Black spot disease in poplar is a disease of the leaf caused by fungus. The major pathogen is Marssonina brunnea f. sp. multigermtubi. To date, little is known about the molecular mechanism of poplar （M. brunnea） interaction. In order to identify the proteins related to disease resistance and understand its molecular basis, the clone ＂NL895＂ （P. euramericana CL＂NL895＂）, which is highly resistant to M. brunnea f. sp. multigermtubi, was used in this study. We used two-dimensional gel electrophoresis （2-DE） and mass spectrometry （MS） to identify the proteins in poplar leaves that were differentially expressed in response to black spot disease pathogen, M. brunnea f. sp. multigermtubi. Proteins extracted from poplar leaves at 0, 12, 24, 48, and 72 h after pathogen-inoculation were separated by 2-DE, About 500 reproducible protein spots were detected, of which 40 protein spots displayed differential expression in levels and were subjected to Matrix assisted laser desorption/ionization time of flight mass spectrometry （MALDI-TOF MS） followed by database searching. According to the function, the identified proteins were sorted into five categories, that is, protein synthesis, metabolism, defense response and unclassified proteins.
Kun YuanBo ZhangYanmei ZhangQiang ChengMingxiu WangMinren Huang
A total of 1,160 differentially expressed genes induced by Marssonina brunnea f. sp. muhigermtubi were identified in Populus deltoides cv. ＇Lux＇ （1-69/55） 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.
