ABSTRACT
In insects, moulting, metamorphosis, and reproduction are events in large part regulated by the hormones, juvenile hormone (JH) and/or ecdysteroids. However, the expression of one hormone is capable of stimulating different responses in different tissues of an organism. In some cases, depending upon the timing and physiological condition, a tissue can respond differently to the same hormonal stimulus. Due to the complexity and sensitivity of developmental and metabolic processes in metazoans, it is of paramount importance that gene expression is precisely timed and located in order for these processes to function correctly. The tight control of developmental gene expression cannot be achieved by the action of these two hormones alone. On the contrary, the presence of JH and/or ecdysteroids at a point in time can only be considered an ubiquitous signal able to activate transcription in a wide variety of tissues where their receptors are present. However, the tissue-, sex-, and stage-restricted expression of hormonal-dependent genes clearly indicates that the correct timing for gene expression must be achieved by a complex cooperation between these hormones and several other transcription factors expressed in a spatially and temporally restricted way.
