Genome-wide transcriptomic analysis of the sporophyte of the moss Physcomitrella patens

Bryophytes are the most basal of the extant land plants. A major feature of these plants is the biphasic alteration of generations between a dominant haploid gametophyte and a minor diploid sporophyte phase. To analyse the differences in the transcriptome of the early gametophyte (protonema) and early and mid-sporophyte phases of the moss Physcomitrella patens, microarray gene expression profiles were performed using dissected sporophyte tissue. Through further analysis the early and mid-sporophyte phases were compared. RNA isolated from the Gametophytic protonemal tissue was hybridised to six microarrays. Each microarray was hybridised with RNA from a separate biological replicate. Three of these microarrays were co-hybridised with RNA isolated from early sporophytes. With the third gametophyte biological replicate and early sporophyte replicate a dye swap was carried out. The remaining three microarrays hybridised with RNA from the gametophytes were co-hybridised with RNA from mid-sporophytic tissue. A dye swap was carried out on the sixth gametophyte replicate and third mid-sporophyte replicate.To meet the quality requirements for the microarray experiment, at least 400 sporophytes were used per extraction. Three or four RNA extracts were then pooled for further precipitation to maximise purity and concentration. Up to 1600 sporophytes were harvested to prepare sufficient RNA for each microarray replicate. In bioinformatic analysis the channels were split into individual channels and the early and mid-sporophyte were compared.