CLONING AND FUNCTIONAL CHARACTERISATION OF A PUTATIVE POWDERY MILDEW SUSCEPTIBILITY GENE IN GRAPEVINE
Grapevine is highly susceptible to a range of different fungal pathogens, including powdery mildew (Erysiphe necator), which can cause severe reductions in yield and quality. As part of multifaceted approach to improve the genetic resistance of grapevine to powdery mildew, we are investigating the grapevine pectate lyase-like (PLL) gene family because previous research in Arabidopsis has demonstrated that a specific member of the AtPLL gene family (PMR6) was required for powdery mildew susceptibility. Sixteen VvPLLs were predicted to be present in the grapevine genome. Based on sequence homology, we identified three genes, designated VvPLL1, VvPLL2 and VvPLL3, as potential orthologs of PMR6, and the coding regions were amplified from Vitis vinifera Cabernet Sauvignon. All three VvPLL candidates were found to encode proteins with a C-terminal GPI-anchor, which is a characteristic of PMR6 (AtPLL13) and VvPLL-GFP fusion constructs confirmed they were targeted to the plasma membrane. Quantitative RT-PCR analysis indicated constitutive expression of VvPLL1, VvPLL2 and VvPLL3 in all tissues examined including leaves, roots, flowers and berries. In contrast, other members of the VvPLL gene family such as VvPLL9 and VvPLL10 were tissue-specific (floral). In agreement with observations for PMR6 (AtPLL13), VvPLL1, VvPLL2 and VvPLL3 were not significantly up-regulated by powdery mildew infection. Functional complementation experiments are currently underway in which the three VvPLL genes have been transformed into the Atpmr6 mutant under the control of either the CaMV 35S or Arabidopsis PMR6 promoter. Our ultimate aim is to silence these VvPLL genes in grapevine to determine if we can modify susceptibility to powdery mildew.
Salami, S.A., Ebadi, A., Naghavi, M.R. and Dry, I.B. (2014). CLONING AND FUNCTIONAL CHARACTERISATION OF A PUTATIVE POWDERY MILDEW SUSCEPTIBILITY GENE IN GRAPEVINE. Acta Hortic. 1046, 169-177