Sulfur

This chapter describes the pathways associated with SO42 - assimilation in Chlamydomonas, the multiplicity of ways in which photosynthesis in eukaryotes can acclimate to limiting S conditions, and the regulatory elements associated with this acclimation process. It also uses Chlamydomonas genomic and experimental information to highlight the similarities and differences of assimilation and acclimation processes between Chlamydomonas and vascular plants. In the case of S deprivation, they are mostly associated with activities that promote scavenging of extracellular S and the recycling of intracellular S. These processes are included with responsive genes. Establishing these links and the specific factors that facilitate this integration would be important for understanding the homeostasis of the cell as it experiences fluctuating environmental conditions. With increased fertilizer purity and decreased occurrence of acid rains, low levels of available S in diverse ecosystems can limit growth and development of plants and microbes. A summary of pathways used in the assimilation of SO42 -, the genes associated with assimilation, and the acclimation of Chlamydomonas to S-limiting conditions, are given in this chapter.