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Genetic analysis of the DAZ1 transcription factor in Arabidopsis thaliana

The aim of this research was to advance understanding of the molecular and genetic mechanisms by which the transcription factor, DAZ1 (DUO1-ACTIVATED ZINC FINGER 1) supports male germline development in Arabidopsis thaliana. The main approach was to analyse the importance of different protein domains in DAZ1 for generative cell division and pollen fertility. The DAZ1 basic region (BR), the DAZ1 conserved region (CR) and the role of individual zinc finger (ZnF) motifs were investigated. In planta complementation of mutant Arabidopsis daz1-/- daz2+/- plants with deletion and substitution variants of DAZ1 revealed important functional roles for the BR, CR and for ZnF3 in male germline development. DAZ1 variants with BR or CR mutations showed a significant but limited ability to rescue male germ cell division and transmission of daz1 daz2 pollen. A second objective was to study the cause of unexpected seed abortion observed in daz1-/- daz2-/- mutants that express DAZ1 variants with reduced function. Observations revealed ovule enlargement without development of embryo or endosperm tissues indicating early post-fertilisation defects arising from defective gametes. In a third objective, a genetic screen was conducted in Arabidopsis for suppressors of reduced fertility in chemically mutagenised plants expressing a C-terminally truncated DAZ1. Several suppressor lines were identified which were stably maintained through multiple generations. Overall, these studies uncover the importance of protein domains which support the role of DAZ1 in male germline development. This work also generated putative genetic suppressors which could provide access to novel regulators that orchestrate germ cell division and sperm differentiation in Arabidopsis.