Analysis Of Different Transcriptional Responses To Citrus Canker Between Meiwa And Newhall Via Microarray

Citrus canker is one of the main diseases affecting citrus production. In this study, microarray was employed to analyze the differential gene expression patterns of two varieties, Newhall (canker-tolerant) and Kumquat (canker-sensitive), after being inoculated with the canker bacteria. Subsequently, bioinformatics and semi-quantitive RT-PCR were conducted to analyze the results and verify the differentially expressed genes, respectively. The main results are as follows:1. In vitro inoculation test showed that after inoculation of the citrus canker pathogen, typical symptoms appeared within 3-5 days, and the incidence rate was nearly 100% at the fifth day.2. The CEL files of the Affymetrix chips were analyzed independently by RankProd statistical package downloaded from R&bioconductor software platform. Differentially expressed genes were screened under the standard of Fold-Change|>=4 and FDR<=0.5. The results showed that:there are 610 up-regulated and 714 down-regulated genes in Newhall, while 530 and 264 in kumquat respectively. Together, there are 150 up-regulated and 80 down-regulated genes in both varieties. Out of the 150,97 up-regulated genes expression are higher in Kumquat. Five genes are up-regulated in Kumquat but down-regulate in Newhall, and 376 up-regulated genes in Kumquat have no match in Newhall. Taken the 97,5,376 together, these 478 genes were selected for further bioinformatics analysis, such as functional annotation by GO, EC, with Annot8r. The results showed that many of the genes, as reported before, were associated with disease resistance, such as salicylic acid, jasmine acid, flavonoids, HR, SAR, stomatal regulation, hormones transport, ethylene, class-propane, and lignin. In addition, in our study, there are many differently expressed genes whose functions may have roles in Citrus canker resistance, needing to be further researched.3. Seventeen genes were selected for semi-Quantitative RT-PCR, whose expressions were consistent with the results of gene chip, indicating a certain reliability of microarray.