Juan José Pierella Karlusich

FAS Division of Science, Harvard University

Oxidative stress and iron limitation represent the grim side of life in an oxygen-rich atmosphere. The versatile electron transfer shuttle ferredoxin, an iron-sulfur protein, is particularly sensitive to these hardships, and its down-regulation under adverse conditions severely compromises survival of phototrophs. Replacement of ferredoxin by a str...

Photosynthesis evolved in the ocean more than 2 billion years ago and is now performed by a wide range of evolutionarily distinct organisms, including both prokaryotes and eukaryotes. Our appreciation of their abundance, distributions, and contributions to primary production in the ocean has been increasing since they were first discovered in the s...

Key message Transcriptomes of solanaceous plants expressing a plastid-targeted antioxidant protein were analysed to identify chloroplast redox networks modulating the expression of nuclear genes associated with stress acclimation. Abstract Plastid functions depend on the coordinated expression of nuclear genes, many of them associated to developme...

Phytoplankton account for >45% of global primary production, and have an enormous impact on aquatic food webs and on the entire Earth System. Their members are found among prokaryotes (cyanobacteria) and multiple eukaryotic lineages containing chloroplasts. Genetic surveys of phytoplankton communities generally consist of PCR amplification of bacte...

Nitrogen fixation has a critical role in marine primary production, yet our understanding of marine nitrogen-fixers (diazotrophs) is hindered by limited observations. Here, we report a quantitative image analysis pipeline combined with mapping of molecular markers for mining >2,000,000 images and >1300 metagenomes from surface, deep chlorophyll max...

For decades, marine plankton have been investigated for their capacity to modulate biogeochemical cycles and provide fishery resources. Between the sunlit (epipelagic) layer and the deep dark waters, lies a vast and heterogeneous part of the ocean: the mesopelagic zone. How plankton composition is shaped by environment has been well-explored in the...

Aquatic life is strongly structured by the distribution of light which, besides attenuation in intensity, exhibits a continuous change in the spectrum with depth. The extent to which light changes are perceived by phytoplankton is largely unknown. By focusing on marine diatoms, we here provide the first in vivo quantitative assessment of responses...

The N2-fixing cyanobacterium Trichodesmium is an important player in the oceanic nitrogen and carbon cycles. Trichodesmium occurs both as single trichomes and as colonies containing hundreds of trichomes. In this review, we explore the benefits and disadvantages of colony formation, considering physical, chemical, and biological effects from nanome...

The rapid growth of diatoms makes them one of the most pervasive and productive types of plankton in the world's ocean, but the physiological basis for their high growth rates remains poorly understood. Here, we evaluate the factors that elevate diatom growth rates, relative to other plankton, using a steady-state metabolic flux model that computes...

Planète bleue, photosynthèse rouge et verte décrit les mécanismes qui permettent aux organismes photosynthétiques aquatiques de contribuer pour moitié à la productivité primaire nette, d’atténuer les changements climatiques en séquestrant le dioxyde de carbone et, par la production d’oxygène, d’avoir transformé l’atmosphère anoxique originelle de l...

Aquatic life is strongly structured by light gradients, with gradual decrease in light intensity and differential attenuation of sunlight wavelengths with depth. How phytoplankton perceive these variations is unknown. By providing the first in vivo quantitative assessment of the action of marine diatom phytochrome photoreceptors (DPH), we show that...

Microbial communities in the world ocean are affected strongly by oceanic circulation, creating characteristic marine biomes. The high connectivity of most of the ocean makes it difficult to disentangle selective retention of colonizing genotypes (with traits suited to biome specific conditions) from evolutionary selection, which would act on found...

Ocean color remote sensing offers two decades-long time series of information on phytoplankton abundance. However , determining the structure of the phytoplankton community from this signal is not straightforward, and many uncertainties remain to be evaluated, despite multiple intercomparison efforts of the different available algorithms. Here, we...

The Southwest Atlantic Ocean (SWAO) is a spatially dynamic region with a remarkably high primary productivity. An exhaustive identification of the members of its phytoplankton community is a key step to understand the processes that sustain this ecosystem. Here, we provide a community composition analysis of eukaryotic phytoplankton in four SWAO se...

Organic carbon fixed through the Calvin Cycle can be diverted towards different metabolic fates within and beyond the plastids of photosynthetic eukaryotes. These include export to the cytoplasm and mitochondrial respiration; gluconeogenesis of storage compounds; and the anabolic synthesis of lipids, amino acids and cofactors via the plastidial pyr...

The Southwest Atlantic Ocean (SWAO) is a spatially dynamic region with a remarkably high primary productivity. An exhaustive identification of the members of its phytoplankton community is a key step to understand the processes that sustain this ecosystem. Here, we provide a community composition analysis of eukaryotic phytoplankton in four SWAO se...

Microbial communities have essential roles in ocean ecology and planetary health. Microbes participate in nutrient cycles, remove huge quantities of carbon dioxide from the air and support ocean food webs. The taxonomic and functional diversity of the global ocean microbiome has been revealed by technological advances in sampling, DNA sequencing an...

A major challenge in characterizing plankton communities is the collection, identification and quantification of samples in a time-efficient way. The classical manual microscopy counts are gradually being replaced by high throughput imaging and nucleic acid sequencing. DNA sequencing allows deep taxonomic resolution (including cryptic species) as w...

Almost half of photosynthesis on Earth occurs in marine and freshwater environments; hence, aquatic photosynthetic organisms have an enormous impact on food webs and on the biogeochemistry of the entire Earth System. In this chapter, the authors provide an overview of the main groups of aquatic photoautotrophs, exploring their complex evolutionary...

Standard niche modelling is based on probabilistic inference from organismal occurrence data but does not benefit yet from genome‐scale descriptions of these organisms. This study overcomes this shortcoming by proposing a new conceptual niche that resumes the whole metabolic capabilities of an organism. The so‐called metabolic niche resumes well‐kn...

Sedimentary ancient DNA (sedaDNA) analyses are increasingly used to reconstruct marine ecosystems. The majority of marine sedaDNA studies use a metabarcoding approach (extraction and analysis of specific DNA fragments of a defined length), targeting short taxonomic marker genes. Promising examples are 18S-V9 rRNA (~121–130 base pairs, bp) and diat-...

Circulating in the sunlit ocean Marine plankton, which lie at the base of oceanic food chains, drive global biogeochemical fluxes, and knowledge of their distribution is key to understanding the response of oceans to environmental changes. Sommeria-Klein et al . explored the patterns and drivers of biogeography in eukaryotic plankton using a probab...

Biological nitrogen fixation contributes significantly to marine primary productivity. The current view depicts few cyanobacterial diazotrophs as the main marine nitrogen fixers. Here, we used 891 Tara Oceans metagenomes derived from surface waters of five oceans and two seas to generate a manually curated genomic database corresponding to free-liv...

The Arctic Ocean is being impacted by warming temperatures, increasing freshwater and highly variable ice conditions. The microalgal communities underpinning Arctic marine food webs, once thought to be dominated by diatoms, include a phylogenetically diverse range of small algal species, whose biology remains poorly understood. Here, we present gen...

Standard niche modeling is based on probabilistic inference from organismal occurrence data but does not benefit yet from genome-scale descriptions of these organisms. This study overcomes this shortcoming by proposing a new conceptual niche that encompasses the whole metabolic capabilities of an organism. The so-called metabolic niche resumes well...

Phytoplankton account for >45% of global primary production, and have an enormous impact on aquatic food webs and on the entire Earth System. Their members are found among prokaryotes (cyanobacteria) and multiple eukaryotic lineages containing chloroplasts. Phytoplankton communities are generally studied by PCR amplification of bacterial (16S), nuc...

Biological nitrogen fixation is a major factor contributing to microbial primary productivity in the open ocean. The current view depicts a few cyanobacterial diazotrophs as the most relevant marine nitrogen fixers, whereas heterotrophic diazotrophs are more diverse and considered to have lower impacts on the nitrogen balance. Here, we used 891 Tar...

Marine diatoms, the most successful photoautotrophs in the ocean, efficiently sequester a significant part of atmospheric CO2 to the ocean interior through their participation in the biological carbon pump. However, it is poorly understood how marine diatoms fix such a considerable amount of CO2, which is vital information towards modeling their re...

Marine plankton mitigate anthropogenic greenhouse gases, modulate biogeochemical cycles, and provide fishery resources. Plankton is distributed across a stratified ecosystem of sunlit surface waters and a vast, though understudied, mesopelagic 'dark ocean'. In this study, we mapped viruses, prokaryotes, and pico-eukaryotes across 32 globally-distri...

The productivity of the ocean is largely dependent on iron availability, and marine phytoplankton have evolved sophisticated mechanisms to cope with chronically low iron levels in vast regions of the open ocean. By analyzing the metabarcoding data generated from the Tara Oceans expedition, we determined how the global distribution of the model mari...

Significance The ochrophytes are an ancient and important group of eukaryotic algae, including diatoms, the most important photosynthesisers in the modern ocean, and a wide range of other species. Throughout their history, ochrophytes have exchanged genes with bacteria and eukaryotes through horizontal gene transfer (HGT), diversifying their cell b...

Marine phytoplankton are believed to account for more than 45% of photosynthetic net primary production on Earth, and hence are at the base of marine food webs and have an enormous impact on the entire Earth system. Their members are found across many of the major clades of the tree of life, including bacteria (cyanobacteria) and multiple eukaryoti...

[ Now published in Nature Communications: https://doi.org/10.1038/s41467-021-24299-y ] Biological nitrogen fixation plays a critical role in marine primary production, yet, our understanding of marine N2-fixers (diazotrophs) is hindered by limited observations. Here, we developed a quantitative image analysis pipeline in concert with mapping of mo...

Water limitation represents the main environmental constraint affecting crop yield worldwide. Photosynthesis is a primary drought target, resulting in over-reduction of the photosynthetic electron transport chain and increased production of reactive oxygen species in plastids. Manipulation of chloroplast electron distribution by introducing alterna...

We investigated transcriptomic features of genes regulated by chloroplast redox poise through recombinant expression of a plastid-targeted antioxidant protein (i.e., a cyanobacterial flavodoxin (Fld)) in potato and tobacco leaves. We found an important contribution of reactive oxygen species and hormone action to these transcriptional changes. In a...

Water stress causes considerable yield loss in potato, usually considered a drought-sensitive crop. Photosynthesis is a primary target of abiotic stresses, and manipulation of photosynthetic electron distribution in chloroplasts by introducing the alternative electron carrier flavodoxin increased tolerance of model plants to multiple environmental...

Diatoms (Bacillariophyta), one of the most abundant and diverse groups of marine phytoplankton, respond rapidly to the supply of new nutrients, often out-competing other phytoplankton. Herein, we integrated analyses of the evolution, distribution and expression modulation of two gene families involved in diatom nitrogen uptake (DiAMT1 and DiNRT2),...

Predicting responses of plankton to variations in essential nutrients is hampered by limited in situ measurements, a poor understanding of community composition, and the lack of reference gene catalogs for key taxa. Iron is a key driver of plankton dynamics and, therefore, of global biogeochemical cycles and climate. To assess the impact of iron av...

The development of oxygenic photosynthesis by primordial cyanobacteria ~2.7 billion years ago led to major changes in the components and organization of photosynthetic electron transport to cope with the challenges of an oxygen-enriched atmosphere. We review herein, following the seminal contributions as reported by Jaganathan et al. (Functional ge...

List of tobacco genes belonging to clusters formed by Xcv responses exacerbated or ameliorated in the presence of Fld (Figure 5). Unigene ID and description, mapman pathway annotation, and FC (in log2 scale) for each of the four line/treatment comparisons are shown. The color code indicates statistical significance in induction (red; log2FC > 1 and...

List of tobacco genes belonging to clusters formed by Xcv-responsive genes, which were already primed by Fld in the absence of Xcv inoculation (Figure 6). Unigene ID and description, mapman pathway annotation, and FC (in log2 scale) for each of the four line/treatment comparisons are shown. The color code indicates statistical significance in induc...

List of tobacco genes belonging to clusters formed by Fld-regulated genes in which the effect of the flavoprotein was reverted by Xcv infection (Figure 7). Unigene ID and description, mapman pathway annotation, and FC (in log2 scale) for each of the four line/treatment comparisons are shown. The color code indicates statistical significance in indu...

List of tobacco genes with altered expression patterns in response to Xcv in pfla4-2 and/or WT leaves. Unigene ID and description, mapman pathway annotation and FC (in log2 scale) are shown. The color code indicates statistical significance in induction (red; log2FC > 1 and FDR < 0.05) or repression (green; log2FC < -1 and FDR < 0.05). Genes belong...

List of tobacco genes with altered expression patterns in response to Fld. Unigene ID and description, mapman pathway annotation and fold-change (FC; in log2 scale) are shown. The color code indicates statistical significance in induction (red; log2FC > 1 and FDR < 0.05) or repression (green; log2FC < -1 and FDR < 0.05). Genes belonging to various...

Primer sets used for qRT-PCR determinations.

List of tobacco genes belonging to clusters formed by Xcv-induced or Xcv-repressed genes independently of genotype (Figure 4). Unigene ID and description, mapman pathway annotation, and FC (in log2 scale) for each of the four line/treatment comparisons are shown. The color code indicates statistical significance in induction (red; log2FC > 1 and FD...

Non-host resistance is the most ample and durable form of plant resistance against pathogen infection. It includes induction of defense-associated genes, massive metabolic reprogramming, and in many instances, a form of localized cell death (LCD) at the site of infection, purportedly designed to limit the spread of biotrophic and hemibiotrophic mic...

La Tierra se encuentra en un proceso de cambio climático asociado a actividades antropogénicas. Los reportes de las últimas décadas generados por el Grupo Intergubernamental de Expertos sobre el Cambio Climático señalan una variación sostenida de diferentes parámetros ambientales, y las proyecciones a futuro indican que estas tendencias se mantendr...

Environmental stresses and nutrient limitation are the major causes for crop losses worldwide. Engineering strategies aimed at improving stress tolerance have mostly focused on overexpression of plant-endogenous genes belonging to molecular networks for stress perception or stress responses. Based on the stress responses observed in cyanobacteria a...

Ferredoxins are electron shuttles harbouring iron-sulfur clusters that connect multiple oxido-reductive pathways in organisms displaying different lifestyles. Some prokaryotes and algae express an isofunctional electron carrier, flavodoxin, which contains flavin mononucleotide as cofactor. Both proteins evolved in the anaerobic environment precedin...

Ferredoxins are electron shuttles harboring iron-sulfur clusters which participate in oxido-reductive pathways in organisms displaying very different lifestyles. Ferredoxin levels decline in plants and cyanobacteria exposed to environmental stress and iron starvation. Flavodoxin is an isofunctional flavoprotein present in cyanobacteria and algae (n...