Abstract
The His-Asp phosphorelay signal transduction system has been identified in most organisms, including bacteria, yeasts, fungi, and plants, except for animals. This system is important in adaptation to stress, control of cell growth, and induction of development in response to environmental changes. On the basis of genomic information, it has been found that Aspergillus nidulans, a model species of fungi, includes 15 histidine kinases (HKs), one histidine-containing phosphotransmitter protein (HPt), and four reponse regulators (RRs) as factors related to the signal transduction system. In this review, it is explain that the His-Asp phosphorelay system is important in controling cell growth (responses to fungicides, the induction of asexual and sexual development, and so on) under different growth conditions with reference to A. nidulans.