Dissecting the integration of phosphorus and nitrogen nutrition signals in diatoms

点击翻译按钮获取中文摘要

Phosphorus (P) and nitrogen (N) are the major nutrients constraining growth of plants and algae. Environmental levels of these nutrients can be highly dynamic. It is therefore critical to understand how photosynthetic eukaryotes optimise growth and P and N acquisition, in conditions with fluctuating supply of these nutrients. Alongside surviving prolonged periods of nutrient deprivation, this requires being able to perceive and rapidly adapt to nutrient replenishment. We will employ an important group of aquatic microalgae, the diatoms, as a model system for investigating nutrient sensing, starvation and crosstalk mechanisms. Diatoms exhibit exquisite sensitivity to changes in P and N availability, and often dominate in coastal and estuarine ecosystems where nutrient supply can vary dramatically. We have recently discovered that diatoms employ the universal second messenger, Ca2+, for rapidly sensing and coordinating early cellular responses to P replenishment. However, the molecular players (genes and proteins) underlying P-Ca2+ signalling, and how they coordinate downstream adaptations are unknown. Furthermore, we do not currently know how diatom P sensing mechanisms are coordinated with known P starvation signalling mechanisms to optimise diatom responses to fluctuating P supply. Finally, the importance of bidirectional cross-talk between P and N signalling for mediating balanced acquisition of these vital nutrients remains to be determined. The aim of this proposal is to address the above questions in order to better understand how photosynthetic eukaryotes perceive and respond to changes in the supply of P and N, and optimise growth in dynamic nutrient environments. We will employ established expertise in state-of-the-art gene editing approaches (CRISPR-Cas9) to characterise candidate genes of the P-Ca2+ signalling pathway. Examination of mutants will enable us to assess precisely how diatoms generate and coordinate P-Ca2+ signals to regulate diatom recovery responses from P starvation. We will also characterise whether, and what components of P-Ca2+ signaling are controlled by the master regulator of diatom P starvation responses, PSR1. Finally, we will investigate how N availability influences P-signalling and acquisition, to ensure the balanced acquisition of these vital nutrients. This research will significantly advance understanding of nutrient sensing and crosstalk mechanisms in photosynthetic eukaryotes. As diatoms are evolutionarily distinct from land plants and green algae, the findings will allow us to compare and contrast nutrient signalling mechanisms between diverse photosynthetic taxa. As such, this proposal offers an unprecedented opportunity to gain insight of the evolution of nutrient perception and crosstalk mechanisms in photosynthetic eukaryotes. In doing so, our work will inform research efforts aiming to enhance N and P usage by other photosynthetic eukaryotes, such as important crop species. There is also great interest in using microalgae such as diatoms for removal of P and N from wastewater, to mitigate the harmful impacts of nutrient run-off. This research could therefore inform the optimisation of strains/conditions to maximise P and N recovery. More broadly, the research could also help better manage nutrient run-off and algal blooms, minimising human damage to valuable aquatic ecosystems.