HpaXm from Xanthomonas citri subsp. malvacearum is a novel harpin with two heptads for hypersensitive response.
A novel harpin-like protein, HpaXm, was described from cotton leaf blight bacteria, Xanthomonas. citri subsp. malvacearum. The hpaXm was found to be localized between hrp2 and hrcC. A phylogenetic analysis of the complete amino acid sequence or solely the 13 highly conserved residues H2N-SEKQLDQLLTQLI-COOH in the N-terminal alpha-helix indicates that HpaXm is evolutionarily closer to HpaGXag and HpaXac than to Hpa1Xoo and Hpa1Xoc. A synthesized peptide containing two heptads, 39-LDQLLTQ-LIMALLQ-52, from the N-terminal alpha-helical region of HpaXm displayed a comparable activity in inducing HR, but other two synthesized derivatives, HpaXmDeltaT44C and HpaXmDeltaM48Q showed a reduced activity of HR. The data from a GST trap test revealed that HpaXm was released into the extracellular medium, hpaXm mutant deficient for the leader peptide (1-MNSLNTQIGANSSFL-15) was unable to be secreted outside cells but still induced HR in tobacco leaves.
Department of Plant Pathology, Nanjing Agricultural University, Nanjing, China.
Wei-Guo
WG
Miao
Cong-Feng
CF
Song
Yu
Y
Wang
Jin-Sheng
JS
Wang
D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D003368:Gossypium / Q000382:microbiology; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D018515:Plant Leaves / Q000276:immunology / Q000382:microbiology; D017434:Protein Structure, Tertiary; D014026:Nicotiana / Q000276:immunology / Q000382:microbiology; D014974:Xanthomonas / Q000737:chemistry / Q000235:genetics / Q000276:immunology*
D001425:Bacterial Outer Membrane Proteins; C075462:harpin protein, Erwinia amylovora