Abstract
BackgroundPollen, the male partner in the reproduction of flowering plants, comprises either two or three cells at maturity. The current knowledge of the pollen transcriptome is limited to the model plant systems Arabidopsis thaliana and Oryza sativa which have tri-cellular pollen grains at maturity. Comparative studies on pollen of other genera, particularly crop plants, are needed to understand the pollen gene networks that are subject to functional and evolutionary conservation. In this study, we used the Affymetrix Soybean GeneChip® to perform transcriptional profiling on mature bi-cellular soybean pollen.ResultsCompared to the sporophyte transcriptome, the soybean pollen transcriptome revealed a restricted and unique repertoire of genes, with a significantly greater proportion of specifically expressed genes than is found in the sporophyte tissue. Comparative analysis shows that, among the 37,500 soybean transcripts addressed in this study, 10,299 transcripts (27.46%) are expressed in pollen. Of the pollen-expressed sequences, about 9,489 (92.13%) are also expressed in sporophytic tissues, and 810 (7.87%) are selectively expressed in pollen. Overall, the soybean pollen transcriptome shows an enrichment of transcription factors (mostly zinc finger family proteins), signal recognition receptors, transporters, heat shock-related proteins and members of the ubiquitin proteasome proteolytic pathway.ConclusionThis is the first report of a soybean pollen transcriptional profile. These data extend our current knowledge regarding regulatory pathways that govern the gene regulation and development of pollen. A comparison between transcription factors up-regulated in soybean and those in Arabidopsis revealed some divergence in the numbers and kinds of regulatory proteins expressed in both species.
Highlights
Pollen, the male partner in the reproduction of flowering plants, comprises either two or three cells at maturity
Detection of differentially expressed transcripts in soybean mature pollen Using the soybean GeneChip®, we compared the transcript profiles of soybean pollen with that of sporophytic tissues consisting of an equal mix of RNA derived from
Functional categories of transcripts differentially expressed in pollen The transcripts represented by the soybean GeneChip® have been annoated as described in Materials and Methods
Summary
The male partner in the reproduction of flowering plants, comprises either two or three cells at maturity. We used the Affymetrix Soybean GeneChip® to perform transcriptional profiling on mature bi-cellular soybean pollen. The meiotic division of diploid sporogenous cells gives rise to a tetrad of haploid microspores. The microspores undergo an asymmetric mitotic division, giving rise to a smaller generative cell enveloped within a larger vegetative cell [1]. The pollen is bicellular at anther dehiscence, with the division of generative cells taking place during pollen tube growth in the female tissues. In some cases such as crucifers and grasses, this division takes place while the pollen is still undergoing maturation in the anther
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