The Breaking Bad star portrayed Kirsten's onscreen husband in the second season of TV crime drama Fargo, and they began dating in real-life in May (16), following the actress' split from her boyfriend of four years, Garrett Hedlund.

Dunst has spent the past few months preparing for her first big project as a filmmaker, with a new movie adaptation of The Bell Jar, about a young woman's struggle with mental illness.

Dakota Fanning was named as the female lead in July (16), taking on the part of Esther Greenwood, and now Plemons has signed on to co-star, reports Details about his role have yet to be revealed.

The Bell Jar is set in the 1950s and is based on Sylvia Plath's semi-autobiographical 1963 novel of the same name.

It was previously turned into a film by director Larry Peerce in 1979, with Marilyn Hassett as Esther.

Dunst, who has previously taken charge of two short films, 2007's Welcome and 2010's Bastard, is co-writing The Bell Jar script with Nellie Kim, while she will also serve as an executive producer.

Production is expected to begin early next year (17).

Plemons, who also appeared in 2015 films Black Mass and Bridge of Spies, previously expressed his joy at working alongside Kirsten in Fargo, in which they played a husband and wife who cover up their hit-and-run murder of a local mobster.

"It was a gift," he said during a panel interview for Fargo at the 2015 PaleyFest New York. "I loved Kristen's work for a long time, and I was really excited once I'd met her, and she's a great person, and we're both actors that just... have fun with the material."

Kirsten is famously private when it comes to her personal life, and neither she nor Jesse have commented on their new romance.