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Taking BF gene as one of the candidate genes influencing on reproductive traits in present study, this study used PCR-RFLP analyzised the polymorphism of intron 1 of BF gene in Large White sows. A single nucleotide polymorphism (SNP) named as BF-intron 1-C79T was detected. And the three genotypes of CC, CT, TT got fitted Hardy-Weinberg equilibrium with chi2-fitness test. An association analysis was tested between the genetic polymorphism at intron 1 and total number born (TNB), number born alive (NBA), born weight (BW) and placental efficiency (PE) respectively. It showed that, at first parity, the TNB, NBA, BW and PE with CC genotype were higher than those with CT genotype but not significant (P>0.05). Meanwhile, in multiparous sow population, the TNB, NBA and PE with CC genotype were significantly more than those with TT genotype (P<0.05), with increase of 3.45, 3.92, and 23.80%, respectively. Thus BF-intron 1-C79T is suggested to be a potential genetic marker for the breeding on the reproductive traits and placental efficiency.

The mutant plasmid pAmy413C, in which G takes the place of A at the 271 position of alpha-amylase gene on the pAmy413 from B. licheniformis, was constructed by site-direct mutagenesis. At the N-terminus of the mature alpha-amylase, amino acid +2Asn was substituted by +3Asp in the wild type protein. Then, the alpha-amylase output of the mutant plasmid pAmy413C in B. subtilis was 2.02-2.57 times higher than that of the wild type pAmy413C in the same strain. The amino acid sequencing at the N-terminus of the matural alpha-amylase revealsed that the recognition site of signal peptidase I moved one amino acid upstream, from Ala-(+2)Asn to AlaAla-(+3) Asp. That is, the +2Asn of the wild type was changed to the +3Asp of the mutant. The secondary structural analysis showed that a 14-cycle structure formed in the alpha-amylase mRNA when the free energy was -51.7 kcal. In this case, the mutant is identical with the wild type. The difference between them is that G at 271 position is no longer paired with U at 211 position, hence, a G-overhang is formed. The secondary structural analysis of protein showed that one amino acid diminished in the turn structure of amino acid at 33-37 position, and this very amino acid is involed in an alpha-helix structure. In short, all the changes mentioned above in conformation and charged amino acids contribute to the increase in the protein secretion in B. subtilis.