We expressed the Arabidopsis thaliana histone AtHTA1 in rice under the control of the maize ubiquitin promoter. Transformation efficiencies of rice plants that constitutively expressed AtHTA1 were 28-44% higher than calli containing an empty vector control. Furthermore, co-infection of rice calli with a vector containing AtHTA1 and another vector with the target gene increased transformation by 27-50%. Thus, expression of AtHTA1 either transiently or in stably transformed cells improved rice transformation efficiency.