The Genetic and Molecular Basis of Sex Determination in Ceratopteris

9723154银行技术组瑞氏蕨类植物的配子体是两性或雄性的二态植物。在这种蕨类植物和其他蕨类植物中，性别的决定因素是雄激素，一种由两性配子体分泌的类似赤霉素的信息素，它促进其他性别未确定的配子体的雄性发育。植物激素脱落酸阻止了花粉原的反应。通过产生和表征改变配子体正常性别的突变，已经确定了几个涉及性别决定的关键调控基因。对这些突变体的遗传分析定义了一个至少由8个相互作用的基因组成的调控网络，这些基因与性别类型有关。其中有两个主要的性别决定基因，TRA-1和FEM1，它们的活性分别是促进雌性和雄性性状分化所必需的。每个基因还负向调节另一个基因的表达，因此配子体的性别最终取决于哪个基因最先表达。雄激素通过调节TRA-1的活性激活由HER基因决定的信号转导途径，从而影响配子体的性别。这种性别决定模型将通过继续对新的和现有的性别决定突变的遗传和形态分析来检验。其中一个基因，Ceratopteris的Knoted-1同源基因，可能也参与两性分生组织的发育，并在雄性发育过程中成为雄核诱导剂抑制的目标。还分离出了几个因暴露于外源花粉诱导剂而上调的基因，并将确定这些基因的功能。最终的目标是开发一种农杆菌介导的蕨类植物转化系统。如果成功，将引入玉米的Ac/DS转座元素，并测试它们在蕨类植物中的转座能力。如果它们是可移动的，将寻找由转座子标签诱导的突变。非技术部门如何决定植物的性别是一个重要的发展问题，其答案最终可能在农业和植物育种中具有实际应用。这项拟议的研究将提供对性别决定基因的基本了解，以及已知信息素和激素线索的信号通路。***

9723154 Banks Technical section Gametophytes of the fern Ceratopteris richardii are sexually dimorphic, either hermaphroditic or male. The determinant of sex in this and other ferns is antheridiogen, a gibberellin-like pheromone that is secreted by the hermaphroditic gametophytes and which promotes male development of other sexually undetermined gametophytes. The plant hormone abscisic acid blocks the antheridiogen response. Several key regulatory genes involved in sex determination have been identified by generating and characterizing mutations that alter the normal sex of the gametophyte. A genetic analysis of these mutants defines a regulatory network of at least eight interacting genes that are involved in determining sex type. Among these are two major sex-determining genes, TRA-1 and FEM-1, whose activities are required to promote the differentiation of female and male traits, respectively. Each gene also negatively regulates the expression of the other such that the sex of the gametophyte ultimately depends on which gene is expressed first. Antheridiogen activates a signal transduction pathway defined by the HER genes which affects the sex of the gametophyte by regulating the activity of TRA-1.This model of sex determination will be tested by continuing the genetic and morphological analysis of new and existing sex-determining mutants. One such gene, a Ceratopteris homolog of KNOTTED-1 is likely to also be involved in meristem development in the hermaphrodite and a target of repression by antheridiogen during male development. Several genes that are up-regulated in response to exposure to exogenous antheridiogen have also been isolated and the functions of these genes will be determined. A final objective is to develop an Agrobacterium-mediated transformation system in the fern. If successful, the Ac/Ds transposable elements of maize will be introduced and their ability to transpose in the fern will be tested. If they are mobile, mutants induced by transposon tagging will be sought . Non-technical section How sex is determined in plants is an important developmental question whose answer may ultimately have practical applications in agriculture and plant breeding. The proposed studies will provide a basic understanding of the genes involved in sex determination and the signaling pathway for known pheromonal and hormonal cues. ***