Ms eye disc JH nutrition (comment by Leopold Layealle Science 2006)

PERSPECTIVESDEVELOPMENT BIOLOGYEnvironmental cues affect the course of anLinking Nutrition and organism’s development. For example,in some insects, scarce nutrients induce ahormone to block tissue formation.Tissue GrowthPierre Léopold and Sophie Layalleomplex organisms must beMOLT METAMORPHOSISable to adapt their develop-Fourth instar larval stageCmental programs to ever- Fifth instar larval stagechanging environmental condi-MIFJHtions. One important way to coordi-nate this is through the use of hor-mones, regulatory molecules thatTimeexert diverse biological effects onmultiple and remote target tissues.In this context, juvenile hormoneJuvenile hormone (JH) A metamorphosis initiating factorhas fascinated insect endocrinolo-blocks proliferation of (MIF) induced by food stimulates gists for decades. This factor, pres-primordia cells. cell proliferation.ent in insects that undergo meta-Imaginal disc developmentmorphic changes during develop-ment, has many functions in orches-trating the insect life cycle, and thus Coordinating nutrition and hormone influence on tissue development. In the tobacco hornworm M. sexta, imaginalprovides an illuminating example disc tissue forms from primordia tissue late in larval development, after the fifth larval molt. This process is initiated by aof the kinds of pleiotropic effects signal of unknown nature called metamorphosis initiation factor, which is itself triggered by feeding. Shortly afterward,that hormones ...