摘要:

The development of the olfactory sense organs on the antenna of the fruit flyDrosophilautilises mechanisms distinct from those used in the rest of the adult peripheral nervous system,lozenge(lz) is the only locus hitherto identified as required for the development of antennal sense organs. In addition to effects on the antenna, mutations inlzalso affect the development of the eye and maxillary palp. We have used the readily- scored eye-phenotype in a temperature sensitivelzallele to screen for dominant modifiers of phenotypes at this locus. We analyse the phenotypes of both intragenic and extragenic modifiers. Our results reinforce the view from developmental studies thatlz+functions in eye and antennal development in distinct ways.

ISSN:0167-7063    

DOI:10.3109/01677069509083460

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The mutationno action potentialtemperature itive(napts) induces arrhythmia in the heartbeat ofDrosophila melanogasterlarvae at temperatures above 20°C; heartbeat becomes normally rhythmic again after a shift back to 20°C. For this phenotype,naptsis almost completely recessive to the wild type.naptsalso reduces the temperature-sensitivity of heart rate over a wide range of temperatures, for this phenotype,napts, is dominant over the wild type,naptscauses reversible paralysis in adults by epistatic effects on the expression ofparalytic, a gene encoding a voltage-dependent sodium channel. However, theparamutation, which induces paralysis in adults at 29°C, has no effect on larval heartbeat at temperatures between 20°and 37.5°C. Theperiodgene,contraearlier reports, has no effect on heartbeat.

ISSN:0167-7063    

DOI:10.3109/01677069509083461

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The temperature-sensitive mutations of theshibire(shi) gene inDrosophilacause endocytic arrest, resulting in neurotransmission block and paralysis at high temperatures. However, underlying mechanism for the defects is not yet known. We examined the subcellular distribution of dynamin, a product of theshigene, by immunoblotting and immunocytochemical assays. Two isoforms of dynamin with apparent Mrof 92 kD and 94 kD have been detected in wild-type andshitsadult neural tissue. The two isoforms were reproducibly associated with different subcellular fractions of head homogenates. The 94kD isoform is fractionated in the low speed (2,000×g) pellet containing plasma membrane fragments, and the 92kD isoform in the high speed (130,000×g) pellet. In this procedure, very little dynamin remained in the high speed supernatant fraction. The 94 kD isoform represents the majority (65–75%) of total dynamin and appears to be a peripheral membrane protein. It can be extracted from the low speed membrane pellet by high salt, Na2CO3(pH 11) or Triton X-100 treatments. Extracted 94kD dynamin from both wild-type and mutant homogenates is able to reassociate with artificial phospholipid vesicles at both permissive and restrictive temperatures. Binding of the 94 kD dynamin to liposomes appears to be pH-dependent, varying most significantly within the physiological pH range, which may be functionally important. The 92 kD isoform cannot be released by high salt or Na2CO3treatments and only a small fraction is released by Triton X-100, suggesting a different mechanism of association with cell structures. The distribution of the two isoforms is not altered by the presence of stabilized microtubules in homogenates. No apparent degradation or subcellular redistribution of mutant dynamin was detected in twoshitsalleles after heat shock or block of the dynamin GTPase activity, suggesting that intracellular redistribution or degradation of mutant dynamin are not involved in the endocytosis arrest in these mutants. These observations resemble the effect of endocytosis'arrest by GTP-gM-S in rat brain synaptosomes (Takeiet al., 1995), in which dynamin is trapped at the neck of invaginated pits but is absent in the clathrin-coated distal end undergoing internalization. Our finding that endocytosis arrest byshitsmutations and GTP-gM-S do not lead to cumulation of dynamin in the low speed pellet fraction further suggests that the 94 kD isoform remains associated with the plasma membrane during coated vesicle pinch-off and that the two isoforms do not appear to correspond to different functional states of dynamin but are likely to be involved in separate cellular compartments within the membrane cycling pathway (e.g., the plasma membrane, endosomes, and endoplasmic reticulum).

ISSN:0167-7063    

DOI:10.3109/01677069509083462

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor