Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2008
Publication Date: 7/30/2008
Citation: Borges, F., Gomes, G., Gardner, R., Moreno, N., McCormick, S.M., Feijo, J., Becker, J. 2008. Comparative Transcriptomics of Arabidopsis thaliana Sperm Cells. Plant Physiology. 10.1104/pp.108.125229.
Interpretive Summary: We purified sperm cells from Arabidopsis plants. We isolated RNA from these sperm cells and determined which genes in the genome are expressed in sperm. We found sperm express many genes, and that the proteins encoded by these genes encompass many different categories. This data can now be used as a starting point to discover the roles of these sperm-expressed proteins.
Technical Abstract: In flowering plants the two sperm cells are embedded within the cytoplasm of the growing pollen tube and as such are passively transported to the embryo sac, wherein double fertilization occurs upon their release. Understanding the mechanisms and conditions by which male gametes mature and take part in fertilization are crucial goals in the study of plant reproduction. Studies of gene expression in male gametes of maize and Plumbago, and in lily generative cells already showed that the previously held view of transcriptionally inert male gametes was not true, but genome-wide studies were lacking. Analyses in the model plant Arabidopsis thaliana were hindered because no method to isolate sperm cells was available. Here we used Fluorescence-activated cell sorting (FACS) to isolate sperm cells from Arabidopsis, allowing GeneChip analysis of the transcriptome of sperm cells at a genome-wide level. Comparative analysis of the sperm cell transcriptome with those of representative sporophytic tissues and of pollen showed that sperm has a distinct and diverse transcriptional profile. Functional classifications of genes with enriched expression in sperm cells showed that DNA repair, ubiquitin-mediated proteolysis and cell cycle progression are over-represented Gene Ontology categories. Moreover, analysis of the small RNA and DNA methylation pathways suggests that distinct mechanisms might be involved in regulating the epigenetic state of the paternal genome. We identified numerous candidate genes whose involvement in sperm cell development and fertilization can now be directly tested in Arabidopsis. These results provide a roadmap to decipher the role of sperm-expressed proteins.