Animals must detect water in their environment to stay alive, but the molecular basis for water detection has been unclear. Here the essential mediators of water-sensing and drinking in fruitflies have been identified: an ion channel of the degenerin/epithelial sodium channel family, and the sensory neurons that make it

Before mating, a yeast cell must detect a partner cell that is close enough and expresses sufficiently large amounts of a sex pheromone. The mating decision is an all-or-none, switch-like response to pheromone concentration. It is now shown that this decision involves the competition of one kinase and one phosphatase enzyme for multiple phosphorylation sites on a 'scaffold' protein. The results should prompt a re-evaluation of the role of related signalling molecules that have been implicated in cancer

The ability of plants to 'green' in the dark is attributed to the activity of the dark-operative protochlorophyllide oxidoreductase (DPOR). This enzyme catalyses the stereospecific reduction of the C17=C18 double bond of protochlorophyllide to form chlorophyllide a, the direct precursor of chlorophyll a. The X-ray crystal structure of the catalytic component of DPOR has now been solved. A chemical mechanism is proposed by which the reduction of the double bond may occur