Listing sub domain posts on main domain home page like about.com

I want to display subdomain's posts on main domain home page in Wordpress (not multi site).

e.g. domain is domain.com and subdomaisn are subdomain1.domain.com; subdomain2.domain.com; subdomain3.domain.com same as http://about.com

I've been trying to figure this out but to my surprise I can't find an answer.

I do really appreciate any help. Thank you very much in advance!

via Chebli Mohamed