Sex Determination in the Homosporous Fern Ceratopteris richardii

羊草的配子体不是两性的就是雄性的。在这种和许多其他蕨类植物中，性别决定的主要信号是雄激素，一种由配子体分泌的类似赤霉素的信息素。在它的存在下，幼年配子体发育为雄配子体，而在没有它的情况下，幼体发育为纹藻。这项建议的主要目标是使用遗传和分子相结合的方法来了解雄蕊原是如何控制Ceratopteris配子体的性别的。其具体目标是：1)通过产生和表征突变来识别与性别决定有关的关键调控基因；以及2)利用基因表达筛选来分离表达因去雄激素而改变的基因，该基因表达筛选通过消减杂交方法鉴定两个mRNA群体之间丰度不同的mRNAs；然后通过在转基因植物中表达它们的反义cDNA来评估它们的表达的时间和空间模式，并研究它们的功能。%这种对角翅目昆虫性别决定过程的分析可能会促进我们对高等植物中类似过程的一般理解，也将涉及到与所有生物体生殖发育有关的基因的激素控制的更一般问题。

Gametophytes of the fern ceratipteris richardii are either hermaphroditic or male. The primary sex-determining signal in this and many other ferns is antheridiogen, a gibberellin-like pheromone that is secreted by the gametophyte. In its presence, a juvenile gametophyte develops as a male, whereas in its absence, the juvenile develops as a hermaphoxlite. The primary objective of this proposal is to use a combined genetic and molecular approach to understand how antheridiogen governs the sex of the gametophyte of Ceratopteris. The specific objectives are 1) to identify key regulatory genes involved in sex determination by generating and characterizing mutations; and 2) to isolate genes whose expression is altered in response to antheridiogen using a gene expression screen which identifies mRNAs that differ in abundance between two mRNA populations by a subtractive hybridization method; the temporal and spatial patterns of their expression will then be assessed and their function investigated by expressing their antisense cDNA in transgenic plants. %%% This analysis of the sex determining process in Ceratopterts may advance our general understanding of similar processes in higher plants, and will also relate to more general questions concerning hormonal control of genes involved in the reproductive development of all organisms.