Journal Article

Sulfate Metabolism in C₄ Flaveria Species Is Controlled by the Root and Connected to Serine Biosynthesis

Walker, Berkley J., Krueger, Stephan, Kopriva, Stanislav, Gerlich, Silke C.

2018

Overview

The evolution of C₄ photosynthesis led to an increase in carbon assimilation rates and plant growth compared to C₃ photosynthetic plants. This enhanced plant growth, in turn, affects the requirement for soil-derived mineral nutrients. However, mineral plant nutrition has scarcely been considered in connection with C₄ photosynthesis. Sulfur is crucial for plant growth and development, and preliminary studies in the genus Flaveria suggested metabolic differences in sulfate assimilation along the C₄ evolutionary trajectory. Here, we show that in controlled conditions, foliar accumulation of the reduced sulfur compounds Cys and glutathione (GSH) increased with progressing establishment of the C₄ photosynthetic cycle in different Flaveria species. An enhanced demand for reduced sulfur in C₄ Flaveria species is reflected in high rates of [³⁵S]sulfate incorporation into GSH upon sulfate deprivation and increased GSH turnover as a reaction to the inhibition of GSH synthesis. Expression analyses indicate that the 𝛾-glutamyl cycle is crucial for the recycling of GSH in C₄ species. Sulfate reduction and GSH synthesis seems to be preferentially localized in the roots of C4 species, which might be linked to its colocalization with the phosphorylated pathway of Ser biosynthesis. Interspecies grafting experiments of F. robusta (C₃) and F. bidentis (C₄) revealed that the root system primarily controls sulfate acquisition, GSH synthesis, and sulfate and metabolite allocation in C₃ and C₄ plants. This study thus shows that evolution of C₄ photosynthesis resulted in a wide range of adaptations of sulfur metabolism and points out the need for broader studies on importance of mineral nutrition for C₄ plants.

• Publisher: American Society of Plant Biologists
• Subject: BIOCHEMISTRY AND METABOLISM