The MTA is increasing service on a vital bus line that serves the subway-vacant areas of Astoria and Long Island City — home to a growing arts corridor and luxury waterfront communities, officials said.

The Q103, which offers a lifeline to the underserved area, is getting a 20 percent boost in service today, said State Sen. Michael Gianaris.

The morning rush will have the most added service, with a 33 percent increase in the number of buses .

The Q103 had the largest increase in passengers last year of all city buses, at almost 20 percent.

The service boost follows advocacy by Gianaris, who partnered with the Riders Alliance to lobby for better transit options for Astoria and Long Island City.

“As western Queens continues to include our city’s fastest-growing neighborhoods, we need to make sure public transportation keeps up,” Gianaris said.

Bobby Preti, a 27-year-old social worker from Astoria and a member of the Riders Alliance, started pushing for more Q103 buses after finding that it often took less time to walk more than a mile to his internship job than it did to wait for a bus.

“It was definitely frustrating, especially when you see yourself go from early to on time to late,” he said. “You think, ‘If I walked, I would have made it.’ ”

The move is good news for anyone looking to visit the Socrates Sculpture Park, the Noguchi Museum and the art galleries in the area.

The Noguchi Museum, for instance, which features sculptures and a botanical garden, is almost a mile from the N-train’s Broadway stop.