Access MKMapView from another controller

Question

I have a MKMapView on the first of my tab bar items. From my second tab bar item, i want to tap a button "View on map" which loads the first tab ( currently using appDelegate.rootController.selectedIndex=0; in my -buttonClicked method ), and then places a pin annotation view on the map using coordinates i want to pass in...

How can i access my MKMapView from the view controller for my second tab? It is currently only defined in my MapViewController. Does it need to be declared in my app delegate?

Thanks.