Abstract: Cloning systems are provided for constructing expression vectors. In one aspect of the invention, a kit is provided for constructing one or more recombinant expression vectors. The kit comprises: a linear driver DNA comprising a promoter sequence, a donor recombination site, and at least one selectable marker, the linear driver DNA being capable of being ligated with one or more linear donor DNA comprising a donor DNA sequence to form one or more circular donor DNA; and a circular acceptor vector comprising an origin of replication and an acceptor recombination site capable of recombining with the circular donor DNA to form the recombinant expression vector for expressing the donor DNA sequence.

Abstract: Compositions, kits, and methods are provided for use in a recombinational cloning or subcloning methods for constructing expression vectors which comprise: ligating a library of double-stranded linear donor DNAs, where each member of the library includes a donor DNA sequence, with a double-stranded linear driver DNA which includes a promoter sequence and a donor recombination site to form a single circular donor DNA, the single circular donor DNA not including an origin of replication, where the donor DNA sequence is under the transcriptional control of the promoter; and contacting the circular donor DNA and a circular acceptor acceptor vector in the presence of a recombinase to form a single fused circular vector, the circular acceptor vector comprising an origin of replication and an acceptor recombination site capable of recombining with the circular donor DNA.