Function and Chromosomal Localization of Differentially Expressed Genes Induced by Marssonina brunnea f. sp. multigermtubi in Populus deltoides

A total of 1,160 differentially expressed genes induced by Marssonina brunnea f. sp. multigermtubi were identified in Populus deltoides cv. ‘Lux’ (I-69/55) with two-colour cDNA microarray including 2,952 cDNAs from two cDNA libraries constructed with 72 h inoculated poplar leaves. Functional analysis showed that 1,160 genes were classified into 11 functional categories that are involved in metabolism (15.9%), signal transduction (9.5%), transcription and replication (8.7%), and cell rescue and defense (7.8%). Among them, 926 genes were sporadically localized on 19 linkage groups. Chromosome 2 contained 102 (11%) differentially expressed genes, followed by chromosome 1 which contains 93 genes (10%), and chromosome 17 had the least number of differentially expressed genes. Clustering of expressed sequence tags (ESTs) in poplar genome was observed at the terminal regions of several chromosomes. The relationship between cluster of genes and plant defense response would be further studied.