|Norelli, John (jay) - Jay|
Submitted to: Plant Molecular Biology Reporter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2013
Publication Date: 2/10/2014
Citation: Villanova, L., Wisniewski, M.E., Norelli, J.L., Vinas, I., Torres, R., Usall, J., Phillips, J.G., Droby, S., Teixido, N. 2014. Transcriptomic profiling of apple in response to inoculation with a pathogen (P. expansum) and a non-pathogen (P. digitatum). Plant Molecular Biology Reporter. 32:566-582. Interpretive Summary: Understanding the molecular regulation of disease resistance and susceptibility is fundamental to developing new approaches to disease control. Using genome wide assays of gene expression to understand the response of plants to biotic and abiotic stress is a critical objective of NP-301, Plant Genetic Resources, Genomics and Genetic Improvement. Global studies of gene expression in plants provide an opportunity to study changes in hundreds of genes simultaneously. This is accomplished by attaching thousands of genes onto a glass slide known as a microarray and probing the slide with samples of DNA obtained from the plant of interest. Using this technique, one can study a plant’s response to biotic or abiotic stress and also identify pathways responsible for important traits such disease resistance. This research utilized an apple microarray containing approximately 40,000 apple gene sequences to study the response of immature and mature harvested apple fruit to inoculation with either a pathogen (Penicillium expnasum) or a non-pathogen (Penicillium digitatum). Results indicated that fruit inoculated with a pathogen express genes related to defense and those that are involved in ameliorating oxidative stress. In contrast, the non-pathogen induced expression of genes related to the formation of lignin and other secondary metabolites. This suggests that the pathogen somehow interferes with the formation of compounds that could block spread of the pathogen into healthy, non-wounded tissues. This information will be used to identify specific genes responsible for resistance to the postharvest pathogen, Penicillium expansum, in resistant genotypes and wild species of apple.
Technical Abstract: Penicillium expansum, the causal agent of blue mould of pome fruits, is a major postharvest pathogen in all producing countries. To develop a better understanding of disease resistance mechanisms in apples, a comprehensive transcriptional analysis of apple gene expression in response to a compatible (P. expansum) and non-host (P. digitatum) pathogen was conducted using an apple microarray of approximately 40,000 probes. The resulting data provide further evidence that apples inoculated with P. expansum exhibit significant up-regulation of defense-related genes and genes involved in ROS detoxification. In contrast, apples inoculated with P. digitatum, a non-host pathogen, exhibited up-regulation of genes involved in phenylpropanoid metabolism. To confirm the accuracy of the expression profiles obtained with the microarray, RT-qPCR was conducted for four genes specifically in the the pheynylpropanoid pathway. Expression data was obtained for different time points and fruit maturity stages. The highest expression level of the phenylpropanoid genes was detected 48 h after inoculation with P. expansum in both immature and mature apples. These results support the hypothesis that apples respond in a complex and diverse manner to the compatible compared to the non-host pathogen. To the best of our knowledge, this is the first study in apple fruit that has conducted an analysis of global changes in gene expression in response to a compatible (P. expansum) and non-host (P. digitatum) pathogen.