|Holmes Davis, Rachel|
Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2005
Publication Date: 7/29/2005
Citation: Engel, M.L., Holmes-Davis, R.A., McCormick, S. 2005. Green Sperm: Identification of Male Gamete Promoters in Arabidopsis thaliana. Plant Physiology. 138:2124-2133. Interpretive Summary: We used a maize expressed sequence tag library to identify genes that were potentially expressed in sperm. We then found their closest sequence matches in Arabidopsis, and tested whether the Arabidopsis gene control regions (so-called promoters) would direct sperm-specific expression of reporter genes. We found two promoters that did; these promoters are therefore useful tools with which to study genes that are expressed in sperm cells.
Technical Abstract: Previously, in an effort to better understand the male contribution to fertilization, we completed a maize (Zea mays) sperm expressed sequence tag project. Here, we used this resource to identify promoters that would direct gene expression in sperm cells. We used reverse transcription-polymerase chain reaction to identify probable sperm-specific transcripts in maize and then identified their best sequence matches in the Arabidopsis (Arabidopsis thaliana) genome. We tested five different Arabidopsis promoters for cell specificity, using an enhanced green fluorescent protein reporter gene. In pollen, the AtGEX1 (At5g55490) promoter is active in the sperm cells and not in the progenitor generative cell or in the vegetative cell, but it is also active in ovules, roots, and guard cells. The AtGEX2 (At5g49150) promoter is active only in the sperm cells and in the progenitor generative cell, but not in the vegetative cell or in other tissues. A third promoter, AtVEX1(At5g62580), was active in the vegetative cell during the later stages of pollen development; the other promoters tested (At1g66770 and At1g73350) did not function in pollen. Comparisons among GEX1 and GEX2 homologs from maize, rice (Oryza sativa), Arabidopsis, and poplar (Populus trichocarpa) revealed a core binding site for Dof transcription factors. The AtGEX1 and AtGEX2 promoters will be useful for manipulating gene expression in sperm cells, for localization and functional analyses of sperm proteins, and for imaging of sperm dynamics as they are transported in the pollen tube to the embryo sac.