SHOOTMERISTEMLESS (STM) encodes a member of the class I KNOX homeodomain protein family that is required for meristem development and maintenance. We have isolated both genomic and cDNA clones of STM from the perennial weed leafy spurge. A comparison to other class I KNOX genes indicates that EeSTM represents an orthologue of AtSTM and not one of the other class I KNOX gene family members. 5′ rapid amplification of cDNA ends (RACE) indicated that the transcription initiation site is close to the start of translation and is conserved between arabidopsis and leafy spurge. Putative cis-acting elements were identified in the EeSTM promoter, including a tuber-specific sucrose-responsive element, which could play a major role in the expression of EeSTM in root tissue.

We developed two leafy spurge bacterial artificial chromosome (BAC) libraries that together represent approximately 5× coverage of the leafy spurge genome. The BAC libraries have an average insert size of approximately 143 kb, and copies of the library and filters for hybridization-based screening are publicly available through the Arizona Genomics Institute. These libraries were used to clone full-length genomic copies of an AP2/ERF transcription factor of the A4 subfamily of DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEINS (DREB) known to be differentially expressed in crown buds of leafy spurge during endodormancy, a DORMANCY ASSOCIATED MADS-BOX (DAM) gene, and several FLOWERING LOCUS T (FT) genes. Sequencing of these BAC clones revealed the presence of multiple FT genes in leafy spurge. Sequencing also provided evidence that two different DAM transcripts expressed in crown buds of leafy spurge during endo- and eco-dormancy result from alternate splicing of a single DAM gene. Sequence data from the FT promoters was used to identify several conserved elements previously recognized in Arabidopsis, as well as potential novel transcription factor binding sites that may regulate FT. These leafy spurge BAC libraries represent a new genomics-based tool that complements existing genomics resources for the study of plant growth and development in this model perennial weed. Furthermore, phylogenetic footprinting using genes identified with this resource demonstrate the usefulness of studying weedy species to further our general knowledge of agriculturally important genes.