Pollen transcriptome analysis

Pollen development is an attractive model in which to dissect the cellular networks that control cell growth, division and differentiation. An essential step towards providing a comprehensive understanding of these processes is to define the transcriptional profiles of developing cells.

Together with Dr David Honys (CAS, Prague) we developed procedures to isolate developing microspores and pollen at bicellular, tricellular and mature stages from Arabidopsis. Transcriptome analysis of these cell populations with Affymetrix ATH1 genome arrays identified a total of 13,977 male gametophyte-expressed genes of which 10% were considered male gametophyte-specific (Honys & Twell, 2004).

Our results revealed that the progression from proliferating microspores to terminally differentiated pollen is characterised by large-scale repression of 'early' genes and the activation of a unique 'late' gene expression program in maturing pollen. The expression profiles of numerous and distinct clusters of co-expressed genes were identified that highlight complex gametophytic gene regulatory networks.

This quantum increase in knowledge of gametophytic transcription has informed numerous genome-led studies of the gene networks and cellular functions involved in pollen development. Analysis of the profiles of 1,350 transcription factor genes represented on the ATH1 Gene Array identified 608 (45%) that are expressed in the male gametophyte, including 54 (15.7%) that appear to be male gametophyte-specific. We found clear biases in the representation of large transcription factor families in the male gametophyte compared with the sporophyte and continue to explore the regulation and functional roles of several classes of gametophyte and germline-specific transcription factors.

Reference

Honys D and Twell D (2004) Transcriptome analysis of haploid male gametophyte development in Arabidopsis. Genome Biology, 5:R85

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