AbstractsBiology & Animal Science

Unique to the lifecycle of plant is the existence of a multicellular haploid gametophyte generation. Elucidation of the genetic makeup of gametophyte development and function is important for several reasons. This phase of the plant lifecycle is still poorly understood and difficult to examine. The strategy used in this thesis was the analysis of mutants created by the two-element Ac/Ds transposon system that displayed segregation distortion of a selectable marker. Four of the mutant isolated had a reduced transmission through both male and female gametophytes verified by reciprocal crosses. Both the 5 end and 3 ends of the transposon were identified and characterised in all four mutant lines. Only one mutant line, dsg 3127, resulted in the identification a single gene involved in gametophyte and embryo development,which encodes a WD-40 repeat protein (WDR). The other mutant lines showed deletions or rearrangements. Phenotype examination of dsg 3127 showed an arrest in pollen development at the binucleate to trinucleate stage Furthermore, embryo development arrested at various stages from the zygote stage to the early globular stage. Alleles of dsg3127 were investigated and an embryo phenotype could be found in one of the mutant alleles. Both Real-time RT PCR and reporter gene constructs showed an expression of the gene during embryo sac development, early embryo development and at early stages of pollen development. in silico analysis of the genes promoter was performed to compliment the reporter gene construct as well as give a hint as to the function. Several BELLRINGER (BELL1-like homeobox protein) binding sites were identified, thus indicating regulation of the gene by BELL1 or BELL1-like protein. Further bioinformatics analyses showed that the gene is conserved across species and is therefore likely to be part of a basic cellular mechanism required for gametophyte- and seed development.