A fern WUSCHEL-RELATED HOMEOBOX gene functions in both gametophyte and sporophyte generations

BackgroundPost-embryonic growth of land plants originates from meristems. Genetic networks in meristems maintain the stem cells and direct acquisition of cell fates. WUSCHEL-RELATED HOMEOBOX (WOX) transcription factors involved in meristem networks have only been functionally characterized in two evolutionarily distant taxa, mosses and seed plants. This report characterizes aWOXgene in a fern, which is located phylogenetically between the two taxa.ResultsCrWOXBtranscripts were detected in proliferating tissues, including gametophyte and sporophyte meristems ofCeratopteris richardii. In addition,CrWOXBis expressed in archegonia but not the antheridia of gametophytes. Suppression ofCrWOXBexpression in wild-type RN3 plants by RNAi produced abnormal morphologies of gametophytes and sporophytes. The gametophytes of RNAi lines produced fewer cells, and fewer female gametes compared to wild-type. In the sporophyte generation, RNAi lines produced fewer leaves, pinnae, roots and lateral roots compared to wild-type sporophytes.ConclusionsOur results suggest thatCrWOXBfunctions to promote cell divisions and organ development in the gametophyte and sporophyte generations, respectively. CrWOXBis the first intermediate-clade WOX gene shown to function in both generations in land plants.