Construction of a 51-story office and residential tower at Boston’s South Station could begin next spring following approval of updated plans by the Boston Planning and Development Agency.

Houston-based real estate firm Hines added Chinese developer Gemdale Properties & Investment Corp. as a partner this year to jumpstart the project. The BPDA on Thursday approved changes to the plans originally approved in 2006 at the Massachusetts Department of Transportation-owned site, which was recently renamed the Michael S. Dukakis Transportation Center. Beginning 9 stories above ground, the Pelli Clarke Pelli-designed tower will include 26 stories of office space topped with 16 floors of condominiums.

Before they break ground, the developers need MBTA approval for the bus terminal upgrades and a construction management plan, according to a spokeswoman.

Hines and Gemdale estimate the project will create 5,300 permanent jobs and pay $26 million in annual property taxes. Expansion of the station’s bus terminal will increase its capacity by 50 percent.

At 677 feet, the tower would become the fourth tallest building in Massachusetts after the former Hancock Tower at 200 Clarendon St., the original Prudential Center tower and the Millennium Tower Boston.