title: Domain dissection of AvrRxo1 for suppressor, avirulence and cytotoxicity functions.
abstract: AvrRxo1, a type III effector from Xanthomonas oryzae pv. oryzicola (Xoc) which causes bacterial leaf streak (BLS) in rice, can be recognised by non-host resistance protein Rxo1. It triggers a hypersensitive response (HR) in maize. Little is known regarding the virulence function of AvrRxo1. In this study, we determined that AvrRxo1 is able to suppress the HR caused by the non-host resistance recognition of Xanthomonas oryzae pv. oryzae (Xoo) by Nicotiana benthamiana. It is toxic, inducing cell death from transient expression in N. benthamiana, as well as in yeast. Among the four AvrRxo1 alleles from different Xoc strains, we concluded that the toxicity is abolished by a single amino acid substitution at residue 344 in two AvrRxo1 alleles. A series of truncations from the carboxyl terminus (C-terminus) indicate that the complete C-terminus of AvrRxo1 plays an essential role as a suppressor or cytotoxic protein. The C-terminus was also required for the avirulence function, but the last two residues were not necessary. The first 52 amino acids of N-terminus are unessential for toxicity. Point mutagenesis experiments indicate that the ATP/GTP binding site motif A is required for all three functions of AvrRxo1, and NLS is required for both the avirulence and the suppression of non-host resistance. The putative thiol protease site is only required for the cytotoxicity function. These results determine that AvrRxo1 plays a role in the complex interaction with host proteins after delivery into plant cells.
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Provincial Key Laboratory of Agricultural Microbiology, Shandong Agricultural University, Tai an, Shandong, PR China.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Provincial Key Laboratory of Agricultural Microbiology, Shandong Agricultural University, Tai an, Shandong, PR China.
authors.forename: Qingle
authors.initials: Q
authors.lastname: Chang
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Provincial Key Laboratory of Agricultural Microbiology, Shandong Agricultural University, Tai an, Shandong, PR China.
authors.forename: Wenjie
authors.initials: W
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Provincial Key Laboratory of Agricultural Microbiology, Shandong Agricultural University, Tai an, Shandong, PR China.
authors.forename: Baogang
authors.initials: B
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Provincial Key Laboratory of Agricultural Microbiology, Shandong Agricultural University, Tai an, Shandong, PR China.
authors.forename: Tao
authors.initials: T
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Provincial Key Laboratory of Agricultural Microbiology, Shandong Agricultural University, Tai an, Shandong, PR China.
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.affiliation: Biotechnology Research Center, Shandong Academy of Agricultural Science, Jinan, Shandong, PR China.
authors.forename: Fangyin
authors.initials: F
authors.lastname: Yao
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Provincial Key Laboratory of Agricultural Microbiology, Shandong Agricultural University, Tai an, Shandong, PR China.
authors.forename: Xinhua
authors.initials: X
authors.lastname: Ding
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Provincial Key Laboratory of Agricultural Microbiology, Shandong Agricultural University, Tai an, Shandong, PR China.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Chu
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D016415:Sequence Alignment; D014026:Nicotiana / Q000254:growth & development / Q000382:microbiology*; D014974:Xanthomonas / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D015003:Yeasts / Q000254:growth & development / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005656:Fungal Proteins; C489531:avrRxo1 protein, Xanthomonas