Evolution of bract development and B-class MADS box gene expression in petaloid bracts of Cornus s. l. (Cornaceae)

• Published in: The New phytologist 2012-10, Vol.196 (2), p.631-643
• Main Authors: Feng, Chun‐Miao, Liu, Xiang, Yu, Yi, Xie, Deyu, Franks, Robert G., Xiang, Qiu‐Yun (Jenny)
• Format: Article
• Language: English
• Subjects: APETALA3; Biological Evolution; Bracts; B‐class gene expression; Cell Shape; Cornaceae; Cornaceae - anatomy & histology; Cornaceae - genetics; Cornaceae - growth & development; Cornaceae - ultrastructure; Cornus; Cornus canadensis; Cornus florida; development; Developmental biology; Divergence; Epidermal cells; Evolution; evolution of petaloid bracts; Evo‐Devo; Flowers; Flowers - cytology; Flowers - genetics; Flowers - growth & development; Flowers - ultrastructure; Gene expression; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; Gene families; Genes; Genes, Plant - genetics; heterotopic petaloidy; Inflorescence - growth & development; Inflorescences; MADS box proteins; MADS Domain Proteins - genetics; MADS Domain Proteins - metabolism; Meristems; Molecular modelling; Morphology; Petals; Phylogeny; PISTILLATA; Plant Epidermis - cytology; Plant Epidermis - ultrastructure; Plant Leaves - cytology; Plant Leaves - genetics; Plant Leaves - growth & development; Plant Leaves - ultrastructure; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Progressions; Seasons; Time Factors
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2012.04255.x

Despite increasing interest in the molecular mechanisms of floral diversity, few studies have investigated the developmental and genetic bases of petaloid bracts. This study examined morphological patterns of bract initiation and expression patterns of B-class MADS-box genes in bracts of several Cornus species. We suggest that petaloid bracts in this genus may not share a single evolutionary origin. Developmental pathways of bracts and spatiotemporal expression of B-class genes in bracts and flowers were examined for four closely related dogwood species. Divergent morphological progressions and gene expression patterns were found in the two sister lineages with petaloid bracts, represented by Cornus florida and Cornus canadensis. Phylogeny-based analysis identified developmental and gene expression changes that are correlated with the evolution of petaloid bracts in C. florida and C. canadensis. Our data support the existence of independent evolutionary origins of petaloid bracts in C. canadensis and C. florida. Additionally, we suggest that functional transference within B-class gene families may have contributed to the origin of bract petaloidy in C. florida. However, the underlying mechanisms of petaloid bract development likely differ between C. florida and C. canadensis. In the future this hypothesis can be tested by functional analyses of Cornus B-class genes.