Epigenetics and reproductive development in Arabidopsis

During reproductive development, meiosis produces gametes with reduced ploidy that will fuse to produce the zygote and restore ploidy levels. Here, I will illustrate the impact of epigenetic mechanisms on two key reproductive processes, maternal control of embryogenesis, and meiosis, using Arabidopsis as a model.
In animals, maternally provided transcripts control key early steps of embryogenesis such as embryo polarity, before the zygotic genome is active. In plants, the extent of maternal control over embryogenesis remains unclear. To address this issue, I characterized a new maternal effect mutant of Arabidopsis, and uncovered a link between DNA demethylation, required for establishment of genomic imprinting in female gametes, and DNA repair.
In plants, meiosis produces haploid spores that undergo gametogenesis. DUET, which encodes a PHD finger protein, is expressed in male meiosis and is essential for fertility. The loss of DUET results in unique meiotic defects, but DUET function is unknown. I report that DUET localizes to chromosomes during meiotic prophase. Analysis of DUET PHD finger revealed that it can bind H3K4me2 in vitro, and is essential for function.  Furthermore, I report that DUET is required for chromosome segregation and cytokinesis, and that both phenotypes originate from microtubule defects. Finally, I found that DUET was required for expression of a subset of late meiotic genes, including JASON, a gene required for meiotic spindle organization. These results suggest that epigenetic control of gene expression during meiosis is critical for male reproductive development in Arabidopsis.