Stepwise evolution of corolla symmetry in CYCLOIDEA2-like and RADIALIS-like gene expression patterns in Lamiales.
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OBJECTIVE
CYCLOIDEA2 (CYC2)-like and RADIALIS (RAD)-like genes are needed for the normal development of corolla bilateral symmetry in Antirrhinum majus L. (snapdragon, Plantaginaceae, Lamiales). However, if and how changes in expression of CYC2-like and RAD-like genes correlate with the origin of corolla bilateral symmetry early in Lamiales remains largely unknown. The asymmetrical expression of CYC2-like and/or RAD-like genes during floral meristem development could be ancestral or derived in Plantaginaceae.•


METHODS
We used in situ RNA localization to examine the expression of CYC2-like and RAD-like genes in two early-diverging Lamiales.•


RESULTS
CYC2-like and RAD-like genes are expressed broadly in the floral meristems in early-diverging Lamiales with radially symmetrical corollas, in contrast to their restricted expression in adaxial/lateral regions in core Lamiales. The expression pattern of CYC2-like genes has evolved in stepwise fashion, in that CYC2-like genes are likely expressed briefly in the floral meristem during flower development in sampled Oleaceae; prolonged expression of CYC2-like genes in petals originated in the common ancestor of Tetrachondraceae and core Lamiales, and asymmetrical expression in adaxial/lateral petals appeared later, in the common ancestor of the core Lamiales. Likewise, expression of RAD-like genes in petals appeared in early-diverging Lamiales or earlier; asymmetrical expression in adaxial/lateral petals then appeared in core Lamiales.•


CONCLUSIONS
These data plus published reports of CYC2-like and RAD-like genes show that asymmetrical expression of these two genes is likely derived and correlates with the origins of corolla bilateral symmetry.
Department of Biology, The University of Missouri - St. Louis, One University Boulevard, St. Louis, Missouri 63121 USA.
Jinshun
J
Zhong
Department of Biology, The University of Missouri - St. Louis, One University Boulevard, St. Louis, Missouri 63121 USA.
Elizabeth A
EA
Kellogg
D005075:Biological Evolution; D035264:Flowers / Q000235:genetics / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D000068378:Lamiales / Q000145:classification* / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism
D010940:Plant Proteins
Antirrhinum majus; CYC2-like gene; Lamiales; Plantaginaceae; RAD-like gene; corolla symmetry; snapdragon