RT-PCR control for Vitis vinifera - (Aug/01/2006 )

hello,
I am begginig RT-PCR amplification of Vitis vinifera leaves, but I would like to test my RNA isolation with a positive control. Is there any protein, abundant in grape vine leaves, that is commonly used as a control for cheking RNA/DNA isolation?

Thank you

I think the most relevent positive control would be the leaves Vitis vinifera itself.
what methods you used to isolate DNA/RNA?

I may not be understanding the problem correctly, but can you not just check for your housekeeping gene?