Plant actin was a kind of constitutive expression protein existed broadly, and had high conservatism (Meagher et al., 1999). Since Yan and Shi put forward that actin existed in higher plant for the first time in 1963(Yan and Shi, 1963), at present, actin had been discovered in pollen, root hair, stem cambium layer, stem phloem, vagina cell, leaf epidermal cell, tendril and endocarp tissues of higher plant (Kost et al., 1999), and also was multi-gene family like as that of animal and fungi (Zhang and Liu, 2006; Hussey et al., 2006). Plant actin involved in cell microfilaments formation, whereas, microfilaments were key components of cytoskeleton and participated in important physiological activities such as intracellular cytoplasmic streaming, keep of configuration, movement, division, differentiated, transport of substance, signal transduction and polarity constructing etc. (Ma et al., 2010). As house-keeping gene, Actin can express relative stably to some extent in tissues and cells and had many advantages such as constitutive expression, multiplication easily. Hence, like as other house-keeping genes included GAPDH, 18SrRNA, TBP and β-2-microglobulin, Actin often was used as inner reference in quantitative or semiquantitative PCR reaction to revise expression amount of target genes (Zhu et al., 2006; Yang et al., 2007; Liu, 2003). 

Guzmania, belonged to Bromeliaceae, was native to tropics and suibtropics of American, and was superior quality potted flower plant in flower marketplace. At present, there was a lack of information in public about Guzmania Actin gene. Based on full length cDNA library constructed successfully in Guzmania ostara and plenty of EST sequences information were obtained by sequencing randomly on a large scale formerly, full length cDNA sequence of Actin gene was obtained, by Primer Walking sequencing to EST monoclones belonged to Actin gene. Finally, there was a bioinformatics analysis in-depth to the gene. The research laid a foundation to construction of quantitative and semiquantitative PCR technique in ornamental Bromeliaceae.

1 Results and Analysis
1.1 Cloning of Goactin1 gene
Through primer walking sequencing to EST monoclone: |ppfca0_001242.z1.scf|, which belonged to Actin gene, a 1 625 bp full length cDNA sequence was obtained, and named for Goactin1 (GenBank accession number: HQ184438). It had a 1 131 bp ORF (open reading frame) which encoded 377 amino acids (Figure 1). 

Figure 1 mRNA sequence and deduced amino acid sequence of Goactin1 gene

1.2 Blast analysis of full length cDNA and putative amino acid sequence
Nucleotide-nucleotide blast analysis showed the full length cDNA sequence of Goactin1 gene had a very high homologue to Actin gene of Populus trichocarpa, Vigna radiata, Betula luminifera, Oryza sativa, Zea mays, Arabidopsis thaliana, Nicotiana tabacum, Gossypium hirsutum, Pisum sativum, Ricinus communis, Pyrus communis, Aegiceras corniculatum, Prunus salicina, Phaseolus vulgaris, Phalaenopsis sp, Picea abies, Larix gmelinii, Mimosa pudica, Diospyros kaki, Plantago major, Linum usitatissimum and Solanum tuberosum. And the homologue of Populus trichocarpa (XM_002311131, GENE: 7467546), Vigna radiata(AF143208.1) and Betula luminifera (FJ410442.1) was the highest, which reached 84 percent. Moreover, by comparing the deduced amino acid sequences (BlastP) with the protein data bank, the result showed that Goactin1 also had very high homologue to actin protein of many other species in the data bank. The maximum number of amino acid homologue was 99 percent  from Ricinus communis(XP_002530711.1, EEF31665.1), Solanum tuberosum (CAA39280.1), Gossypium hirsutum (AAC31886.1), Populus trichocarpa (XP_002308365.1, XP_002322664.1, ABK92789.1, XP_002311167.1, EEE88534.1, XP_002316289.1, ABK92513.1, EEF02460.1), Caragana Korshinskii (ACK87035.1) and Nicotiana tabacum (ACH69153.1, CAA45149.1).

Figure 2 Secondary structure of putative Goactin1 protein

 

Figure 3 Conservative domain of Goactin1 amino acid sequence

 

Figure 4 Tertiary structure of putative Goactin1 protein based on A chain of 2BTF

Based on multisequencing comparison between Goactin 1 and actin amino acid sequence of other species by ClustalX (1.81) program, circular molecular phylogenetic tree was established use MEGA 4.0 program (Neighbor Joining method). Analytical result was showed at figure 5. With Solanum tuberosum (gi|231503|, gi|231496|), Gossypium hirsutum (gi|54035683|), Nicotiana tabacum (gi|197322805|, gi|461465|), Brachypodium sylvaticum (gi|226858185|), Arabidopsis thaliana (gi|15231447|, gi|15238387|, gi|28393806|), Goactin1 were gathered to the same group.

Figure 5 Molecular evolution analyses in putative amino acid sequence of Goactin1

2 Discussion