Adulthood-specific expression of tkv^GD2549 under the combined control of Scer\GAL4^esg.PU and Scer\GAL80^Su(H).GBE (together with Gal80[ts] for the temporal regulation of expression) prevents re-establishment of quiescence (phospho-H3)in the adult gut upon Ecc15 bacterial infection, leading to dysplasia 2 days after infection; upon Pseudomonas entomophila infection, there is an increase in gut barrier dysfunction (in Smurf assays) and increased mortality, as compared to controls.

Adulthood-only expression of tkv^GD2549 under the combined control of Scer\GAL4^esg.PU and Gal80[ts] (induced by temperature shift from 18[o]C to 29[o]C) leads to the adult posterior midgut showing increased numbers of intestinal stem cells and enteroblasts (i.e. esg-, Dl- and GBE+Su(H)-positive cells), but no changes in the numbers of enteroendocrine cells, and showing increased mitotic index (pH3-positive cells), as compared to controls; the size of the polyploid cells expressing tkv^GD2549 is smaller than fully differentiated enterocytes, indicating a defect in maturation.

In wild-type flies, the pH of the anterior and posterior midgut are over 4.6, while in the copper cell region the pH is less than 3.0. In flies expressing tkv^GD2549 under the control of both Scer\GAL80^ts.αTub84B and Scer\GAL4^esg-NP5130, the pH is uniformly above 4.6 throughout the midgut, demonstrating that functional copper cells are not made.

Expression of tkv^GD2549 under the control of Scer\GAL4^GMR24H06 for 8 days leads to a dramatic increase in mitotic cell numbers in the posterior midgut as compared with sibling co

Expression of tkv^GD2549 under the control of Scer\GAL4^{Myo31DF-NP0001} has no effect on mitotic cell numbers in the posterior midgut as compared to sibling controls.

rols.

Adults expressing tkv^GD2549 under the control of Scer\GAL4^elav.PLu (in the presence of Dcr-2^Scer\UAS.cDa to increase the efficiency of RNAi) do not show a significant defect in avoidance of noxious temperature (46[o]C) compared to control flies.

Expression under the control of Scer\GAL4^pnr-MD237 results in the absence of 100% of the Scer\GAL4^pnr-MD237-expressing area of the notum.