title: A PR-4 gene identified from Malus domestica is involved in the defense responses against Botryosphaeria dothidea.
abstract: Pathogenesis-related protein-4 (PR-4) family is a group of proteins with a Barwin domain in C-terminus and generally thought to be involved in plant defense responses. However, their detailed roles are poorly understood in defense of apple plant against pathogenic infection. In the present study, a new PR-4 gene (designated as MdPR-4) was identified from Malus domestica, and its roles in defense responses of apple were investigated. The open reading frame of MdPR-4 gene is of 447 bp encoding a protein of 148 amino acids with a Barwin domain in C-terminus and a signal peptide of 26 amino acids in N-terminus. Sequence and structural analysis indicated that MdPR-4 protein belongs to class II of PR-4 family. The high-level expression of MdPR-4 was observed in flowers and leaves as revealed by quantitative real time PCR. The temporal expression analysis demonstrated that MdPR-4 expression could be up-regulated by Botryosphaeria dothidea infection and salicylic acid (SA) or methyl jasmonate (MeJA) treatment, but suppressed by diethyldithiocarbamic acid (DIECA). In vitro assays, recombinant MdPR-4 protein exhibited ribonuclease activity specific for single strand RNA and significant inhibition to hyphal growth of three apple pathogenic fungi B. dothidea, Valsa ceratosperma and Glomerella cingulata. Moreover, the inhibition was reduced by the presence of 5'-ADP. Taken all together, the results indicate that MdPR-4 protein is involved in the defense responses of apple against pathogenic attack by directly inhibiting hyphal growth, and the inhibition is correlated with its ribonuclease activity, where as MdPR-4 expression is regulated by both SA and JA signaling pathway.
authors.affiliation: College of Life Science, Qingdao Agricultural University, Qingdao 266109, China; College of Horticulture, Qingdao Agricultural University, 700 Changcheng Road, Qingdao 266109, China.
authors.forename: Suhua
authors.initials: S
authors.lastname: Bai
authors.forename: Chaohua
authors.initials: C
authors.lastname: Dong
authors.forename: Baohua
authors.initials: B
authors.lastname: Li
authors.forename: Hongyi
authors.initials: H
authors.lastname: Dai
mesh_terms: D000085:Acetates / Q000378:metabolism; D001203:Ascomycota / Q000235:genetics / Q000378:metabolism*; D003517:Cyclopentanes / Q000378:metabolism; D060467:Disease Resistance / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D025301:Hyphae / Q000235:genetics / Q000378:metabolism; D027845:Malus / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D054883:Oxylipins / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics
chemical_list: D000085:Acetates; D003517:Cyclopentanes; D054883:Oxylipins; D010940:Plant Proteins; C072239:methyl jasmonate; D020156:Salicylic Acid