Genie O’Brien’s announcement that she is leaving Portland Ballet added early drama to “The Victorian Nutcracker” Wednesday night at Merrill Auditorium.

As the house lights went dark and people silenced their phones, O’Brien walked to a lone microphone at center stage. Dancers and colleagues huddled in the wings, sending good wishes to the nervous woman who stood alone on stage.

As far as curtain announcements go, this one started routinely enough. O’Brien thanked supporters of Portland Ballet and lobbied the audience for end-of-year gifts to help the dance company meet its financial goals.

And then she paused.

“So, the big news I’d like to share,” she began tentatively. “As founder and after 35 years as executive and artistic director, this is the last time I will visit you in my current role on this stage at our ‘Victorian Nutcracker.’ ”

The applause came quickly. Some in the audience stood to cheer, showing their appreciation for one of Portland’s longest-serving arts leaders. O’Brien began Portland Ballet in 1980 and guided its development from a niche school focused on classical and contemporary ballet to one of the top dance schools and presenters of modern dance in northern New England.

Its students have danced professionally at companies across the country, including Dance Theater of Harlem, Pacific Northwest Ballet, Nevada Ballet, American Repertory Ballet and Oregon Ballet Theater. The school teaches young dancers the rigors of the profession, while the company gives professional dancers an outlet for their work.

A dance school in a city the size of Portland isn’t unique. But for the city to also have a company of professional dancers, recruited from around the country, who live and work there as artists is unusual, said Creative Portland Executive Director Jennifer Hutchins.

Portland Ballet also presents original work by resident choreographers, something that’s more typical of larger metropolitan dance companies.

The organization’s longevity and success are attributable to O’Brien’s entrenchment in the community. She knows who to call to get things done and isn’t shy about asking them to get involved, Hutchins said.

“Thanks to her dedication and leadership, Portland has its own professional dance company and school that reaches out into the community,” Hutchins said, citing as an example the First Friday Art Walk performances in the windows of the Portland Public Library. “That kind of engagement and professionalism is unique for a city of our size and exemplifies what makes Portland’s arts scene so special.”

O’Brien, 63, will stay on through the spring. In an interview Thursday morning, she said she informed the board of her intentions a year ago.

“It’s time,” O’Brien said. “I do not have any health issues and I am not moving to Florida. It’s just time.”

Melissa Lin, who chairs the Portland Ballet board of directors, said a national search has begun for O’Brien’s replacement on the administrative side. Nell Shipman, Portland Ballet’s associate artistic director and O’Brien’s protégée, will become artistic director. Shipman has risen through the ranks after arriving in Portland in 2004 as a principal dancer. She became resident choreographer in 2007 and O’Brien’s assistant in 2010.

Portland Ballet has an annual budget of $500,000, a professional company of 15 dancers and school enrollment of 130 students. It is poised for growth, Lin said, and recently opened a black box theater – an open, unadorned performance space – adjacent to its studios on Forest Avenue.

The ideal candidate to succeed O’Brien will have experience in both the arts and nonprofit sectors, Lin said, noting that running the theater will be an important responsibility of the new executive director.

As news of O’Brien’s retirement circulated, colleagues praised her vision and dedication.

Running an arts organization requires vigilance and energy, said Portland Ovations Executive Director Aimee Petrin.

“You spend a lot of your days and nights stressed out. You’re always worrying,” Petrin said. “Just realizing she has been doing this for 35 years with what appears to be an unwavering dedication not only to dance, but to the arts in this community, is just astounding. I don’t know how people have it in them to do it for so long and with such integrity. It’s exhausting work.”

Eric Altholz, past board president, got involved with Portland Ballet because his daughter, Eleanor, danced there. She started when she was 5 and worked her way up through the CORPS program, a partnership with local high schools that allows ambitious dancers to earn academic credit. She is now studying dance at Barnard College in New York.

“She shows up for every class knowing what to do, and that’s all because of the training she received at Portland Ballet,” Altholz said. “A lot of her passion was nurtured and her skills honed at Portland Ballet over many, many years.”

Altholz said Portland Ballet was ready for the change. But that doesn’t mean change will be easy.

“You don’t replace someone like Genie. You find a successor,” he said.