Preliminary research on genes and proteins related to a spontaneous mutant of <i>Citrus reticulata</

Bud mutations of citrus happen frequently and are the main natural resource for new cultivars. ‘Mingliutianju’ (Citrus reticulata ‘Mingliutianju’, MP) is a novel late ripening, very productive mandarin cultivar selected from‘Chuntianju’ (C. reticulata ‘Chuntianju’, CP) through spontaneous bud mutation. In addition, the cultivar ismorphologically contrast to the smooth fruit of its parent ‘Chuntianju’ by having prominent vertical narrowstrips on its fruit surface. Large-scale analysis of gene expression differences between peels of MP and CP wasperformed at the 12th week and the 23rd week post flowering using Affymetrix GeneChip? citrus genome array. Altogether, 395 differentially expressed genes, including 132 up-regulated and 263 down-regulated genes, wereidentified in the mutant. Singular Enrichment Analysis (SEA) and Parametric Analysis of Gene Set Enrichment(PAGE) were performed and 7 statistically significantly differential-expressed genes were selected for furtherstudies. Results from semiquantitative RT-PCR performed on these 7 genes were generally correlated with thoseobserved with the microarray. These seven genes include three UDP-glucosyltransferase genes, two diseaseresistance-responsive protein-related genes, one chitinase gene and one protein kinase gene. Thirty threedifferentially expressed proteins were identified by two-dimensional gel electrophoresis using the same material. The differential proteins included 17 up-regulated and 16 down-regulated in the mutant. Pathway identificationwas conducted on these 33 differential expressed proteins through the web-based platform KOBAS. When theseKEGG pathways were arranged according to their P values, flavonol biosynthetic process pathway ranked first.