Syncrepl and selected subtrees

Hi all, I would like a hint on how to syncreplicate only a group of subtrees from a master DIT.

In example, if I have a BaseDN called "ou=root,dc=my_domain" with 4 subtrees at the first nesting level (ou=subtree1, ou=subtree2, and so on..), how can I configure a slave to syncrepl only subtree1 and subtree3?

Graphically: ou=root,dc=my_domain |- ou=subtree1 |- ou=subtree2 |- ou=subtree3 |- ou=subtree4

Of course, I could use a dedicated user with ACL-masqueraded data to her, but what if I couldn't?

Is there a way to express this purpose on the "replica" configuration?

Thanks in advance Marco