UPDATE 1-Tesla, Toyota teaming up in California-governor

* Tesla, Toyota partnering to build electric cars

* Tesla says to make “significant”announcement in briefing

(Adds background on Toyota’s NUMMI plant and Tesla)

FREMONT, Calif., May 20 (Reuters) - Japanese carmaker Toyota Motor Corp 7203.T and electric carmaker Tesla Motors plan to partner on electric vehicles in California, the state's governor said on Thursday.

Governor Arnold Schwarzenegger, speaking at an unrelated event at search giant Google Inc's GOOG.O headquarters, said Tesla will electrify one of Toyota's cars in California, a spokeswoman for the governor confirmed him as saying.

Silicon Valley-based Tesla is holding a press conference later on Thursday where it said it plans to make a “significant and exciting” announcement. The governor will be at the briefing, to be held at the company’s Palo Alto, California, facility.

A Tesla spokeswoman did not immediately return a call seeking comment. A Toyota spokesman could not be immediately reached.

Schwarzenegger let the news slip while announcing the formation of a green-products innovation institute.

Tesla, the six-year-old start-up best known for its $109,000 all-electric Roadster, has been granted $465 million of loans from the U.S. government to build a new lower-cost model. It has been hunting for a manufacturing site in California.

Toyota, on the other hand, closed a sprawling manufacturing plant in Fremont, California, in April, laying off over 4,500 workers.

A deal with Tesla may help repair Toyota’s image in the San Francisco Bay Area, which has often been witness to auto workers rallying against the automaker’s decision to close the plant.

Tesla had been under pressure to consider the now-defunct New United Motor Manufacturing Inc (NUMMI) plant for building electric cars, but it has said the site was too large for the company.

Toyota, meanwhile, is developing a plug-in electric version of its popular Prius hybrid car and hopes to have the car available to consumers in two to three years.

Reporting by Poornima Gupta; Editing by Steve Orlofsky, Bernard Orr; 415 348 4720