Red/far-red light signals regulate the activity of the carbon-concentrating mechanism in cyanobacteria.

Abstract

Desiccation-tolerant cyanobacteria can survive frequent hydration/dehydration cycles likely affecting inorganic carbon (Ci) levels. It was recently shown that red/far-red light serves as signal-preparing cells toward dehydration. Here, the effects of desiccation on Ci assimilation by <i>Leptolyngbya ohadii</i> isolated from Israel's Negev desert were investigated. Metabolomic investigations indicated a decline in ribulose-1,5-bisphosphate carboxylase/oxygenase carboxylation activity, and this was accelerated by far-red light. Far-red light negatively affected the Ci affinity of <i>L. ohadii</i> during desiccation and in liquid cultures. Similar effects were evident in the non-desiccation-tolerant cyanobacterium <i>Synechocystis</i> The <i>Synechocystis</i> Δ<i>cph1</i> mutant lacking the major phytochrome exhibited reduced photosynthetic Ci affinity when exposed to far-red light, whereas the mutant Δ<i>sbtB</i> lacking a Ci uptake inhibitory protein lost the far-red light inhibition. Collectively, these results suggest that red/far-red light perception likely via phytochromes regulates Ci uptake by cyanobacteria and that this mechanism contributes to desiccation tolerance in strains such as <i>L. ohadii</i>.