Fig. 1.

Mkk3-p38 signaling in ECs promotes ISC proliferation upon damage. a, b Both p38a and p38b (p38a + b) are activated in ECs upon P.e. infection. p38 activation increased in ECs of P.e.-infected control (EC-specific, Myo1A^ts) midguts (b right, red) compared with uninfected control midguts (a right, red). c p38 is activated in the midguts upon pathogen infection. Mean (with s.e.m.) phospho-p38 levels are increased in P.e.-infected midguts (n = 3 midguts from one experiment) compared with uninfected control midguts (n = 3 midguts from one experiment) (unpaired t test (on data not normalized to control); P = 0.0085). d Both p38a and p38b are required in ECs to promote ISC proliferation upon P.e. infection. The ISC response is blocked in P.e.-infected midguts expressing p38a + b^RNAi in ECs for 5 days with Myo1A^ts compared with P.e.-infected control (Myo1A^ts) midguts (Mann–Whitney; P < 0.0001). The mean number of phosphorylated histone H3 Ser 10-positive cells per midgut with s.e.m. in control midguts (n = 55 midguts), P.e.-infected control midguts (n = 53 midguts), midguts expressing p38a + b^RNAi in ECs for 5 days (n = 28 midguts) and P.e.-infected midguts expressing p38a + b^RNAi in ECs for 5 days (n = 32 midguts). Midguts pooled from three independent experiments. e, f Mkk3/Licorne can activate p38 in ECs. p38 activation increased in the midguts overexpressing Licorne in ECs for 2 days with Myo1A^ts (f, red) compared with control midguts (e red). g Overexpression of Mkk3/Licorne in ECs for 2 days with Myo1A^ts promotes ISC proliferation. The mean number of phosphorylated histone H3 Ser 10-positive cells per midgut with s.e.m. in control (Myo1A^ts) midguts (n = 31 midguts) and in midguts expressing lic in ECs for 2 days with Myo1A^ts (n = 24 midguts) (Mann–Whitney; p < 0.0001). Midguts pooled from three independent experiments. h–j Mkk3/Licorne is required for p38 activation in ECs upon P.e. infection. p38 activation increases in ECs in P.e.-infected control (Myo1A^ts) midguts (i right, red) compared with uninfected control midguts (h right, red). p38 activation is blocked however in P.e.-infected midguts expressing lic^RNAi for 7 days with Myo1A^ts (j right, red) compared with P.e.-infected control midguts. DNA is in blue. Scale bars in a, b, e, f, h–j are 50 μm. Representative images in a, b, e, f from three experiments; h–j, two experiments. Source data are provided as a Source Data File