风信子器官发生定向控制系统中生殖器官发育机理的研究

Floral organs have been successfully induced from the regenerated floral buds of Hyacinthus orientalis L. by precisely controlling exogenous hormones in the medium. Under high concentrations of cytokinin and auxin, the regenerated floral bud produces only tepals. However, at reduced levels of the hormones, the regenerated floral bud can produce stamens and/or carpels with ovules. To understand the molecular mechanism of hormone-regulated flower development, a few genes including HAG1, HOM1, HPI1 and HAP2 have been isolated from the floral tissues of Hyacinthus. Overexpression of HAG1 in Arabidopsis created flower phenotypes resembling those of the apetala2 mutant and AG transgenic Arabidopsis plants. Furthermore, HAG1 expression pattern was similar to that of AG, confirming that HAG1 is the ortholog of AG in Hyacinthus. HAG1 mRNA was first detected in cultured explants at day 5 in the medium containing high level cytokinin and auxin, which could induce floral regeneration in vitro. However, no HAG1 mRNA was detected in the cultured explants until day 10 in media with low or no hormones. Overexpressed HOM1 initiated ovule formation on the edge of sepals in Arabidopsis indicating that it determines ovule identity. HOM1 RNA was only detectable in the ovaries and ovules in the plant. Interestingly, in vitro its RNA could not be detectable in the sepals of regenerated flowers under high concentration of hormones, however, its RNA was detected at reduced level hormones which could induce ovule differentiation in the regenerated flower. HPI1 and HAP2 expressive levels have no change during flower regeneration. Besides, we have isolated lots of cDNA sequences by cDNA array screening, and their expression and function analysis is in progress. Our data support the hypothesis that the hormone-regulated HAG1 and HOM1 activities are required for the induction of floral bud and the determination of floral organ types during the regeneration of floral buds

本项目以风信子生殖器官发生定向控制系统为主要实验系统，分离控制器官发生的同源异形基因、分析其在不为条件下的表达方式。在此基础上，进一步分离调节同源异形基因表达的上游基因，并探讨其调节机理。该研究对于认识同源异形基因的表达受内外因子的调节，这一重要理论问题将有独到的贡献。