As we can see in Figure 2 and Supplementary Table SII, there are at least 17 GST genes in common carp which have undergone gene duplication, including classes of MGST1, GSTK, GSTM, GSTA and GSTT.
For instance, MGST1.1b was universally expressed in all tissues, while its duplicate copy, MGST1.1a, was absent in gill, liver and muscle.
The alignment of multiple peptides of MGST1 was created with the ClustalW multiple sequences alignment program, displayed using the BOXSHADE 3.21 program (http://www.ch.embnet.org) and used to construct the phylogenetic tree using the neighbor-joining methods of MEGA software version 3.0 (Kumar et al., 2004).
The mRNA levels of Chicken MGST1 were measured using the Quant SYBR Green PCR Kit (Tiangen, Beijing, China) and the ABI PRISM 7900 Sequence Detection System (Applied Biosystems).
The fragments of 721 bp for MGST1 were generated by 3'-RACE and 393 or 381 bp by 5'-RACE.
The MGST1 peptide was predicted to have an isoelectric point of 9.67 and a molecular weight of 17.24 kDa by using the Compute pI/Mw tool (http://ca.expasy.
nlm.nih.gov/blast/) revealed that the identities and positives of amino acid sequence were 69 and 80%, 69 and 80%, 67 and 80%, 67 and 81%, 43 and 59%, 42 and 58% when Dwarf Brown chicken MGST1 peptide was compared with rat, mouse, cow, human, drosophila-ra and drosophila-rb, respectively.
KKXX-like motif, KALY, a probable ER (endoplasmic reticulum) Membrane Retention Signal, was found in the C-terminus of Chicken MGST1 peptides.
The 12 bp deletion/ insertion polymorphism was not found in genomic DNA (data not shown), which indicated that the 12 nt deletion-insertion in chicken MGST1 mRNA was not due to the mutation of DNA and it must have resulted from other factors.
In further study, it would be interesting to determine if the 12 nt deletion/ insertion polymorphism in the 5' UTR of the MGST1 gene functions similarly.
Construction of phylogenetic tree of the orthologous peptides for the MGST1
A phylogenetic tree of the orthologous peptides for MGST1 was constructed based on their homology in amino acid sequence using two kinds of drosophila MGST1 as the outgroup (Figure 5).