As your already using Blueprint using the Aries JPA and JTA features is what you need. For this you need to install those features also (JPA/JTA) and make sure your transaction is of type JTA, with that and using the entity manager of Aries instead of spring you should be on the safe side. A DAO will look more like the following:
<bean id="daoBean" class="dummy.class.name.DaoBean">
<jpa:context property="em" unitname="customer1" />
<tx:transaction method="*" value="Required" />
</bean>
For this to work properly you need to reference the corresponding blueprint schemas.