Crossed wires: diatom phosphate sensing mechanisms coordinate nitrogen metabolism.

Phytoplankton can encounter dynamic changes in their environment including fluctuating nutrient supply, and therefore require survival mechanisms to compete for such growth-limiting resources. Diatoms, single-celled eukaryotic microalgae, are typically first responders when crucial macronutrients phosphorus (P) and nitrogen (N) enter the marine environment and therefore must have tightly regulated nutrient sensory systems. While nutrient starvation responses have been described, comparatively little is known about diatom nutrient sensing mechanisms.

Channels of Evolution: Unveiling Evolutionary Patterns in Diatom Ca Signalling.

Diatoms are important primary producers in marine and freshwater environments, but little is known about the signalling mechanisms they use to detect changes in their environment. All eukaryotic organisms use Ca signalling to perceive and respond to environmental stimuli, employing a range of Ca-permeable ion channels to facilitate the movement of Ca across cellular membranes. We investigated the distribution of different families of Ca channels in diatom genomes, with comparison to other members of the stramenopile lineage.

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.

Cold-induced [Ca2+]cyt elevations function to support osmoregulation in marine diatoms.

Diatoms are a group of microalgae that are important primary producers in a range of open ocean, freshwater, and intertidal environments. The latter can experience substantial long- and short-term variability in temperature, from seasonal variations to rapid temperature shifts caused by tidal immersion and emersion. As temperature is a major determinant in the distribution of diatom species, their temperature sensory and response mechanisms likely have important roles in their ecological success.

Reduced H channel activity disrupts pH homeostasis and calcification in coccolithophores at low ocean pH.

Coccolithophores are major producers of ocean biogenic calcite, but this process is predicted to be negatively affected by future ocean acidification scenarios. Since coccolithophores calcify intracellularly, the mechanisms through which changes in seawater carbonate chemistry affect calcification remain unclear. Here we show that voltage-gated H+ channels in the plasma membrane of Coccolithus braarudii serve to regulate pH and maintain calcification under normal conditions but have greatly reduced activity in cells acclimated to low pH.

Regulation and integration of membrane transport in marine diatoms.

Diatoms represent one of the most successful groups of marine phytoplankton and are major contributors to ocean biogeochemical cycling. They have colonized marine, freshwater and ice environments and inhabit all regions of the World's oceans, from poles to tropics. Their success is underpinned by a remarkable ability to regulate their growth and metabolism during nutrient limitation and to respond rapidly when nutrients are available.

Spatiotemporal patterns of intracellular Ca signalling govern hypo-osmotic stress resilience in marine diatoms.

Diatoms are globally important phytoplankton that dominate coastal and polar-ice assemblages. These environments exhibit substantial changes in salinity over dynamic spatiotemporal regimes. Rapid sensory systems are vital to mitigate the harmful consequences of osmotic stress.

A Novel Ca Signaling Pathway Coordinates Environmental Phosphorus Sensing and Nitrogen Metabolism in Marine Diatoms.

Diatoms are a diverse and globally important phytoplankton group, responsible for an estimated 20% of carbon fixation on Earth. They frequently form spatially extensive phytoplankton blooms, responding rapidly to increased availability of nutrients, including phosphorus (P) and nitrogen (N). Although it is well established that diatoms are common first responders to nutrient influxes in aquatic ecosystems, little is known of the sensory mechanisms that they employ for nutrient perception.

A Novel Single-Domain Na-Selective Voltage-Gated Channel in Photosynthetic Eukaryotes.

The evolution of Na-selective four-domain voltage-gated channels (4D-Nas) in animals allowed rapid Na-dependent electrical excitability, and enabled the development of sophisticated systems for rapid and long-range signaling. While bacteria encode single-domain Na-selective voltage-gated channels (BacNa), they typically exhibit much slower kinetics than 4D-Nas, and are not thought to have crossed the prokaryote-eukaryote boundary. As such, the capacity for rapid Na-selective signaling is considered to be confined to certain animal taxa, and absent from photosynthetic eukaryotes.

Responses of a Newly Evolved Auxotroph of Chlamydomonas to B Deprivation.

The corrinoid B is synthesized only by prokaryotes yet is widely required by eukaryotes as an enzyme cofactor. Microalgae have evolved B dependence on multiple occasions, and we previously demonstrated that experimental evolution of the non-B-requiring alga in media supplemented with B generated a B-dependent mutant (hereafter metE7). This clone provides a unique opportunity to study the physiology of a nascent B auxotroph.

Alternative Mechanisms for Fast Na/Ca Signaling in Eukaryotes via a Novel Class of Single-Domain Voltage-Gated Channels.

Rapid Na/Ca-based action potentials govern essential cellular functions in eukaryotes, from the motile responses of unicellular protists, such as Paramecium [1, 2], to complex animal neuromuscular activity [3]. A key innovation underpinning this fundamental signaling process has been the evolution of four-domain voltage-gated Na/Ca channels (4D-Cas/Nas). These channels are widely distributed across eukaryote diversity [4], albeit several eukaryotes, including land plants and fungi, have lost voltage-sensitive 4D-Ca/Nas [5-7].

Cross-exchange of B-vitamins underpins a mutualistic interaction between Ostreococcus tauri and Dinoroseobacter shibae.

Ostreococcus tauri, a picoeukaryotic alga that contributes significantly to primary production in oligotrophic waters, has a highly streamlined genome, lacking the genetic capacity to grow without the vitamins thiamine (B) and cobalamin (B) Here we demonstrate that the B and B auxotrophy of O. tauri can be alleviated by co-culturing with a heterotrophic bacterial partner Dinoroseobacter shibae, a member of the Rhodobacteraceae family of alpha-proteobacteria, genera of which are frequently found associated with marine algae. D.

Quantitative proteomics of a B -dependent alga grown in coculture with bacteria reveals metabolic tradeoffs required for mutualism.

The unicellular green alga Lobomonas rostrata requires an external supply of vitamin B (cobalamin) for growth, which it can obtain in stable laboratory cultures from the soil bacterium Mesorhizobium loti in exchange for photosynthate. We investigated changes in protein expression in the alga that allow it to engage in this mutualism. We used quantitative isobaric tagging (iTRAQ) proteomics to determine the L.

Insights into the red algae and eukaryotic evolution from the genome of (Bangiophyceae, Rhodophyta).

(laver) belongs to an ancient group of red algae (Bangiophyceae), is harvested for human food, and thrives in the harsh conditions of the upper intertidal zone. Here we present the 87.7-Mbp haploid genome (65.

The roles of B vitamins in phytoplankton nutrition: new perspectives and prospects.

Contents 62 I. 62 II. 63 III.

Algae as nutritional and functional food sources: revisiting our understanding.

Global demand for macroalgal and microalgal foods is growing, and algae are increasingly being consumed for functional benefits beyond the traditional considerations of nutrition and health. There is substantial evidence for the health benefits of algal-derived food products, but there remain considerable challenges in quantifying these benefits, as well as possible adverse effects. First, there is a limited understanding of nutritional composition across algal species, geographical regions, and seasons, all of which can substantially affect their dietary value.

How mutualisms arise in phytoplankton communities: building eco-evolutionary principles for aquatic microbes.

Extensive sampling and metagenomics analyses of plankton communities across all aquatic environments are beginning to provide insights into the ecology of microbial communities. In particular, the importance of metabolic exchanges that provide a foundation for ecological interactions between microorganisms has emerged as a key factor in forging such communities. Here we show how both studies of environmental samples and physiological experimentation in the laboratory with defined microbial co-cultures are being used to decipher the metabolic and molecular underpinnings of such exchanges.

Cyanobacteria and Eukaryotic Algae Use Different Chemical Variants of Vitamin B12.

Eukaryotic microalgae and prokaryotic cyanobacteria are the major components of the phytoplankton. Determining factors that govern growth of these primary producers, and how they interact, is therefore essential to understanding aquatic ecosystem productivity. Over half of microalgal species representing marine and freshwater habitats require for growth the corrinoid cofactor B12, which is synthesized de novo only by certain prokaryotes, including the majority of cyanobacteria.

Role of riboswitches in gene regulation and their potential for algal biotechnology.

Riboswitches are regulatory elements in messenger RNA to which specific ligands can bind directly in the absence of proteins. Ligand binding alters the mRNA secondary structure, thereby affecting expression of the encoded protein. Riboswitches are widespread in prokaryotes, with over 20 different effector ligands known, including amino acids, cofactors, and Mg(2+) ions, and gene expression is generally regulated by affecting translation or termination of transcription.

Establishing Chlamydomonas reinhardtii as an industrial biotechnology host.

Microalgae constitute a diverse group of eukaryotic unicellular organisms that are of interest for pure and applied research. Owing to their natural synthesis of value-added natural products microalgae are emerging as a source of sustainable chemical compounds, proteins and metabolites, including but not limited to those that could replace compounds currently made from fossil fuels. For the model microalga, Chlamydomonas reinhardtii, this has prompted a period of rapid development so that this organism is poised for exploitation as an industrial biotechnology platform.

Fundamental shift in vitamin B12 eco-physiology of a model alga demonstrated by experimental evolution.

A widespread and complex distribution of vitamin requirements exists over the entire tree of life, with many species having evolved vitamin dependence, both within and between different lineages. Vitamin availability has been proposed to drive selection for vitamin dependence, in a process that links an organism's metabolism to the environment, but this has never been demonstrated directly. Moreover, understanding the physiological processes and evolutionary dynamics that influence metabolic demand for these important micronutrients has significant implications in terms of nutrient acquisition and, in microbial organisms, can affect community composition and metabolic exchange between coexisting species.

Unraveling vitamin B12-responsive gene regulation in algae.

Photosynthetic microalgae play a vital role in primary productivity and biogeochemical cycling in both marine and freshwater systems across the globe. However, the growth of these cosmopolitan organisms depends on the bioavailability of nutrients such as vitamins. Approximately one-half of all microalgal species requires vitamin B12 as a growth supplement.

Widespread decay of vitamin-related pathways: coincidence or consequence?

The advent of modern genomics has provided an unparalleled opportunity to consider the gene complement of an organism, and scrutinize metabolic pathways that are no longer active. This approach has led to an increasing number of reports of vitamin-associated pathway deterioration, with many indicating that independent gene-loss events of one or a few key genes have led to vitamin auxotrophy. Nonfunctional unitary pseudogenes belonging to these pathways are found in several species, demonstrating that these are recent evolutionary processes.

Insights into the evolution of vitamin B12 auxotrophy from sequenced algal genomes.

Vitamin B(12) (cobalamin) is a dietary requirement for humans because it is an essential cofactor for two enzymes, methylmalonyl-CoA mutase and methionine synthase (METH). Land plants and fungi neither synthesize or require cobalamin because they do not contain methylmalonyl-CoA mutase, and have an alternative B(12)-independent methionine synthase (METE). Within the algal kingdom, approximately half of all microalgal species need the vitamin as a growth supplement, but there is no phylogenetic relationship between these species, suggesting that the auxotrophy arose multiple times through evolution.