A novel 'two-component' protein containing histidine kinase and response regulator domains required for sporulation in Aspergillus nidulans

We have characterised a novel Aspergillus nidulans gene encoding a 'two-com ponent' signalling protein (tcsA). tcsA encodes both a histidine kinase dom ain and a response regulator domain similar to those found in bacterial, lo wer eukaryotic and plant members of the two-component family of proteins, w hile two PAS domains in the amino-terminal region of the predicted tcsA pro duct may monitor the signal which regulates a tcsA histidine kinase-respons e regulator phosphorelay. While tcsA is nonessential for vegetative growth, cells lacking the gene are unable to produce conidia on standard Aspergill us growth media. However, tcsA is not absolutely required for production si nce this defect is suppressed by growth on 1 M sorbitol.