RESUMO
Using rapid amplification of cDNA ends, a full-length cDNA sequence of a GDP-L-galactose phosphorylase-like gene was isolated from leaves infected by Erysiphe necator in the Chinese wild (Vitis pseudoreticulata) clone, 'Baihe-35-1', an E. necator-resistant genotype. The full-length cDNA, designated as VpVTC, comprised 1943 bp and putatively encodes a 453-amino acid polypeptide containing an HIT motif. The deduced amino acid sequence showed high similarity with that of VTC genes from other plants. The expression of VpVTC, determined by reverse transcriptase-polymerase chain reaction, was induced by E. necator and defense signaling molecules, including salicylic acid, methyl jasmonate, and ethephon, in 'Baihe-35-1', the V. quinquangularis genotype 'Shang-24', and the E. necator-susceptible V. pseudoreticulata genotype, 'Hunan-1'. Transcript levels of VpVTC correlated well with the degree of disease resistance in the 3 genotypes. Maximum induction of VpVTC by E. necator (>7-fold at 96 h post-inoculation) occurred in 'Baihe-35-1', which also showed the fastest response to signaling molecules. Upregulating the expression of VpVTC in 'Baihe-35-1' resulted in a gradual increase in the ascorbic acid concentration of leaves inoculated with E. necator. Furthermore, VpVTC was expressed in leaves, stems, inflorescence, tendrils, and fruit at all developmental stages, with the highest level occurring in fruit 35 days after flowering.