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.