Genomic expression profiling of mature soybean (Glycine max) pollen.
BACKGROUND
Pollen, 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.


RESULTS
Compared 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.


CONCLUSIONS
This 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.
Haerizadeh
Farzad
F
ARC Centre of Excellence for Integrative Legume Research, Faculty of Land and Food Resources, The University of Melbourne, Parkville 3010, Australia. Farzad.Haerizadeh@codexis.com
Wong
Chui E
CE
Bhalla
Prem L
PL
Gresshoff
Peter M
PM
Singh
Mohan B
MB
D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018745:Genome, Plant; D006360:Heat-Shock Proteins / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000235:genetics; D011058:Pollen / Q000235:genetics*; D018749:RNA, Plant / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D013025:Glycine max / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D025801:Ubiquitin / Q000235:genetics; D015854:Up-Regulation
D006360:Heat-Shock Proteins; D010940:Plant Proteins; D018749:RNA, Plant; D014157:Transcription Factors; D025801:Ubiquitin