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Figure 5.11
Annular domains of gene expression, plotted along the leg's proximal-distal axis (= peripheral to central in the disc). Genes are grouped based on whether expression is broad, narrow, or iterated, and they are seriated within each group based on proximal limits.
Black bars are regions that express the indicated genes (mRNA or reporter) during late 3rd instar (3), early pupal period (P) or adult (A) stage. Degrees of expression are indicated by shades of gray or by graded slopes. All areas are plotted on an adult template, but not all genes are expressed then. The span of stages (e.g., '3-P') indicates when expression has been seen, but it does not mean that expression is confined to that time. When the claw icon is filled in, this means that two dots (or one solid spot) are detected where claws arise [1587, 2287], though they could be apodemes [33, 3971], and the spot might actually occupy the pretarsus [4401]. See [851, 2287] for histology. See App. 7 for discussion.
Genes whose LOF alleles affect anatomy are in white letters on black background. Wiring at left (—> activation; —| inhibition) shows some genetic interactions (see text or references below at upstream or downstream gene). 'External signal' means that the upstream gene emits a signal (unidentified in both cases depicted) that affects the downstream gene in nearby cells by diffusion (esg —> ? —> dac) or contact (BarH1 —> ? —> FasII). Horizontal T extensions within the template are confidence limits (not inhibitor icons), though their absence does not imply certainty. Charting is more precise in pupal or adult legs than in discs [999]. Sternopleura (Stpl) comes from the leg disc but is not part of the leg per se (Co, coxa; Tro, trochanter; Fem, femur; Tib, tibia; T1-5, tarsal segments; * = pretarsus [2287, 4008]; Cl, claws).
Genes ('DO' = details omitted): al (aristaless; DO: Co expression is dorsal only and Tib expression is ventral only) [618, 881]Δ, ap (apterous) [3474]Δ, bab (bric à brac; note the lower expression in T2) [1516], BarH1 [2287, 3474, 3762], bib (big brain) [999], crol (crooked legs; DO: later spots arise in Tib and Fem) [935], dac (dachshund; DO: dorsal patch outside Tro ring) [4761]Δ, dAP-2 (Drosophila AP-2) [2905], disco (disconnected; DO: squares should actually be bell-shaped) [344]Δ, Dl (Delta) [344, 3525]Δ, dLim1 [3474, 4401], Dll (Distal-less) [4761]Δ, dpn (deadpan) [331], esg (escargot) [1573]; Fas II (Fasciclin II; DO: the ring's perimeter is one-cell wide) [2287]; fj (four jointed; DO: stripes arise asynchronously) [4852]Δ, h (hairy) [3193]Δ, hth (homothorax) [4761]Δ, m8 [a.k.a. E(spl)] [344], nub (nubbin) [3525]Δ, odd (odd skipped; DO: Fem band may be more proximal) [834] (his Fig. 11d), odz (odd Oz; DO: 2nd-leg has more bands in Co and Stpl) [2497], poxn (paired box-neuro) [150], rn (rotund; DO: claws are unstained in some preparations) [881]Δ, Ser (Serrate) [344, 3525]Δ (cf. LOF effects [1944]Δ), trn (tartan) [721], ss (spineless; DO: expression shifts to Stpl in late 3rd instar; cf. tango) [1166]Δ, tsh (teashirt) [4761]Δ. HZ76, HZ84 (DO: spot in dorsal T5), PZ22, and PZ63 are enhancer-trapped transposons [1574]. Dll fills the adult tibia in some stained preparations (not shown) [1561] but only the distal half in others [3242, 4761].
N.B.: Most expression domains are dynamic (e.g., see Fig. 5.12b). In late 3rd instar, the hth ring overlaps the dac ring less than the outer Dll ring [4760]. Depending on proximity to the dac-ON region, Hth either inhibits or activates tsh (not shown) [4761]. Adult defects imply that dac is needed in T2-3 [2689], BarH1 and BarH2 are needed in T3-5 [2287], and al is needed in T4-5 [618]. In pleiohomeoticLOF flies the pretarsus looks transformed into a 6th tarsal segment [1500].
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