Pollination

Ramin Yadegari, PhD, is interested in understanding the gene-regulatory processes that mediate fertilization and initiation of seed development. The plant life cycle alternates between a diploid sporophyte generation and a haploid gametophyte generation. The angiosperm female gametophyte is critical to the reproductive process. It is the structure within which egg cell production and fertilization take place. Using the model plant Arabidopsis thaliana, Dr. Yadegari and his lab are focusing on two specific processes: 1) development of the female gametophyte and 2) control of seed initiation by gene-regulatory complexes before and after fertilization. For example, they use a combination of expression-based analyses and genetic resources of Arabidopsis to identify major gene-regulatory networks involved in differentiation of the female gametophyte cell types. Similarly, using biochemical, molecular and genetic approaches, they identify components of the Polycomb-group complexes that mediate epigenetic repression of gene expression before fertilization.

Ravishankar Palanivelu, PhD, possesses a long-term goal to understand the molecular basis of how cells communicate with each other. His lab employs pollen tube guidance during Arabidopsis thaliana reproduction as a model system to achieve this goal. Currently, the focus remains to understand the molecular mechanisms that underlie pollen tube functions in A. thaliana.A pollen tube's journey to an egg cell within the pistil involves a series of cell-cell interactions such as attraction, repulsion and adhesion (Illustration 1, mov file). While these processes are likely mediated by several guidance signals, only a handful of guidance signals produced by female tissues have been identified. The guidance of pollen tubes into the ovule micropyle is highly reproducible, resembling the polarized migration of axons, yet sharing few genes in common. Dr. Palanivelu’s lab is undertaking a multidisciplinary approach - Genetics, Cell Biology and Biochemistry - to understand the molecular mechanisms that underlie pollen tube functions in A. thaliana. Characterization of pollen tube guidance in A. thaliana holds enormous potential as it focuses on a process that is: 1) very unique to plants, 2) poorly understood at the molecular level, 3) amenable to genetic, cell biological and biochemical techniques, and 4) a rapid way to identify novel plant signals that allow communication between cells possible despite their thick extracellular walls. Additionally, we have recently developed an in vitro pollen tube guidance assay in A. thaliana that monitors both attractive and repulsive interactions between pollen tubes and ovules, processes normally difficult to discern by virtue of them occurring within opaque pistils. These attributes therefore make pollen tube guidance in A. thaliana an ideal model system to study cell-cell interaction in plants.