Development of cDNA normalization system and preliminary transcription analysis of KCS genes in apple tissues

Abstract

Wax production is an important aspect of apple (Malus domestica Borkh.) fruit development from both theoretical and practical point of views. The complex molecular mechanism that controls wax biosynthesis is still widely unknown but many studies focused on this topic. We aimed to develop further the experimental framework of these efforts with a description of an improved reference genes expression system. Results in the literature show that similarities exist among the expression of some housekeeping genes of different plant species. Based on these considerations and on gene expression data from Arabidopsis thaliana, some genes in apple were assigned for analysis. EST sequences of apple were used to design specific primers for RT-PCR experiments. Isolation of intact RNA from different apple tissues and performing RT-PCR reaction were also key point in obtaining expression patterns. To monitor DNA contamination of the RNA samples, specific primers were used that amplify intron-containing sequences from the cDNA. We found that actin primers can be used for the detection of intron containing genomic DNA, and tubulin primers are good internal controls in RT-PCR experiments. We were able to make a difference between tissue-specific and tissue-independent gene-expression, furthermore we found tissue specific differences between the expression patterns of candidate genes, that are potentially involved in wax-biosynthesis. Our results show that KCS1 and KCS4 are overexpressed in the skin tissue, this could mean that these genes have skin-specific expression in apple fruit.