Search for: All records

Flowers are a key reproductive innovation of the angiosperms. Seed plant reproductive axes (including flowers) evolved as reproductively specialized shoots of the land plant diploid sporophyte, with the gamete-producing haploid gametophyte becoming reduced and enclosed within ovules and microsporangia. The transcription factor LEAFY (LFY) initiates floral development, yet it predates flowers and is found across all land plants. LFY function outside angiosperms is known from the moss Physcomitrium patens, where it controls the first cell division of the sporophyte, and from the model fern Ceratopteris richardii, a seedless vascular plant where CrLFY1 and CrLFY2 maintain vegetative meristem activity. However, how LFY’s floral role evolved remains unclear. Using over-expression, we uncover new roles for CrLFY1/2 in fern gametophyte reproduction, in sperm cells and in the gametophyte's multicellular notch meristem. While no sporophytic reproductive function was detected in terms of time to sporing, over-expression supports a role in frond compounding and in the zygote's first cell division. Our findings suggest a potentially ancestral LFY function in fern haploid-stage reproduction, which might have been co-opted into the sporophyte during the origin of the flower. 

PremiseMultiple transitions from insect to wind pollination are associated with polyploidy and unisexual flowers inThalictrum(Ranunculaceae), yet the underlying genetics remains unknown. We generated a draft genome ofThalictrum thalictroides, a representative of a clade with ancestral floral traits (diploid, hermaphrodite, and insect pollinated) and a model for functional studies. Floral transcriptomes ofT. thalictroidesand of wind‐pollinated, andromonoeciousT. hernandeziiare presented as a resource to facilitate candidate gene discovery in flowers with different sexual and pollination systems. MethodsA draft genome ofT. thalictroidesand two floral transcriptomes ofT. thalictroidesandT. hernandeziiwere obtained from HiSeq 2000 Illumina sequencing and de novo assembly. ResultsTheT. thalictroidesde novo draft genome assembly consisted of 44,860 contigs (N50 = 12,761 bp, 243 Mbp total length) and contained 84.5% conserved embryophyte single‐copy genes. Floral transcriptomes contained representatives of most eukaryotic core genes, and most of their genes formed orthogroups. DiscussionTo validate the utility of these resources, potential candidate genes were identified for the different floral morphologies using stepwise data set comparisons. Single‐copy gene analysis and simple sequence repeat markers were also generated as a resource for population‐level and phylogenetic studies.