GAPDH and cyst: Although these were the same places in mature cyst walls where Luke(2)-GFP and Leo-GFP localized under either their own promoters or the GAPDH promoter (Luke(2)-GFP) (Fig 7B, 7C and 7F), these results suggested that glycopolymers bound by MBP-Luke(2) and MBP-Leo in the endocyst layer and ostioles were, for the most part, inaccessible to external probes.