Grape apoplasmic β-1,3-glucanase confers fungal disease resistance in Arabidopsis

• VvGHF17 was detected in the culture medium by grape cell cultures.
• VvGHF17 is apoplasmic β-1,3-glucanase.
• VvGHF17 inhibits fungal infection but not bacterial infection in Arabidopsis.
• VvGHF17 may be a candidate for the transgene to create transgenic grapevines.

To identify apoplasmic proteins in grape cells, we investigated proteins secreted into grape cell culture medium and detected β-1,3-glucanase VvGHF17 in the medium. VvGHF17 is expressed constitutively in grape leaves and berry pulp and skin. Experiments using VvGHF17:GFP fusion protein demonstrated that VvGHF17 is localized at the apoplasmic space of cells, suggesting that VvGHF17 is apoplasmic β-1,3-glucanase. To understand how VvGHF17 protects grapevine against phytopathogens, we created Arabidopsis transgenic plants expressing VvGHF17. VvGHF17-expressing Arabidopsis plants exhibited disease resistance to both Botrytis cinerea and Colletotrichum higginsianum, but not to Pseudomonas syringae pv. tomato DC3000. The inhibitory effect of VvGHF17 to the infection by the fungi was promoted when VvGHF17 protein was expressed in large amounts in the plants. In conclusion, apoplasmic VvGHF17 may be a candidate for the transgene to create transgenic grapevines that are robust to multiple fungal attacks.