Nippon Life Insurance Co. and Putnam Investments of the United States sealed an agreement Tuesday to strengthen their ties in investment trust sales.Under their alliance, the two firms will jointly develop and retail investment trust products and provide asset management services, officials of the two companies said.Investment trusts, similar to mutual funds in the U.S., are expected to play a growing role in managing the nation's personal financial assets, worth 1.2 quadrillion yen.The agreement features a capital tieup plan. By April 1999, Nippon Life will increase the capital of its investment management subsidiary from the current 4 billion yen to 20 billion yen, of which Putnam will provide 10 percent, the officials said.The beefed-up subsidiary will play a key role in the sales of their products in the Japanese market. Putnam will join its executive board and help manage funds collected from Nippon Life customers, the officials said.The investment trust tieup is expected to reinforce another business alliance they have already established in managing corporate pension funds. The two firms are particularly eyeing a new high-risk, high-return pension program modeled after U.S. 401(K) plans, which is likely to be introduced in Japan in the future.Unlike the conventional pension programs with conservative management, funds collected in the new program are also invested in high-risk securities.Nippon Life aims to utilize Putnam's knowhow in global asset management and developing new financial products, while Putnam plans to expand its business here.