2. HeadTail T1 T2 T3 A1 A2A4 A5 A6 A7 A3 A8 Metamorphosis Quiltwork Assembly of a Fly

3. Outline of Vein Development M L1 L2 L3 L4 L5 3rd Larval Instar Early Pupa M L1 L2 L3 L4 L5 L6 sCo Mid-Pupa->Adult

4. L1 L2 L3 L4 L5 M Fly Wing

5. L2 L3 L4 L5 sal Determining the Positions of Veins hh L2 dpp A P En En -> Hh -> Diffuses -> dpp in A/P Organizer Dpp Dpp -> Diffuses -> sal -> L2 vein A P L5 sal L3 L4 L3 L4 Organizer A/P dpp L2 L3 L4 L5

6. hh- mutant L2 L3 L4 L5 WT L2 L3 L4 L5 hh dpp Mutant with reduced hh function A P En L3 L4 dpp Hh Determines Positions of L3 and L4 Veins hh dpp A P En L3 L4 En -> Hh -> Diffuses -> dpp in A/P Organizer

7. dpp- mutant L2 L3 L4 L5 L2 Dpp A P L5 sal L3 L4 sal Mutant with reduced dpp function WT L2 L3 L4 L5 L2 Dpp A P L5 sal L3 L4 Dpp -> Diffuses -> sal -> L2 vein Dpp Determines Positions of L2 and L5 veins

8. Veins Form At Boundaries Along the A/P Axis L2 L3 L4 sal salDpp AP Dpp -> Diffuses -> sal -> L2 vein L5 + En hh dpp + dpp AP Organizer A/P En -> Hh -> Diffuses -> dpp in A/P Organizer

9. sal sal Dpp AP Dpp defines anterior border ofsal domain + En hh dpp + dpp AP En-5 defines position of dpp stripe in wing disc Hb eve-3 Hb defines anterior border ofeve-3 stripe Kni Wing Disc en-5 Eve-3 defines anterior border ofen-5 stripe MaternalBicoid gradient defines posterior limit ofhb Ant.Post. Lowest level of Bcd needed to activate hb Sal defines position ofL2 vein stripe salDpp + + Sal L2 X L2 AP The Developmental Path From Bcd to the L2 Vein

10. Drosophila Melanogaster L1 L2 L3 L4 L5 M CraneflyPsychodid Mosquito Lacewing Syrphid

11. D ->V Signal V -> D Signal ap Expressing Cells ap Non-expressing Cells D V Activation of Notch Along Future Margin Ap -> Notch -> Wing Margin = D/V Organizer D/V Signaling Is Required for Wing Margin Formation and Wing Outgrowth D/V Organizer -> Margin Formation and Wing Growth ap- cells Wing imaginal disc in larvaAdult wing (viewed end on) Adult wing withap- patch Loss ofap in Dorsal Cells -> Margin Formation Intersection of the D/V and A/P Organizers Induces Leg Outgrowth D/V Organizer A P A/P Organizer Distalless Expression Distalless Distal Proximal Normal Legdistalless Mutant Leg D V Fig. 4.4

12. Fly Eye

13. A P Specification of the eye disc in the embryo >1,000-X growth eyeless: A master eye gene? Eye Primordium 20-40 Cells Furrow AP Growth and patterning of eye imaginal disc in larvae dpp hh Early Steps in Fly Eye Development

14. Sequential formation of photoreceptor clusters R8 R7 Furrow R2 R5 R3 R4 R8 R1 R6 R7 87351 Photoreceptor Development R8 R7 Sevenless Receptor Boss Ligand Boss-> Sevenless Signaling Specifies R7 Late Steps in Fly Eye Development