Parallel evolution of TCP and B-class genes in Commelinaceae flower bilateral symmetry

Abstract

BackgroundFlower bilateral symmetry (zygomorphy) has evolved multiple times independently across angiosperms and is correlated with increased pollinator specialization and speciation rates. Functional and expression analyses in distantly related core eudicots and monocots implicate independent recruitment of class II TCP genes in the evolution of flower bilateral symmetry. Furthermore, available evidence suggests that monocot flower bilateral symmetry might also have evolved through changes in B-class homeotic MADS-box gene function.MethodsIn order to test the non-exclusive hypotheses that changes in TCP and B-class gene developmental function underlie flower symmetry evolution in the monocot family Commelinaceae, we compared expression patterns of teosinte branched1 (TB1)-like, DEFICIENS (DEF)-like, and GLOBOSA (GLO)-like genes in morphologically distinct bilaterally symmetrical flowers of Commelina communis and Commelina dianthifolia, and radially symmetrical flowers of Tradescantia pallida.ResultsExpression data demonstrate that TB1-like genes are asymmetrically expressed in tepals of bilaterally symmetrical Commelina, but not radially symmetrical Tradescantia, flowers. Furthermore, DEF-like genes are expressed in showy inner tepals, staminodes and stamens of all three species, but not in the distinct outer tepal-like ventral inner tepals of C. communis.ConclusionsTogether with other studies, these data suggest parallel recruitment of TB1-like genes in the independent evolution of flower bilateral symmetry at early stages of Commelina flower development, and the later stage homeotic transformation of C. communis inner tepals into outer tepals through the loss of DEF-like gene expression.

The Maize PI/GLO Ortholog Zmm16/sterile tassel silky ear1 Interacts with the Zygomorphy and Sex Determination Pathways in Flower Development

“…Furthermore, in maize, B class gene expression is asymmetrically absent from the adaxial domain. Although later stages were examined, a similar B class asymmetry was reported in other monocots Theissen, 2008, 2011;Preston and Hileman, 2012;Hsu et al, 2015). This contrasts with A. majus where the zygomorphy program acts independently (i.e., in parallel) of ABC floral organ patterning (Carpenter and Coen, 1990).…”

“…In the monocots, the role of the CYC-like genes in floral development (if any) remains undefined. In Commelina (Commelinales) and the Zingiberales, there is some evidence for a correlation between CYC-like gene expression and the development of floral zygomorphy (Bartlett and Specht, 2011;Preston and Hileman, 2012). Functional studies of the CYC-like genes in the grasses implicate them in the control of shoot branching (Doebley et al, 1995;Kebrom et al, 2006), inflorescence branch angle and leaf morphology (Bai et al, 2012), and lemma versus palea identity in rice (Yuan et al, 2009), not structural floral zygomorphy.…”

Origin and evolution of petals in angiosperms

“…Asparagus) are derived. Clear support for this has been provided by a study of three species of Commelinaceae by Preston & Hileman (2012). Contrary to the two other species with similar petaloid inner whorl tepals, the inner ventral tepal of Commelina communis is similar to the outer whorl tepals in morphology and absence of B-gene expression.…”

The Tarenaya hassleriana Genome Provides Insight into Reproductive Trait and Genome Evolution of Crucifers

“…Both PI and AP3 in Tarenaya have diverged in expression levels. MADS box B-class gene homologs in the AP3 lineage as well as TCP members have been implicated in the establishment of monosymmetric flowers in monocots, including Orchidaceae species (Tsai et al, 2004(Tsai et al, , 2008Mondragón-Palomino and Theissen, 2009;Bartlett and Specht, 2010;Preston and Hileman, 2012), PI genes have contributed to floral diversification in Asterids (Viaene et al, 2009), and B-class genes have contributed to Aquilegia floral diversification (Kramer et al, 2007). Thus, it is possible that both B-class and TCP genes have an impact on floral monosymmetry in Cleomaceae.…”