蕨类植物性别分化对环境的响应

蕨类植物是维管植物中唯一的孢子体和配子体都能独立生活的类群.同型孢子蕨类配子体的性别分化受到激素和环境因子的影响.生理学研究表明,成精子囊素与赤霉素能诱导雄配子体发育,抑制雌配子体发育;脱落酸阻止成精子囊素诱导的精子器形成;乙烯合成前体ACC促进赤霉素诱导的精子器形成,而乙烯合成抑制因子AOA通过抑制细胞分化来抑制精子器形成.光照对不同种类蕨类配子体分化的影响存在差异.糖类能够促进雄配子体形成,并可加速成熟雌配子体向两性分化.钙离子、钴离子和甲硫氨酸等分别参与了蓝光和赤霉素对配子体性别分化的调控过程.培养密度影响配子体生长及性别表达,高密度下雄性和无性配子体居多,而低密度下两性和雌性配子体居多.近年来的突变体表型分析与分子生物学研究表明,成精子囊素通过影响ANI1、HER、TRA、FEM和MAN等基因的表达调控配子体性别分化.综述了蕨类植物性别分化对环境响应的研究进展.

Sex differentiation in ferns response to environmental factors

The life cycle of ferns involves a small, haploid gametophyte alternating with a large, independent, diploid sporophyte. Since spore germination and free-living gametophyte development are completely independent of the diploid sporophytic plant, the gametophyte sex differentiation is affected by various environmental factors. Factors studied in recent years include hormones (such as antheridiogen, gibberellic acids (GAs), abscisic acid (ABA) and ethylene), light, population density, nutrition (such as sugar and methionine) and metal ions (such as calcium and cobalt ions) to the fern gametophyte sex differentiation. Results of these physiological researches suggested that: (1) Antheridiogens induce male development and repress female development of the gametophyte, and GAs play a similar function with antheridiogens in sex determination. However, ABA blocks antheridiogen-induced antheridium formation. 1-aminocylopropane-1-carboxylic acid (ACC), the ethylene precursor, can enhance the number of antheridia induced by GA, while an inhibitor of ACC synthesis aminooxyacetic acid (AOA) restrains antheridia formation via inhibition of cell division. (2) Light intensity and quality affect sex expression, while the effect is varies by species. (3) Sugar addition not only promotes male sex expression in young differentiating Equisetum gametophytes, but also accelerates the onset of hermaphroditism in mature females. (4) Calcium is required in blue-light-promoted and red-light-inhibited antheridiogenesis in the fern Anemia phyllitidis. Moreover, increasing methionine concentrations mixed with GA3 enhances the number of precociously formed antheridia, and cobalt ions also stimulate the GA3-induced antheridia formation. (5) Population density also affects gametophyte growth and sexual expression. Female and asexual gametophytes dominated in populations of low and high densities respectively while hermaphroditic and male gametophytes were dominant at intermediate population densities. Furthermore, recent mutant phenotype analysis and molecular biological research revealed that some specific genes, including ANI1, ANI1, HER, TRA, FEM, and MAN, involved in the sex differentiation under the regulation of antheridiogen. This paper gives an overview of ferns sex determination in response to environmental factors and its mechanism.