Molecular and genetic mechanisms regulating sperm cell development in Arabidopsis thaliana

Sexual reproduction in flowering plants involves the production of male and female gametes crucial for successful fertilisation, yet molecular mechanisms in these processes are largely unknown. The goal of the research presented in this thesis is to understand more about these mechanisms. A novel pollen division mutant, duo pollen 4 (duo4), that fails to produce twin sperm cells was investigated. Genetic analyses revealed that duo4 acts post-meiotically and does not affect female gametophyte development. The majority of duo4 germ cells complete DNA replication and fail to enter mitosis, but mutant germ cell appears to differentiate normally when crossed to different cell fate markers. Map-based cloning defined the DUO4 locus to a 14.5 kb region containing the Cdh1/Fzr/Ste9- related, APC activator gene, CCS52A1. Molecular genetic approaches were combined to identify the cause of the germline defects in duo4. Gene expression analysis, misexpression and RNA interference (RNAi) experiments indicate that the duo4 phenotype results from misexpression of CCS52A1 in the male germline. This is persuasive evidence that CCS52 activity is subject to tight control during male germ cell cycle progression. DUO1 is a major transcription regulator of germ cell division and differentiation and the second major objective describes the validation of four native target genes in the DUO1 regulatory network. These target genes encode metabolic and transport-related proteins. The activity of these promoters was shown to be DUO1-dependent in the male gametophyte or the male germline, highlighting the importance of the DUO1 regulon in a range of functions required for sperm cell development. Collectively, these results advance understanding of how the male gametes are produced, and provide an improved molecular understanding of reproduction in higher plants.EThOS - Electronic Theses Online ServiceGBUnited Kingdo