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 and 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 and is toxic, inducing cell death from transient expression in N.benthamiana, as well as in yeast.Among the five AvrRxo1 alleles from different Xoc strains, we concluded that the toxin function is abolished by a single amino acid substitution at residue 344 of two AvrRxo1.A series of truncations from the carboxyl terminus (Cterminus) indicated that the complete C-terminus of AvrRxo1 plays important functional roles as a suppressor or cytotoxic protein.The C-terminus was also required for avirulence function, but the last two residues were not necessary.The amino terminus (N-terminus) was unessential for toxicity.And the Nterminus was also observed to compete with the nuclear localisation sequence (NLS) motif to anchor the AvrRxo1 to the plasma membrane.Point mutation experiments indicated that the ATP/GTP binding site motif A is required for all three functions of AvrRxo1, and NLS is required for avirulence and suppression of nonhost resistance.The putative thiol protease site is only required for cytotoxin function.