A heretofore unknown molecular mechanism helps plants save water in extreme drought and intense sunlight. A research team at Heidelberg University's Center for Organismal Studies (COS), in cooperation with partners at Nanjing Agricultural University (China), has discovered that a protein complex—the cysteine synthase complex—serves as a sensor in the chloroplasts. It receives and forwards stress signals and ensures that the hormone abscisic acid is formed via biosynthesis. This hormone triggers the closure of tiny pores on the leaves, thus preventing water loss.