new genes that control megagametogenesis. ***