Patterns of gene duplication and functional diversification during the evolution of the AP1/SQUA subfamily of plant MADS-box genes.
Members of the AP1/SQUA subfamily of plant MADS-box genes play broad roles in the regulation of reproductive meristems, the specification of sepal and petal identities, and the development of leaves and fruits. It has been shown that AP1/SQUA-like genes are angiosperm-specific, and have experienced several major duplication events. However, the evolutionary history of this subfamily is still uncertain. Here, we report the isolation of 14 new AP1/SQUA-like genes from seven early-diverging eudicots and the identification of 11 previously uncharacterized ESTs and genomic sequences from public databases. Sequence comparisons of these and other published sequences reveal a conserved C-terminal region, the FUL motif, in addition to the known euAP1/paleoAP1 motif, in AP1/SQUA-like proteins. Phylogenetic analyses further suggest that there are three major lineages (euAP1, euFUL, and AGL79) in core eudicots, likely resulting from two close duplication events that predated the divergence of core eudicots. Among the three lineages, euFUL is structurally very similar to FUL-like genes from early-diverging eudicots and basal angiosperms, whereas euAP1 might have originally been generated through a 1-bp deletion in the exon 8 of an ancestral euFUL- or FUL-like gene. Because euFUL- and FUL-like genes usually have broad expression patterns, we speculate that AP1/SQUA-like genes initially had broad functions. Based on these observations, the evolutionary fates of duplicate genes and the contributions of the frameshift mutation and alternative splicing to functional diversity are discussed.
Shan
Hongyan
H
State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Xiangshan, Beijing, People's Republic of China.
Zhang
Ning
N
Liu
Cuijing
C
Xu
Guixia
G
Zhang
Jian
J
Chen
Zhiduan
Z
Kong
Hongzhi
H
D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D019143:Evolution, Molecular; D016368:Frameshift Mutation; D020440:Gene Duplication; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D026161:MADS Domain Proteins / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology
D026161:MADS Domain Proteins; D010940:Plant Proteins; D014157:Transcription Factors