Expression differentiation of CYC-like floral symmetry genes correlated with their protein sequence divergence in Chirita heterotricha (Gesneriaceae)
- 316 Downloads
CYCLOIDIEA (CYC) and its homologues have been studied intensively in the model organism Antirrhinum majus and related species regarding their function in controlling floral dorsoventral (adaxial–abaxial) asymmetry, including aborting the adaxial and lateral stamens. This raises the question whether the same mechanism underlies the great morphological diversity of zygomorphy in angiosperms, especially in Lamiales sensu lato, a major clade predominantly with zygomorphic flowers. To address this, we selected a representative in Gesneriaceae, the sister to the remainder of Lamiales s.l., to isolate CYC homologues and further investigate their expression patterns using locus-specific semiquantitative reverse transcriptase polymerase chain reaction. Our results showed that four CYC homologues in Chirita heterotricha differentiated spatially and temporally in expression, in which ChCYC1D was only expressed in the adaxial regions, and transcripts of ChCYC1C were distributed in both the adaxial and lateral regions, while ChCYC2A and ChCYC2B transcripts were only detected in the young inflorescences. ChCYC1C expression in the lateral regions correlated with abortion of the lateral stamens in C. heterotricha hinted at its gain of function, i.e., expanding from the adaxial to the lateral regions in expression. Correlatively, the protein sequences of ChCYC genes exhibited remarkable divergences, in which some lineage-specific amino acids between GCYC1 and GCYC2 in conserved functional domains and two sublineage-specific motifs between GCYC1C and GCYC1D in GCYC1 genes had further been identified. Our results indicated that ChCYC genes had probably undergone an expressional differentiation and specialization in establishing the floral dorsoventral asymmetry in C. heterotricha responding to different selective pressure after gene duplication.
KeywordsDorsoventral asymmetry CYC-like gene RT-PCR expression differentiation Gesneriaceae Chirita heterotricha
We are grateful to James F. Smith for critical comments and improvements on our manuscript, especially in language editing. We also thank Mr. Chen Yan for assistance in the greenhouse. This research was supported by CAS Grant KSCX2-YW-R-135 and National Natural Science Foundation of China Grant, nos. 30770147, 30121003.
- Burtt BL (1990) Gesneriaceae of the Old World. I. New and little-known species of Cyrtandra from Malesia. Edinburgh J Bot 47:201–233Google Scholar
- Doyle JJ, Doyle JL (1987) A rapid DNA isolation procedure for small quantities of fresh leaf tissue. Phytochem Bull 19:11–15Google Scholar
- Du ZY, Wang YZ (2008) Significance of RT-PCR expression patterns of CYC-like genes in Oreocharis benthamii (Gesneriaceae). Journal of Systematics and Evolution 46:23–31Google Scholar
- Feng XZ, Zhao Z, Tian ZX, Xu SL, Luo YH, Cai ZG, Wang YM, Yang J, Wang Z, Weng L, Chen JH, Zheng LY, Guo XZ, Luo JH, Sato S, Tabata S, Ma W, Cao XL, Hu XH, Sun CR, Luo D (2006) Control of petal shape and floral zygomorphy in Lotus japonicus. Proc Natl Acad Sci USA 103:4970–4975PubMedCrossRefGoogle Scholar
- Li ZY, Wang YZ (2004) Plants of Gesneriaceae in China. Henan Science and Technology publishing house, Zhengzhou, ChinaGoogle Scholar
- Möller M, Clokie M, Cubas P, Cronk QCB (1999) Integrating molecular phylogenies and developmental genetics: a Gesneriaceae case study. In: Hollingsworth PM, Bateman RM, Gornall RJ (eds) Molecular systematics and plant evolution. Taylor and Francis, London, pp 375–402Google Scholar
- Ohno S (1970) Euolution by gene duplication. Springer, New YorkGoogle Scholar
- Swofford DL (2002) PAUP*. Phylogenetic Analysis Using Parsimony software (*and other methods) version 4.0b10. Available at: http://paup.csit.fsu.edu/
- Weber A (2004) Gesneriaceae. In: Kubitzki K, Kadereit JW (eds) The families and genera of vascular plants. Springer, Berlin, pp 63–158Google Scholar