Cloning, Expression And Single Nucleotide Polymorphisms Analysis Of Cellulose Synthase Gene (PtoCesA4) In Populus Tomentosa

The cellulose synthase gene (CesA) plays a key role in regulation of biosynthetic cellulose during the wood formation. In this study, a full-length cDNA clone encoding PtoCesA4 was isolated from the cDNA prepared from immature xylem zone of Populus tomentosa by the approach of biological informatics and RT-PCR method. The cDNA is 3 757 bp in length with an open reading frame (ORF) which is capable of encoding a protein of 1042 AA. The deduced protein sequence of the PtoCesA4 shared 80.3%,78.9% and 75.6% identity with Arabidopsis thaliana AtCesA4, Oryza sativa OsCesAl and Pinus taeda PtCesA2, respectively. Tissue differential expression with Realtime-PCR indicated that PtoCesA4 have their mRNA products in root, stem, leave and apical shoot meristems, but have some differences in them. The PtoCesA4 have the most abundant mRNA products in mature leaf, immature and mature xylem, with medium expression in root and apical shoot meristems, with some expression in the bark and phloem, but a lowest abundance was detected in cambium. The genomic sequences of PtoCesA4 in 40 individuals were aligned, compared and analyzed using the software MEGA4.0.2 and DnaSP5.10.01. A total of 153 single nucleotide polymorphisms (SNPs) were detected and the frequency and diversity of SNPs are 1/35 bp and 0.005 02, respectively. In which,51 of 153 are common SNPs and 102 are rare SNPs. There are 118 and 35 mutation types of transition and transversion, respectively. In total,69 SNPs were detected in the coding regions of PtoCesA4 of which 59 are silent mutations and 10 are missense mutations. The linkage disequilibrium of SNPs in the PtoCesA4 was analyzed and the result showed that LD declines rapidly within the gene regions of PtoCesA4. It suggested that in Populus genome wide LD mapping may not be feasible and necessary, but LD mapping based on PtoCesA4 gene could be particularly useful in breeding programs of forest tress. The results, therefore, provided the important foundation for association genetics of PtoCesA4 gene and gene-assisted breeding of new germplasms with desirable wood fiber traits in P. tomentosa.