Emerging trends in nitrogen and phosphorus signalling in photosynthetic eukaryotes

Phosphorus (P) and nitrogen (N) are the major nutrients that constrain plant and algal growth in nature. Recent advances in understanding nutrient signalling mechanisms of these organisms have revealed molecular attributes to optimise N and P acquisition. This has illuminated the importance of interplay between N and P regulatory networks, highlighting a need to study synergistic interactions rather than single-nutrient effects. Emerging insights of nutrient signalling in polyphyletic model plants and algae hint that, although core P-starvation signalling components are conserved, distinct mechanisms for P (and N) sensing have arisen. Here, the N and P signalling mechanisms of diverse photosynthetic eukaryotes are examined, drawing parallels and differences between taxa. Future directions to understand their molecular basis, evolution, and ecology are proposed. The expansion of sequencing resources and the development of advanced plant and algal model systems provide a new framework to examine the distribution and evolution of N and P signalling mechanisms in photosynthetic eukaryotes.This has revealed that, although core P-starvation signalling components are conserved, distinct mechanisms for P (and N) sensing may have arisen.Ca2+ signalling is emerging as an important player in N and P sensing in photosynthetic eukaryotes, albeit that distinct roles have evolved in different lineages.Sophisticated mechanisms to integrate N and P signalling networks and maximise nutrient acquisition are employed by diverse photosynthetic eukaryotes.Integration of plant and algal research will expedite advances in our understanding of N and P signalling, and inform strategies to engineer improved N and P use efficiency in crops.