Scientists describe a new role for calcium ion signalling in eukaryotes, for phosphate sensing, for the first time.

MBA researchers Katherine Helliwell, Glen Wheeler and Colin Brownlee in collaboration with scientists at Plymouth Marine Laboratory (PML) and the University of Warwick have shed light on how diatoms (a type of eukaryotic algae) sense the availability of phosphorus, a vital macronutrient which controls diatom growth and productivity in the oceans. The research, which has been published in the journal Current Biology [1], demonstrated a new role for calcium ion (Ca2+) signalling in eukaryotes, for phosphate sensing, which has not previously been described.

Marine diatoms under the light microscope. 

Diatoms are responsible for 20% of global primary productivity, equivalent to that of terrestrial rainforests combined. The work showed that phosphorus-starved diatoms used Ca2+-dependent signalling to perceive and coordinate rapid recovery responses to phosphorus resupply. The researchers also demonstrated that one of the first adaptations to phosphorus resupply is substantial enhancement of the uptake of another essential nutrient, nitrogen.

This rapid crosstalk between phosphorus and nitrogen metabolism, coordinated by the novel phosphorus-Ca2+ signalling pathway, enhances diatom competition for two critical nutrients. As major bloom formers, this work provides vital insight into how diatoms are so successful in rapidly responding to environmental cues such as nutrient supply, to dominate algal bloom formation.

Diatom P-Ca2+ signalling coordinates rapid recovery responses from P limitation. 

Dr. Katherine Helliwell, first author and a NERC Independent Research Fellow at the MBA and the University of Exeter, said “this work provides important new insight into how one of the most abundant marine phytoplankton groups is able to thrive in feast-famine nutrient regimes. Our study helps us to understand the cellular mechanisms employed by diatoms at the very early stages of bloom formation.”

Dr. Katherine Helliwell in the Marine Biological Association's culture collection. 

As diatoms sustain coastal fish populations and marine food webs, gaining understanding of what drives the ecological success of diatoms is important to all of us, especially those who enjoy the pleasures of coastal ecosystems, from swimming in the sea, to eating fish and seafood. The Helliwell Group studies environmental drivers regulating phytoplankton productivity, from understanding environmental signalling mechanisms to exploring the interactions between microbes, and their impact on marine microbial communities.

[1] Helliwell K. E., Harrison E., Christie-Oleza J., Downe J., Rees A., Kleiner F., Gaikwad T., Downe J., Al-Moosawi L, Aguilo-Ferretjans M., Brownlee C., Wheeler G. (2020) A novel Ca2+ signalling pathway co-ordinates environmental phosphorus sensing and nitrogen metabolism in marine diatoms, Current Biology, available at: 
Dec 14, 2020 By loiflo