Figure 5. Transcriptional Control of Olfactory Receptor Expression and Wiring Specificity in V-ORNs.

(A) tSNE plot showing that fkh is expressed in 2 clusters, one of which corresponds to V-ORNs.

(B) Olfactory receptors Gr63a and Gr21a are co-expressed in V-ORNs. Confocal images of adult antennal lobes showing that ORN knockdown of fkh using peb-GAL4;UAS-dcr2 causes markedly reduced expression of markers driven from transgenes utilizing the promoters of Gr21 and Gr63. Quantified on the right with antennal lobe number (n) on top. Residual marker expression indicates that Gr21a/Gr63a+ axons still target to V.

(C) tSNE plot showing that unpg is expressed in three clusters mapped to V, VA2, and VM5d/VM5v (solid outline). Three unpg-negative clusters are indicated (dashed outline).

(D) Schematic summarizing receptor expression and glomerular targets of all unpg-positive and some unpg-negative ORN types.

(E) Confocal images of adult antennal lobes showing olfactory receptor expression in control (WT) and unpg-RNAi flies. peb-GAL4;UAS-dcr2 was crossed with either w¹¹¹⁸ (WT) or unpg-RNAi, and olfactory receptor promoter-driven reporters were used to monitor receptor expression. In WT flies, Or92a, Or98a, and Gr21a are expressed normally. In unpg-RNAi flies, the expression of all three receptors is lost.

(F) Quantification for the receptor expression in three unpg-positive ORN types and four unpg-negative ones.

(G) In unpg-RNAi flies, Gr21a expression is lost consistently, and Gr63a+ axons show stereotyped mistargeting (arrowheads). Quantifications are shown on the right.

(H) Schematic illustrating the strategy of DiI labeling for four ORN types from the same ab1 sensilla in the antenna: Or42b and Or10a (unpg-negative), as well as Gr21a and Or92a (unpg-positive).

(I) For DiI labeling, Gr63a-syt:GFP is used to monitor V-ORNs. In WT flies, DiI labels VA2 in an anterior section of the antennal lobe, and DM1, DL1 and V in a posterior section. In unpg-RNAi flies, DiI labels a diffuse area (arrowheads) around VA2 in the anterior section, labels DL1 and DM1 normally, and co-labels Gr63a-posistive V-ORNs, which show mistargeting phenotypes. Schematic on the right summarizes DiI labeling in WT and unpg-RNAi flies. Quantifications are shown on the right; antennal lobe numbers (n) are indicated.

(J) Summary of the regulation of olfactory receptor expression and wiring in V-ORNs by transcription factors fkh and unpg.

See also Figure S5.