Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Types of signalsInducerResponderSetting up a signaling gradient: the role of the wingless geneCells know theirpositions within the body anddifferentiateaccordinglyAnteriorPosteriorA- HairP- Bare Skinsegmentwild typeA = hairP = bare skinTo set up this pattern, flies use the secreted protein Wingless to specify a posterior fatesegmentBePosterior!Cells instruct one anothervia cell-cell signaling pathwaysBePosterior!Cell-cell signaling can be influenced by distance between cellsYes Ma'am!Pardon me?Anterior: Low Wingless,HairsPosterior: High Wingless,Naked CuticleSignals can also actin a graded fashionWingless-expressing cellsWingless diffusesaway from the cellsthat secrete itWingless signaling specifies posterior cell fates in the ventral epidermisarm mutantwild typeALL cells have anterior (hair) fateA = hairP = bare skinTherefore, all cells can see wingless, and the concentration of wingless itself is what determines cell fateSetting up a signal gradientTurn on new genes!Yes Ma'am!Cell surfaceNucleusSignal transduction moves information from the cell surface to the nucleus and other cellular targetsTurn on new genes; pass it onYes Ma'am!Cell surfaceNucleusTurn on new genes; pass it onTurn on new genes; pass it onTurn on new genes; pass it onSignal transduction occurs through a series of stepsGeneticsrevealed theligand andproteins inthis signaltransductionpathwayGenetics can also position proteins within the signaling pathwayAn example of the conservation of key developmentalregulatory machineryacross animal phylaflies mammalsSee also Figure 6.20AColon cancer, the second leading cause of cancer deaths in the U.S.,results from inappropriate Wnt signalingPolyps, the first stageIn tumor developmentInsects:A model systemto study hormonalcontrol ofpostembryonic developmentFigure 18.9Long range signalingVincent B. WigglesworthDiscovered that blood-borne hormones control insect metamorphosis through experiments with a blood-sucking bug, Rhodnius prolixusBlood-bornehormonesregulatethe timing ofmetamorphosisExperiment #1induces 1st instar larva to molt into very small adultExperiment #2Other hormones prevent metamorphosisExperiment #3Other hormones prevent metamorphosisTransplant corpus allatum from 4th to 5th instar larvaResult: blocks metamorphosis, instead get “6th instar larva”AdultThe cascade of hormonesregulating insectmetamophosisFigure 18.16PTTH20ESteroid hormones (ie 20E):hydrophobic signaling moleculesthat can pass through the plasma membrane20EMost signalsSteroid hormones(ie. 20E)An insecticide produced by plants cause premature
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