Taking all these findings into account , we suggest that at least six genes , VMA 1 ( CLS 8 , subunit a ) , VMA 2 ( subunit b ) , VMA 3 ( CLS 7 , subunit c ) , VMA 11 ( CLS 9 ) , VMA 12 ( CLS 10 ) , and VMA 13 ( CLS 11 ) , are required for expression of the vacuolar membrane H ( + ) ATPase activity . . ^^^