Amy’s project is focused on understanding the regulation of membrane trafficking during pollen tube growth. In plants, root hairs and pollen tubes undergo a highly polarized form of cell expansion termed tip growth. During this process, membranes and cell wall material are added only to the growing tip of the cell. In addition to undergoing polarized growth, root hairs and pollen tubes are accessible for direct observation and as such are used as models for the study of membrane trafficking.
RabGTPases are key regulators of membrane trafficking. Our work has focused on the RabA family of Rab GTPases which are predicted to be localized to the trans-Golgi network (TGN). This family is of particular interest as they have the potential to serve as important regulators during polarized cell growth as cell wall components are predicted to be transported through the TGN.
Previously, we found one member of the RabA family, RabA4b, is tip-localized in growing root hairs (A) and is important for the tip growth that occurs in these cells. Pollen tubes, like root hairs, expand by tip growth. We found that RabA4d, a close relative of RabA4b, is expressed specifically in pollen (B) and is tip-localized in pollen tubes (C). Amy’s project is focused on examining the role of RabA4d in the tip growth of pollen tubes.
A. Root of a seedling stably transformed with EYFP-RabA4b imaged using either transmitted light (brightfield) or epifluorescence with appropriate EYFP filters. Arrowheads indicate root hairs with tip-localized EYFP-RabA4b and arrows indicate root hairs without tip-localized EYFP-RabA4b. B. Total RNA was extracted from the roots (Rt), leaves (Lf), stems (St), flowers (Fl) and pollen (P) of four-week old WT plants. RT-PCR analysis of RabA4 subfamily expression was performed with gene-specific primers with ubiquitin as a loading control. C. Pollen of plants expressing a native promoter EYFP-RabA4d fusion construct was germinated on slides and observed using a Nikon Eclipse using with differential images contrast (DIC) or fluorescence and appropriate EYFP filters.
