Original Paper

Molecular Genetics and Genomics

, Volume 284, Issue 2, pp 105-119

First online:

The actin multigene family in Populus: organization, expression and phylogenetic analysis

  • Deqiang ZhangAffiliated withNational Engineering Laboratory for Tree Breeding, Beijing Forestry UniversityKey Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, Beijing Forestry University Email author 
  • , Qingzhang DuAffiliated withNational Engineering Laboratory for Tree Breeding, Beijing Forestry UniversityKey Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, Beijing Forestry University
  • , Baohua XuAffiliated withNational Engineering Laboratory for Tree Breeding, Beijing Forestry UniversityKey Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, Beijing Forestry University
  • , Zhiyi ZhangAffiliated withNational Engineering Laboratory for Tree Breeding, Beijing Forestry UniversityKey Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, Beijing Forestry University
  • , Bailian LiAffiliated withNational Engineering Laboratory for Tree Breeding, Beijing Forestry UniversityKey Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, Beijing Forestry University Email author 

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Abstract

Despite the significance of actin in plant growth and development, little is known of the structure, expression and evolution of the actin gene family in woody plants. In this study, we systematically examined the diversification of the actin gene family in Populus by integrating genomic organization, expression, and phylogeny data. Genome-wide analysis of the Populus genome indicated that actin is a multigene family consisting of eight members, all predicted to encode 377-amino acid polypeptides that share high sequence homology ranging from 94.2 to 100% identity. Microarray and real-time PCR expression analysis showed that the PtrACT family members are differentially expressed in different tissues, exhibiting overlapping and unique expression patterns. Of particular interest, all PtrACT genes have been found to be preferentially expressed in the stem phloem and xylem, suggesting that poplar PtrACTs are involved in the wood formation. Gene structural and phylogenetic analyses revealed that the PtrACT family is composed of two main subgroups that share an ancient common ancestor. Extremely high intraspecies synonymous nucleotide diversity of πsyn = 0.01205 was detected, and the πnon-synsyn ratio was significantly less than 1; therefore, the PtACT1 appears to be evolving in Populus, primarily under purifying selection. We demonstrated that the actin gene family in Populus is divided into two distinct subgroups, suggesting functional divergence. The results reported here will be useful in conducting future functional genomics studies to understand the detailed function of actin genes in tree growth and development.

Keywords

Actin genes Gene structure Phylogeny Differential expression Nucleotide diversity Poplar