Nissan Motor Co. said Thursday it will invest $500 million to transform its assembly plant in Mississippi into a key production base for electric vehicles in the United States, with the aim of manufacturing two new all-electric models including in the luxury Infiniti brand beginning in 2025. The announcement is part of the Japanese automaker’s plan for 40 percent of its U.S. vehicle sales to be fully electric by 2030. Major carmakers are stepping up EV development as the global auto market adapts to demand for environmental responsibility amid growing concerns over climate change. At the Canto…