A Novel Ca2+ Signaling Pathway Coordinates Environmental Phosphorus Sensing and Nitrogen Metabolism in Marine Diatoms

Abstract

Highlights d Phosphorus (P)-limited diatoms sense P via a Ca 2+dependent signaling pathway d P-Ca 2+ signaling is employed by representative centric and pennate diatom species d Rapid cross-talk with N metabolism mediates diatom recovery responses to P resupply d P-Ca 2+ signaling coordinates diatom recovery responses from P limitation

Chlamydomonas reinhardtii cellular compartments and their contribution to intracellular calcium signalling

“…As discussed in this section, an aequorin-based Ca 2+ sensor has already been used in P. tricornutum ; however, the development of transgenic lines, also stably expressing other novel GECIs in different subcellular compartments, could represent a useful tool to address the above-mentioned question in diatoms too. Examples relating to this are two recently published works in which the expression of the previously mentioned R-GECO1 in P. tricornutum and Thalassiosira pseudonana has allowed both the identification of a novel class of Na + - and Ca 2+ -permeable, voltage-gated channels, and the discovery of a Ca 2+ signalling pathway in diatoms to sense and rapidly respond to increases in phosphorus availability ( Helliwell et al , 2019 , 2021 ).…”

Diatom Ecophysiology: Crossing Signals on the Road to Recovery from Nutrient Deprivation

“…However, growth is a rather late-stage indicator of recovery, representing the integrated end product of the physiological and biochemical pathways that allow cells to capitalize when limiting resources become available. In this issue of Current Biology, a study by Helliwell et al 14 explores the molecular underpinnings of this rapid recovery response to P limitation in diatoms, documenting the existence of a novel Ca 2+ -based signaling pathway not previously described in eukaryotes that mediates the response to P resupply.…”

“…In the new study, Helliwell et al 14 provide the first glimpse into the earliest molecular response of diatoms to recovery from P limitation, even before growth resumption. Using the welldescribed model diatom Phaeodactylum tricornutum transformed to express R-GECO1, a fluorescence-based sensor of intracellular Ca 2+ , the authors observed an increase in Ca 2+ within seconds following resupply of P to P-limited cultures (Figure 1).…”

“…Despite having diverged only 90 million years ago, the genomes of P. tricornutum and T. pseudonana share only 55% identity -less than that between humans and pufferfish, which are separated by 450 million years of evolutionary history 16 . Intriguingly, Helliwell et al 14 demonstrate that T. pseudonana also uses a Ca 2+ -based sensor to recover from P-limitation, highlighting the potential for a conserved response among diverse diatoms.…”

“…The new work by Helliwell et al 14 provides a framework for understanding how diatoms sense and respond to pulsed nutrients in the environment, while also highlighting the complexity of the molecular response required to recover from nutrient limitation. Although the role of Ca 2+ in the perception of environmental signals in diatoms is not new 17 , this is the first time a Ca 2+ -based pathway has been shown to play a role in jumpstarting diatoms out of P deprivation and back on the road to recovery, which involves repartitioning resources back to N uptake and assimilation to support protein and chlorophyll synthesis.…”