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Scientia Silvae Sinicae ›› 2013, Vol. 49 ›› Issue (11): 67-76.doi: 10.11707/j.1001-7488.20131109

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Isolation, Expression, and Association Genetics of the S-Adenosyl-L-Homocysteine Hydrolase Gene A (PtSAHHA) in Populus tomentosa

Gong Chenrui, Wang Lu, Du Qingzhang, Zhang Deqiang   

  1. 1. Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants of Ministry of Education National Engineering Laboratory for Tree Breeding Beijing Forestry University Beijing 100083
  • Received:2013-06-06 Revised:2013-08-21 Online:2013-11-25 Published:2013-11-26

Abstract:

In this study, a full-length cDNA clone encoding PtSAHHA was isolated from the cDNA library prepared from mature xylem zone of Populus tomentosa by the bioinformatics and molecular biology. The PtSAHHA cDNA had 1 935 bp length with a corresponding open reading frame (ORF) of 1 458 bp that could encode a protein of 485 amino acids. Tissue-specific expression analysis indicated that the PtSAHHA transcripts were the most abundant mRNA products in stem xylem, intermediate in stem cambium and mature leaf, and the lowest abundant in young leaf. By aligning,comparing and analyzing the genomic sequences of PtSAHHA in 45 random individuals of P.tomentosa with the software of MEGA5.0 and DnaSP5, a total of 166 single nucleotide polymorphisms (SNPs) were detected, with the SNP frequency of 1/15 bp and the diversity (πT) of 0.010 58. There were 88 SNPs detected in the coding regions of PtSAHHA, of which 34 were synonymous nucleotide substitutions, and 53 were missense mutations and 1 was nonsense mutation. The diversity level of synonymous nucleotide substitutions (πSynonymous=0.024 91) was tenfold of nonsynonymous nucleotide substitutions (πNonsynonymous=0.002 33), suggesting that the gene might be evolved under purifying selection at the synonoymous sites of the coding region in P. tomentosa. Linkage disequilibrium test in the PtSAHHA showed that LD declined rapidly within the regions of PtSAHHA with the length increase to 800 bp(r2 < 0.1). On this basis, candidate gene-based association analysis of 42 common single-SNPs (frequency > 10%) with six wood traits in an association population of 426 unrelated individuals showed 3 SNPs that were significantly associated with 3 wood traits, respectively. This study provides an important genetic foundation for molecular marker-assisted selection breeding programs with the goals of improving the quality and quantity of wood products of P. tomentosa.

Key words: Populus tomentosa, S-adenosyl-L-homocysteine hydrolase (SAHH), single nucleotide polymorphisms, linkage disequilibrium (LD), wood property

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