Full transcriptome analysis of huanglongbing (HLB)-infected 'Valencia' sweet orange (Citrus sinensis).

摘要

HLB is a threat to the survival of the citrus industry because of its destructive nature and unavailability of any type of control for the disease. Florida has been devastated with major economic losses that HLB has brought forth on the crop since its detection in 2005, which can cause the same devastating results to the Texas industry since its detection and confirmation in January 2012 in a sweet orange (Citrus sinensis) orchard in San Juan, TX. It is of great importance to identify molecular ways with which citrus plants trigger disease resistance when these are challenged by abiotic or biotic stress. In this study we focus on early host responses by identifying differential gene expression in healthy and HLB infected sweet orange ( C. sinensis) leaves using RNA sequencing (RNA-Seq). Data analyses indicate that of a total of 20 million reads, 6606 genes were differentially expressed in new flush infected leaves when compared to healthy control leaves. Quantitative real time PCR (qRT-PCR) analysis of 20 randomly chosen genes (10 up and 10 down regulated) was performed to validate RNA-Seq results of gene expression. Results revealed that of the 20 genes selected, 19 correspond with the RNA-Seq results. Alternative splicing events in infected leaves had a dramatic increase when compared to healthy leaves. Furthermore, qRT-PCR revealed variation in expression of calcium channel genes at different stages of HLB infected leaves when compared to healthy controls. Findings from these analyses are crucial in order to understand how HLB affects homeostasis and general gene expression in citrus, which may be a tool to understand disease resistance, identify genes of importance for future genetic transformations targeting resistance to biotic and abiotic stress, and to allow the designing of disease management tools.