The infiltration efficiency of Agrobacterium-mediated transient transformation in four apple cultivars

Abstract

Studies of gene function in apple fruits (Malus domestica) have been hindered by the long juvenile period of apple fruit trees. Transient gene expression is a relatively simple method for gene functional analyses, and has been broadly applied to several plant species; however, few studies have reported a method for systematic transient expression in apple fruits. Here, we developed a highly efficient and robust Agrobacterium-mediated transient expression system for apple fruit, which allows rapid analysis of diverse gene functions. Using a β-glucuronidase gene (GUS) as a reporter for Agrobacterium-mediated transformation, we found that the most suitable infiltration pressure for gene function assays in ‘Red Fuji’, ‘Granny Smith’ and ‘Royal Gala’ fruits was −90 kPa, but −70 kPa in ‘Golden Delicious’. The infiltration efficiency of ‘Golden Delicious’ was higher than that of the other apple cultivars. Transient silencing of MdMYB10, an anthocyanin biosynthesis regulator, altered anthocyanin content in ‘Red Fuji’, demonstrating that vacuum infiltration with Agrobacterium can be used for gene functional analysis. Also a significant positive correlation was found between microcrack density and infiltration efficiency. We conclude that this method represents a general tool for efficient and targeted transient regulation of gene expression in apple fruits.