Evolution of theSPATULA/ALCATRAZgene lineage and expression analyses in the basal eudicot,Bocconia frutescensL. (Papaveraceae).
BACKGROUND
SPATULA(SPT) andALCATRAZ(ALC) are recent paralogs that belong to the large bHLH transcription factor family. Orthologs of these genes have been found in all core eudicots, whereas pre-duplication genes, namedpaleoSPATULA/ALCATRAZ, have been found in basal eudicots, monocots, basal angiosperms and gymnosperms. Nevertheless, functional studies have only been performed inArabidopsis thaliana, whereSPTandALCare partially redundant in carpel and valve margin development andALChas a unique role in the dehiscence zone. Further analyses of pre-duplication genes are necessary to assess the functional evolution of this gene lineage.


RESULTS
We isolated additionalpaleoSPT/ALCgenes fromAristolochia fimbriata,Bocconia frutescens,Cattleya trianaeandHypoxis decumbensfrom our transcriptome libraries and performed phylogenetic analyses. We identified the previously described bHLH domain in all analyzed sequences and also new conserved motifs using the MEME suite. Finally, we analyzed the expression of threepaleoSPT/ALCgenes (BofrSPT1/2/3) fromBocconia frutescens, a basal eudicot in the Papaveraceae. To determine the developmental stages at which these genes were expressed, pre- and post-anthesis carpels and fruits ofB. frutescenswere collected, sectioned, stained, and examined using light microscopy. Using in situ hybridization we detected thatBofrSPT1/2/3genes are expressed in floral buds, early sepal initiation, stamens and carpel primordia and later during fruit development in the dehiscence zone of the opercular fruit.


CONCLUSIONS
Our expression results, in comparison with those available for core eudicots, suggest conserved roles of members of theSPT/ALCgene lineage across eudicots in the specification of carpel margins and the dehiscence zone of the mature fruits. Although there is some redundancy betweenALCandSPT, these gene clades seem to have undergone some degree of sub-functionalization in the core eudicots, likely by changes in cis regulatory regions and to some extent in coding sequences, at least in Brassicaceae. Our results also indicate that inBocconia frutescens, paleoSPT/ALCgenes may play a role in early floral organ specification that was subsequently lost in core eudicot lineages.
Instituto de Biología, Universidad de Antioquia, Medellín, 1226, Colombia.|New York Botanical Garden, Bronx, NY 10458 USA.|City University of New York, New York, NY 10016 USA.
Cecilia
C
Zumajo-Cardona
New York Botanical Garden, Bronx, NY 10458 USA.
Barbara Ann
BA
Ambrose
Instituto de Biología, Universidad de Antioquia, Medellín, 1226, Colombia.
Natalia
0000-0003-3528-8078
N
Pabón-Mora
ALCATRAZ; Basal eudicots; Bocconia frutescens; Fruit development; Papaveraceae; SPATULA; paleoSPT/ALC