Genome-wide identification and comprehensive expression analysis of VviASN and VviGS gene families during seed development/abortion in grapevine

Asparagine synthetase (ASN) and glutamine synthetase (GS) play important roles in nitrogen metabolism and recycling in plants. In this study, we performed the characterization and expression analysis of the ASN and GS gene families in grape. It contains two ASN genes, VviASN1 and VviASN2, and five GS genes, VviGS1.1, VviGS1.2, VviGS1.3, VviGS2a and VviGS2b. For each gene, full-length complementary DNAs were cloned and the properties of encoded protein were predicted using bioinformatics approaches. Real-time PCR analysis showed that the transcript levels of VviASN1, VviASN2, VviGS1.1, VviGS1.2 and VviGS2b during ovule (seed) development were higher in seedless cultivars than in seeded. It was showed that asparagine (Asn) content in the seeds of seedless grapes was higher than in seeded, while glutamine (Gln) content was higher in seeded. Levels of both amino acids increased during early seed development, then decreased as development progressed. Based on correlation between amino acid content and gene expression, VviASN1 may play a major role in the synthesis of Asn in grape seeds. VviASN1 and VviASN2 were highly expressed in flower and leaf, respectively. VviGS1.1, VviGS2a and VviGS2b were highly expressed in leaf, while VviGS1.2 was highly expressed in root. In summary, our findings suggest novel roles for the VviASN and VviGS genes families during seed development/abortion in grapevine.