Improved GAL4 and Tet OFF drivers for C. elegans bipartite expression

The first generation of C. elegans GAL4 drivers for bipartite expression function less well than C. elegans tet ON/OFF, QF and LexA drivers. The main difference between the GAL4 drivers and the others is the absence of a flexible linker between the DNA binding and activation domain in the GAL4 construct. Addition of a linker to a GAL4-QF construct increased driver potency, while adding linkers to a GAL4-VP64 driver was much less effective. Extending the linker region of the tetR-L-QF driver also increased activity of that driver. The new GAL4 driver makes GAL4/UAS bipartite system activity comparable to the other worm bipartite expression systems.