The pennate diatom Pseudo‐nitzschia multistriata as a model for diatom life cycles, from the laboratory to the sea

Abstract

Phytoplankton dynamics are regulated by external cues, such as light and nutrients, as well as by biotic interactions and endogenous controls linked to life cycle characteristics. The planktonic pennate diatom Pseudo‐nitzschia multistriata, with a heterothallic mating system with two opposite mating types (MTs), represents a model for the study of diatom life cycles. P. multistriata is a toxic species, able to produce the neurotoxin domoic acid. First described in Japan in 1993, it was detected at the long‐term monitoring station MareChiara (Gulf of Naples, Italy) in 1995. Since then, P. multistriata has been reported from several worldwide coastal sites. A large body of knowledge has been produced on its ecology, genetic diversity, and life cycle characteristics. The availability of these data, the ecological relevance of the Pseudo‐nitzschia genus, and its controllable life cycle with a short generation time made it an ideal species to develop a genetic model system for diatoms. To enable functional studies, a 59 Mb genome sequence and several transcriptomic data were produced, and genetic transformation was optimized. These tools allowed the discovery of the first mating‐type determining gene for diatoms. Gene expression studies and metabolomics analyses defined genes and molecules underpinning different phases of the process of sexual reproduction. This model system, developed to explore the genetics of diatom life cycles, offers the opportunity to parallel experimental observations in the laboratory using in situ meta‐omics analyses along space and time, empowering knowledge on the biology and ecology of the genus.

Multiannual patterns of genetic structure and mating type ratios highlight the complex bloom dynamics of a marine planktonic diatom

“…Sexual reproduction is required by P. multistriata to produce large cells and counteract the progressive miniaturization of cell size that follows vegetative cell division; if populations are constituted by only one mating type, sex cannot occur. The potential of the MPB approach to follow over time the genetic structure of natural populations, and the availability of genomic resources for this model diatom 21 , will hopefully allow to further address the questions that emerged from this study and understand the mechanisms that drive intraspecific genetic diversity at the micro-evolutionary scale.…”

“…The marine diatom Pseudo-nitzschia multistriata is regularly recorded in the Gulf of Naples (GoN; Tyrrhenian Sea, Mediterranean Sea) since 1995 20 . This species was selected as a model for genetic and genomic studies 21 because it has a distinctive sigmoid cell shape that allows clear identification in light microscopy, it does not present cryptic diversity 14 and produces the neurotoxin domoic acid responsible for Amnesic Shellfish Poisoning 22 , 23 . As in the majority of diatoms, the average cell size of a population gradually decreases following mitotic divisions and large sized initial cells are only produced during the sexual phase 24 .…”

Proteomic and Lipidomic Plasma Evaluations Reveal Biomarkers for Domoic Acid Toxicosis in California Sea Lions

“…Domoic acid is a naturally occurring toxin produced by the pennate diatom, Pseudo-nitzschia 1 , a harmful algal bloom that is increasing in frequency and extent along the U.S. west coast. 2 In birds and mammals, domoic acid acts as an excitotoxin, affecting the brain and causing permanent short-term memory loss, seizures, brain damage, and death in certain situations.…”

DNA methylation is linked to the monoallelic expression ofMRP3, a diatom mating type determining gene

“…Due to extensive background data, long-term observations and availability of molecular resources, including a sequenced genome (Basu et al, 2017) , the pennate diatom Pseudo-nitzschia multistriata is a suitable model to investigate the function of DNA methylation in sex onset and sex determination (Ferrante et al, 2023) . P. multistriata is a toxic species, able to produce the neurotoxin domoic acid (Bates et al, 2018) .…”