Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 3/30/2014
Publication Date: 6/24/2014
Citation: Shin, S.B., Fazio, G., Mazzola, M., Zhu, Y. 2014. Isolation and characterization of apple Pythium ultimum response genes and their ethylene and jasmonate mediated transcriptional regulation. Proceedings of 7th International Rosaceae Genomics Conference. 12.
Technical Abstract: Apple Replant Disease (ARD) causes a serious economic loss for the apple industry. Although it has been known that a complex of necrotrophic fungi and oomycetes are the primary causal agents of ARD, the molecular response in apple to infection by these pathogens has not previously been examined. In this study, we identified apple genes that are activated by Pythium ultimum, an oomycete that is a significant component of the ARD pathogen complex. The apple genes examined in this study include those involved in ethylene (ET) biosynthesis and jasmonic acid (JA) biosynthesis, a transcription factor gene that functions as an ET/JA signal integrator (MdERF: ethylene response factor) and a pathogenesis-related (PR) gene that is a target of ERF (MdCHIB: CHITINASEB or '-chitinase). Using real-time quantitative reverse transcription PCR, target gene expression was shown to a 10-60 fold up-regulation in apple root stock seedlings 1-2 days post P. ultimum inoculation. Transcriptional regulation of these target genes by exogenous application of ethylene and jasmonate was also examined. MdERF was not only up-regulated by either ethylene or JA, but the enhanced expression of MdERF was significantly greater when exposed to the combination of these hormones. For MdACS and MdAOS, ethylene and JA serve as a positive or negative regulator depending upon gene isoform and the plant tissues in which expression is monitored. Our data demonstrate that ET/JA cross-talk plays an important role in the apple rootstock response to infection by P. ultimum.