Journal de pathologie végétale et de microbiologie

Abstrait

Increased Expression of the Tomato SISWEET15 Gene During Grey Mold Infection and the Possible Involvement of the Sugar Efflux to Apoplasm in the Disease Susceptibility

Yuichiro Asai, Yuhko Kobayashi and Issei Kobayashi

Host plant susceptibility genes, which facilitate pathogen growth during plant infection, are attractive targets for disease-resistance breeding. To explore candidate susceptibility genes in tomatoes during Botrytis cinerea infection, the fungal infection-responsive SWEET genes were screened for out of all 31 tomato SlSWEET genes. The expression of only one gene, SlSWEET15, was induced by B. cinerea at the pre-necrotic stage (16 h post inoculation), whereas most of the other SWEET genes were downregulated. The expression of the SlSWEET15 transiently increased by 16 h post inoculation, then reduced to basal levels by 24 h post inoculation. We measured the glucose and sucrose contents of

fluid of infected cotyledons at the pre-necrotic stage (20 h post inoculation). The sugar contents of the apoplasmic fluids were significantly higher in the infected cotyledons compared to 0 h. Furthermore, glucose and sucrose can promote growth and invasion of B. cinerea both in vitro and in vivo. SWEET proteins in clade III, including the deduced SlSWEET15, are well-known sugar efflux transporters. These results suggest that SlSWEET15 is induced by B. cinerea and that this is exploited by the fungus, which may provide sugars to promote hyphal growth in the pre-necrotic stage of infection in tomato.