Expression profiling of galactinol synthase genes in Coffea arabica L. in response to Hemileia vastatrix infection

Galactinol synthase (GolS: EC 2.4.1.123) is an enzyme that plays crucial roles in various plant species under different stress conditions. Few studies have evaluated the expression of the galactinol synthase (GolS) gene under biotic stress conditions. Here, we report the transcriptional profiles of galactinol synthase genes (CaGolS) and RFOs (raffinose family of oligosaccharides) abundance in two contrasting cultivars of Coffea arabica L. (IAPAR59, resistant and Catuaí Vermelho IAC 99, susceptible) infected with Hemileia vastatrix (coffee leaf rust), one of the most destructive fungal diseases in coffee crops worldwide. RT-qPCR results showed distinct transcriptional regulation of three CaGolS genes in leaves infected with H. vastatrix race II at 0, 12, 24 and 48 h postinoculation. CaGolS1 was upregulated (12 and 24 h) in response to the pathogen infection in the susceptible genotype, while CaGolS2 was downregulated in both genotypes at all sampling times, notably in the susceptible one. CaGolS3 showed a very weak expression level in the leaves of the susceptible genotype. The findings of this study justify further research into the association of RFOs with the response of Arabica coffee plants to H. vastatrix infection using a large panel of resistant and susceptible genotypes.