UPDATE 1-BMW and China partner in $735 mln mainland expansion

* Construction on second plant planned to begin in 2010

* Second plant will have annual capacity of 100,000 units

* Existing plant capacity to rise to 75,000 units from 30,000

(updates with details, background)

BEIJING, Nov 12 (Reuters) - BMW (BMWG.DE) and its partner, the state parent of Brilliance China Automotive (1114.HK), will invest $735 million to expand their capacity in the world's largest vehicle market.

The total long-term investment of BMW and joint venture partner Brilliance Auto Group is expected to eventually exceed 5 billion yuan, BMW said in a statement.

"Today, China is a global driver of growth in the automotive market," Friedrich Eichiner, a board member of the BMW Group, told reporters.

"China will play a major role in the global automotive business, in the development of future technologies," he said.

The new investment includes expansion of an existing plant in in the northeastern Chinese city of Shenyang, where Brilliance, the country's eighth-largest automaker, and BMW now manufacture BMW 3-series and 5-series sedans.