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First published online 17 March 2004
doi: 10.1242/dev.01068

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Hormonal signals produced by DAF-9/cytochrome P450 regulate C. elegans dauer diapause in response to environmental cues

Max-Planck-Institut für Molekulare Genetik, Ihnestrasse 73, D-14195 Berlin, Germany

View larger version (38K): [in a new window]   Fig. 1. Mosaic analysis. (A) daf-9(dh6) dhEx66 [daf-9::gfp, lin-15(+)] expression mosaics. Loss (–) or retention (+) of expression from hypodermis (H) or XXX cells (X), and effects on mode of growth (Daf-c, Reproductive) and broods. (B) Fate map of the early blastomeres. XXXL/R arise from AB, hypodermis from AB and C (bold). Genotypic mosaics of dhEx107 [daf-9::gfp, sur-5::gfp, ncl-1(+)] in daf-9(dh6) ncl-1(e1865) (C), and dhEx24 [T13C5, sur-5::gfp] in daf-9(dh6) (D). daf-9(+) or (–) genotypes of the blastomeres are indicated beneath, with phenotypic mode of growth.

View larger version (92K): [in a new window]   Fig. 2. Constitutive hypodermal overexpression rescues daf-9 larval phenotypes. (A) N2 wild type, gonadal distal tip cells (arrowhead) turn normally, as diagrammed in B. (C) daf-9(rh50), distal tip cells fail to turn and remain on the ventral body wall (Mig), shown in B. (D) dhEx217 [pdpy-7::daf-9] transgene rescues rh50 Mig phenotypes. (E) daf-9(dh6) Daf-c dauer larva. (F) dhEx217 transgene rescues dh6 Daf-c phenotypes. v, vulva. (G) daf-9::gfp fusion constructs. Expression in hypodermis (H), XXX cells (X) and spermatheca (S), and rescue activity in daf-9(dh6) or daf-9(e1406).

View larger version (55K): [in a new window]   Fig. 3. Thermal influences on N2 dhIs64 expression. (A) DIC micrograph of head region of an L3 larva. (B-G) gfp fluorescent images. All panels are reproductive L3 larvae, except E and G, which show a dauer larva. Hypodermis (arrowheads) and XXX cells (X). Growth temperature and expression level (–, +, ++, +++) are indicated. C-E) are taken at 200 ms exposure time, (B) at 800 ms. (H-K) Quantitation of daf-9::gfp(dhIs64) intensity measurements. (H) Hypodermis of L3 and L3d (dauer) as well as (I) XXX cells. (J) XXX cells and (K) spermathecae of 2-day-old adults.

View larger version (52K): [in a new window]   Fig. 4. Influence of cholesterol, food, and pheromone on daf-9 expression of L3. (A) N2 dhIs64 grown on normal nematode growth (NG) media. (B) N2 dhIs64 grown on NG lacking added cholesterol (NG – chol). (C) N2 dhIs64 dauer larva grown on NG agarose lacking cholesterol (– chol). (D) daf-12(rh61rh411) dhIs64 grown on NG lacking cholesterol. (E) Hypodermal daf-9 expression with increasing dilutions of 2% DH5. (F) Hypodermal daf-9 expression at different concentrations of pheromone. Hypodermis (arrowheads) and XXXL/R cells (X). daf-9::gfp intensity (–, +, ++, +++), see Fig. 3. Worms are cultured at 20°C.

View larger version (62K): [in a new window]   Fig. 5. Hypodermal daf-9 expression depends on daf-9 and daf-12. (A) N2 dhEx94, hypodermal daf-9 is weakly expressed. (B) daf-9(rh50) dhEx94, hypodermal daf-9 is overexpressed. (C) daf-9(dh6) dhEx94, Daf-c dauer larva, hypodermal daf-9 is not expressed. (D) daf-12(rh61rh411) dhIs64 at 25°C, daf-9 is expressed in XXX (X) but not hypodermis (compare with N2 in Fig. 3). (E) daf-12(rh273) dhIs64, hypodermal daf-9 is overexpressed in reproductively growing larva but (F) not expressed in Daf-c dauer larva. Worms are L3s and grown at 20°C, except where indicated.

View larger version (87K): [in a new window]   Fig. 6. Hypodermal daf-9 regulation by genetic inputs. All panels are L3 reproductively growing larvae, except C, a dauer larva. XXX cells (X), hypodermis (arrowheads).

View larger version (43K): [in a new window]   Fig. 7. Feedback model for diapause regulation (see Discussion). XXX cells (X) and hypodermis (H).