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. 2006 Sep;174(1):253-63.
doi: 10.1534/genetics.106.061978. Epub 2006 Jul 2.

Melanotic mutants in Drosophila: pathways and phenotypes

Affiliations

Melanotic mutants in Drosophila: pathways and phenotypes

Svetlana Minakhina et al. Genetics. 2006 Sep.

Abstract

Mutations in >30 genes that regulate different pathways and developmental processes are reported to cause a melanotic phenotype in larvae. The observed melanotic masses were generally linked to the hemocyte-mediated immune response. To investigate whether all black masses are associated with the cellular immune response, we characterized melanotic masses from mutants in 14 genes. We found that the melanotic masses can be subdivided into melanotic nodules engaging the hemocyte-mediated encapsulation and into melanizations that are not encapsulated by hemocytes. With rare exception, the encapsulation is carried out by lamellocytes. Encapsulated nodules are found in the hemocoel or in association with the lymph gland, while melanizations are located in the gut, salivary gland, and tracheae. In cactus mutants we found an additional kind of melanized mass containing various tissues. The development of these tissue agglomerates is dependent on the function of the dorsal gene. Our results show that the phenotype of each mutant not only reflects its connection to a particular genetic pathway but also points to the tissue-specific role of the individual gene.

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Figures

F<sc>igure</sc> 1.—
Figure 1.—
Melanizations and melanotic nodules. Melanotic nodules isolated from the hemocoel of dronc2/dronc51 (A and B), cact A2 (C and D), and spagk12101(E and F). Trachea isolated from Pr-Set720 (G and H; note melanization within the circles), Su(var)20502/Su(var)20504 (I and J; darkening tissue and melanized spot within the circles), nodules in the intestine observed in dronc2/dronc51 (K and L), mxc22a-6 (M and N), Arkk11502 (O and P), and dcp-1k05606 (Q and R). Melanization of salivary gland cells in Arkk11502 (S and T). In B, D, F, H, J, L, N, P, R, and T, tissues were stained with anti-Hemese (red), phalloidin for F-actin (green), and Hoechst33258 for DNA (blue). Bar, 40 μm.
F<sc>igure</sc> 2.—
Figure 2.—
Melanotic nodules. Confocal crossections taken close to the surface of melanized nodules derived from (A) HopTum/+, (B) l(3)mbnE1/+, (C) Su(var)20502/Su(var)20504, (D) zfrp8M-1-1, (E) Toll10B/+, and (F, I, and J) cact A2. Muscle and tube-like structures are indicated with arrows and polyploid nuclei with arrowheads in I and J. (G and H) cact A2 and dl2. Tissues were stained with anti-Hemese (red), phalloidin for F-actin (green), and Hoechst33258 for DNA (blue). In A–H, Hemese staining alone is shown in the top panels. The melanized foci usually do not stain and are indicated by stars. Bar, 40 μm.
F<sc>igure</sc> 3.—
Figure 3.—
Participation of lamellocytes in melanotic nodule encapsulation. Confocal crossection through the central part of melanotic nodules derived from (A) l(3)mbnE1/+, (B) spagk12101, (C) hopTum/+, (D) Toll3/+, (E) Su(var)20502/Df(2L)TE29Aa-11, (F and G) zfrp8M-1-1/Df(2R)SM183, and (H, I, and J) cact1 and cactG8. Tissues were stained with L1-lamellocyte-specific antibodies (red), phalloidin for F-actin (green), and Hoechst33258 for DNA (blue). L1 staining alone is shown in the top panels; melanized tissues (indicated with stars) generally do not stain (A, B, E, G, and I), but sometimes accumulate the L1 marker (D and F) . Bar, 40 μm.

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