Boston Mayor Michelle Wu said she plans to appoint a member to the city’s new seat on the MBTA Board of Directors before its next meeting in September.

The mayor represented the city for the first time at a Thursday board meeting, after being granted the authority to appoint a new Boston-specific representative through this year’s state budget.

“You all have no idea how excited I am to be here,” Wu, a self-described T rider, told the board. “This is just such a gratifying and fulfilling moment, I believe, for the entire city of Boston.”

Wu and other city officials had long advocated for the seat as a way to have a direct role in the governance of their public transportation system. There was momentum for the change last year, but the Boston seat was scrapped during last-minute budget negotiations.

This year’s state budget expands the MBTA Board of Directors from seven to nine members. As mayor, Wu appoints a member to the Boston seat. The governor’s office is conducting a search for the other new seat, from the 175 surrounding municipalities served by the agency, T board Chair Thomas Glynn said.

Glynn described the board’s expansion, evident for the first time through Wu’s participation on Thursday, as a “historic occasion.”

Wu said she was keeping the seat warm while the city conducts a search process for its new representative. She plans to have someone in place by the board’s Sept. 28 meeting.

In a civic engagement process launched last week, the mayor said she was seeking candidates who are residents of Boston, public transit riders, connected to communities of transit riders, and committed to high-quality, reliable and affordable public transportation.

Residents have until Sept. 5 to submit ideas to help inform the city’s search, or indicate their interest in the position.