Will a 2.1 gfx work with a 2.0 mobo?

see im building a computer and all the motherboards i can find support pci express 2.0 and doesnt metion 2.1..... most gfxs are 2.1 pci express.... will a 2.1 pci express gfx work with a motherboard with a 2.0 pci express slot?