Reg:act_as_tree

HI

am using acts_as_tree and yui to generate tree structure,
as per the DB is consern for acts_as_tree,the parent and child nodes
are from one table…

i have two different table like

region table

pk name
1 hyderabad
2 chennai
3 bangalore

area tabel
id name fk
1 madhapur 1
2 hi-tech 1
3 kondapur 1
4 adayar 2
5 ECR road 2
6 anna nagar 2
7 whitefiled 3
8 MGM 3

so i need name in region table as root node and the respective fk
names in area table as child nodes(i dont need subchild node )…

how can i use acts_as_tree for this table,are is there an alternative
to do this