Clone of homologous PGIP genes and analysis of the polymorphism of nucleotide sequence in alfalfa

Polygalacturonase-inhibiting proteins(PGIP)are one of the most important defensive proteins, and the understanding of the nucleotide sequences of PGIP genes is the premise and basis of the molecular genetics and molecular biology. This study aimed to isolate the genomic coding sequences of PGIP genes in alfalfa(Medicago sativa)by a homology-based method. Consequently, the part genomic coding sequences of 7 PGIP genes were cloned, and each of these 7 alfalfa PGIP genes had a corresponding homologous PGIP gene from M. truncatula, and they were named as MsPGIP5, MsPGIP6, MsPGIP7, MsPGIP8, MsPGIP9, MsPGIP10 and MsPGIP11. Of the found 7 alfalfa PGIP genes, MsPGIP5, MsPGIP6, MsPGIP8, MsPGIP9 and MsPGIP11 possessed a divergent average inter-SNP distance with a value of 20, 74, 34, 423 and 21 bp, respectively. FPCR-SSCP analysis was performed for MsPGIP5, MsPGIP6, MsPGIP8 and MsPGIP11, and the results showed that a trend of the ratios between their SSCP allele numbers and their PCR fragment sizes, with a value of 20, 56, 22 and 19 bp, respectively, and they were basically consistent with those of their average inter-SNP distances. In contrast, of the found 7 alfalfa PGIP genes, the sequence of MsPGIP9 was highly conserved while MsPGIP5 and MsPGIP11 displayed a large sequence variation, and MsPGIP6 and MsPGIP8 had a median sequence variation.