Abstract

Sulfate is a plant macronutrient with strong impact on stress resistance and growth. The various oxidation states of sulfur carry out a large number of essential functions in cells. These include protein structure and regulation, electron transport, redox control and primary and secondary metabolites that operate in catalysis, detoxification or defense. Sulfate uptake, reductive assimilation and channeling into downstream metabolism need to be adjusted according to nutritional status, developmental stage and stress conditions. The responses to demand and supply are coordinated at the cellular and whole plant levels and include transcriptional and metabolic control mechanisms as part of a network of primary metabolic pathways. In particular, the fine-tuning of cellular sulfur status depends on a novel sensing system that is based on reversible dissociation of a multiprotein complex in response to fluctuating metabolite levels. Since cysteine and glutathione synthesis take place in plastids and the cytosol, intracellular communication forms an additional level of control with respect to sulfur and redox homeostasis.

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