The smallest angiosperm genomes may be the price for effective traps of bladderworts.

BACKGROUND: Species of the carnivorous family Lentibulariaceae exhibit the smallest genomes in flowering plants. We explored the hypothesis that their minute genomes result from the unique mitochondrial cytochrome c oxidase (COX) mutation. The mutation may boost mitochondrial efficiency, which is especially useful for suction-bladder traps of Utricularia, but also increase DNA-damaging reactive oxygen species, leading to genome shrinkage through deletion-biased DNA repair. We aimed to explore this mutation's impact on genome size, providing insights into genetic mutation roles in plant genome evolution under environmental pressures. METHODS: We compiled and measured genome and mean chromosome sizes for 127 and 67 species, respectively, representing all three genera (Genlisea, Pinguicula, and Utricularia) of Lentibulariaceae. We also isolated and analyzed COX sequences to detect the mutation. Through phylogenetic regressions and Ornstein-Uhlenbeck models of trait evolution, we assessed the impact of the COX mutation on the genome and chromosome sizes across the family. RESULTS: Our findings reveal significant correlations between the COX mutations and smaller genome and chromosome sizes. Specifically, species carrying the ancestral COX sequence exhibited larger genomes and chromosomes than those with the mutation. This evidence supports the notion that the COX mutation contributes to genome downsizing, with statistical analyses confirming a directional evolution towards smaller genomes in species harboring these mutations. CONCLUSIONS: Our study confirms that the COX mutation in Lentibulariaceae is associated with genome downsizing, likely driven by increased reactive oxygen species production and subsequent DNA damage requiring deletion-biased repair mechanisms. While boosting mitochondrial energy output, this genetic mutation compromises genome integrity and may potentially affect recombination rates, illustrating a complex trade-off between evolutionary advantages and disadvantages. Our results highlight the intricate processes by which genetic mutations and environmental pressures shape genome size evolution in carnivorous plants.

To Eat or Not to Eat: Novel Stable Isotope Models Reveal a Shift in Carnivory with Nutrient Availability for Aquatic Utricularia spp.

BACKGROUND AND AIMS: Freshwater nitrogen inputs are increasing globally, altering the structure and function of wetland ecosystems adapted to low nutrient conditions. Carnivorous wetland plants, Utricularia spp., are hypothesised to reduce their reliance on carnivory and increase their assimilation of environmental nutrients when the supply of ambient nutrients increases. Despite success in using stable isotope approaches to quantify carnivory of terrestrial carnivorous plants, quantifying carnivory of aquatic Utricularia requires improvement. METHODS: We developed stable isotope mixing models to quantify aquatic plant carnivory and used these models to measure dietary changes of three Utricularia species: Utricularia australis, U. gibba, and U. uliginosa in 11 wetlands across a 794 km gradient in eastern Australia. Diet was assessed using multiple models that compared variations in the natural abundance nitrogen isotope composition (δ15N) of Utricularia spp. with that of non-carnivorous plants, and environmental and carnivorous nitrogen sources. KEY RESULTS: Carnivory supplied 40 - 100 % of plant nitrogen. The lowest carnivory rates coincided with the highest availability of ammonium and dissolved organic carbon. CONCLUSIONS: Our findings suggest that Utricularia populations may adapt to high nutrient environments by shifting away from energetically costly carnivory. This has implications for species conservation as anthropogenic impacts continue to affect global wetland ecosystems.

Shoots and Turions of Aquatic Plants as a Source of Fatty Acids.

BACKGROUND: Fatty acids are essential for human health. Currently, there is a search for alternative sources of fatty acids that could supplement such sources as staple crops or fishes. Turions of aquatic plants accumulate a variety of substances such as starch, free sugars, amino acids, reserve proteins and lipids. Our aim is to see if turions can be a valuable source of fatty acids. METHODS: Overwintering shoots and turions of aquatic carnivorous plants were collected. The plant material was extracted with hexane. The oils were analyzed using a gas chromatograph with mass spectrometer. RESULTS: The dominant compound in all samples was linolenic acid. The oil content was different in turions and shoots. The oil content of the shoots was higher than that of the turions, but the proportion of fatty acids in the oils from the shoots was low in contrast to the oils from the turions. The turions of Utricularia species were shown to be composed of about 50% fatty acids. CONCLUSIONS: The turions of Utricularia species can be used to obtain oil with unsaturated fatty acids. In addition, the high fatty acid content of turions may explain their ability to survive at low temperatures.

Laboratory scale evaluation of the feasibility of locally found bladderworts as biological agents to control dengue vector, Aedes aegypti in Sri Lanka.

BACKGROUND: The carnivorous genus Utricularia also includes aquatic species that have the potential to trap a wide range of prey, leading its death due to anoxia. However, the effectiveness of such an approach with carnivorous plants for vector control has not been evaluated in Sri Lanka. METHODS: Early instar (i & ii) and late instar (iii & iv) larvae of Aedes aegypti were exposed to locally found bladderwort (U. aurea Lour and Utricularia sp.). The experimental design was set with 10 larvae (both early and late instars separately) in 250 mL of water with bladderworts containing approximately 100 bladders in plant segments of both species, separately. Each treatment and control were repeated 50 times. The survival status of larvae was recorded daily until death or adult emergence. The larvae found whole or partially inside the bladders were attributed to direct predation. The Cox-regression model and Mantel-Cox log rank test were carried out to assess the survival probabilities of larvae in the presence of two bladderworts separately. RESULTS: The highest predation was observed when using early instar larvae in both U. aurea (97.8%) and Utricularia sp. (83.8%). The mortality caused due to predation by U. aurea was observed to be significantly higher according to the Mantel-Cox log-rank test (HR = 60.71, CI; 5.69-999.25, P = 0.004). The mortality rates of late instar stages of Ae. aegypti were observed to be lower in both U. aurea (82.6%) and Utricularia sp. (74.8%). Overall, the highest predation efficacy was detected from U. aurea (HR = 45.02; CI: 5.96-850.51, P = 0.017) even in late instar stages. The results suggested the cumulative predation in both plants on Ae. aegypti larvae was > 72%. CONCLUSIONS: Utricularia aurea is a competent predator of Ae. aegypti larvae. Further, it is recommended to evaluate the feasibility of this plant to be used in the field as a control intervention in integrated vector management programmes.

Cytokinins and auxins in organs of aquatic carnivorous plants: what do they reflect?

BACKGROUND AND AIMS: Aquatic carnivorous plants have typical rootless linear shoots bearing traps and exhibit steep physiological polarity with rapid apical growth. The aim was to analyse auxin and cytokinin metabolites in traps, leaves/shoots and shoot apices in several species of genera Aldrovanda and Utricularia to elucidate how the hormonal profiles reflect the specific organ functions and polarity. METHODS: The main auxin and cytokinin metabolites were analysed in miniature samples (>2 mg dry weight) of different organs of Aldrovanda vesiculosa and six Utricularia species using ultraperformance liquid chromatography coupled with triple quadrupole mass spectrometry. KEY RESULTS: Total contents of biologically active forms (free bases, ribosides) of all four main endogenously occurring cytokinin types were consistently higher in traps than in leaves in four Utricularia species with monomorphic shoots and/or higher than in shoots in two Utricularia species with dimorphic shoots. In Aldrovanda traps, the total content of different cytokinin forms was similar to or lower than that in shoots. In U. australis leaves, feeding on prey increased all cytokinin forms, while no consistent differences occurred in Aldrovanda. In four aquatic Utricularia species with monomorphic shoots, the content of four auxin forms was usually higher in traps than in leaves. Zero IAA content was determined in U. australis leaves from a meso-eutrophic site or when prey-fed. CONCLUSIONS: Different cytokinin and auxin profiles estimated in traps and leaves/shoots of aquatic carnivorous plants indicate an association with different dominant functions of these organs: nutrient uptake by traps versus photosynthetic function of traps. Interplay of cytokinins and auxins regulates apical dominance in these plants possessing strong polarity.

Expansin gene loss is a common occurrence during adaptation to an aquatic environment.

Expansins comprise a superfamily of plant cell wall loosening proteins that can be divided into four individual families (EXPA, EXPB, EXLA and EXLB). Aside from inferred roles in a variety of plant growth and developmental traits, little is known regarding the function of specific expansin clades, for which there are at least 16 in flowering plants (angiosperms); however, there is evidence to suggest that some expansins have cell-specific functions, in root hair and pollen tube development, for example. Recently, two duckweed genomes have been sequenced (Spirodela polyrhiza strains 7498 and 9509), revealing significantly reduced superfamily sizes. We hypothesized that there would be a correlation between expansin loss and morphological reductions seen among highly adapted aquatic species. In order to provide an answer to this question, we characterized the expansin superfamilies of the greater duckweed Spirodela, the marine eelgrass Zostera marina and the bladderwort Utricularia gibba. We discovered rampant expansin gene and clade loss among the three, including a complete absence of the EXLB family and EXPA-VII. The most convincing correlation between morphological reduction and expansin loss was seen for Utricularia and Spirodela, which both lack root hairs and the root hair expansin clade EXPA-X. Contrary to the pattern observed in other species, four Utricularia expansins failed to branch within any clade, suggesting that they may be the result of neofunctionalization. Last, an expansin clade previously discovered only in eudicots was identified in Spirodela, allowing us to conclude that the last common ancestor of monocots and eudicots contained a minimum of 17 expansins.

Bladderworts, the smallest known suction feeders, generate inertia-dominated flows to capture prey.

Aquatic bladderworts (Utricularia gibba and U. australis) capture zooplankton in mechanically triggered underwater traps. With characteristic dimensions less than 1 mm, the trapping structures are among the smallest known to capture prey by suction, a mechanism that is not effective in the creeping-flow regime where viscous forces prevent the generation of fast and energy-efficient suction flows. To understand what makes suction feeding possible on the small scale of bladderwort traps, we characterised their suction flows experimentally (using particle image velocimetry) and mathematically (using computational fluid dynamics and analytical mathematical models). We show that bladderwort traps avoid the adverse effects of creeping flow by generating strong, fast-onset suction pressures. Our findings suggest that traps use three morphological adaptations: the trap walls' fast release of elastic energy ensures strong and constant suction pressure; the trap door's fast opening ensures effectively instantaneous onset of suction; the short channel leading into the trap ensures undeveloped flow, which maintains a wide effective channel diameter. Bladderwort traps generate much stronger suction flows than larval fish with similar gape sizes because of the traps' considerably stronger suction pressures. However, bladderworts' ability to generate strong suction flows comes at considerable energetic expense.

The Ability of Tetrahymena utriculariae (Ciliophora, Oligohymenophorea) to Colonize Traps of Different Species of Aquatic Carnivorous Utricularia.

The host specificity of the recently described ciliate species Tetrahymena utriculariae was tested in a greenhouse growth experiment, which included 14 different species of aquatic Utricularia as potential host plants. We confirmed the high specificity of the interaction between U. reflexa and T. utriculariae, the former being the only tested host species able to maintain colonization for prolonged time periods. We conclude that this plant-microbe relationship is a unique and specialized form of digestive mutualism and the plant-microbe unit a suitable experimental system for future ecophysiological studies.

Long-read sequencing uncovers the adaptive topography of a carnivorous plant genome.

Utricularia gibba, the humped bladderwort, is a carnivorous plant that retains a tiny nuclear genome despite at least two rounds of whole genome duplication (WGD) since common ancestry with grapevine and other species. We used a third-generation genome assembly with several complete chromosomes to reconstruct the two most recent lineage-specific ancestral genomes that led to the modern U. gibba genome structure. Patterns of subgenome dominance in the most recent WGD, both architectural and transcriptional, are suggestive of allopolyploidization, which may have generated genomic novelty and led to instantaneous speciation. Syntenic duplicates retained in polyploid blocks are enriched for transcription factor functions, whereas gene copies derived from ongoing tandem duplication events are enriched in metabolic functions potentially important for a carnivorous plant. Among these are tandem arrays of cysteine protease genes with trap-specific expression that evolved within a protein family known to be useful in the digestion of animal prey. Further enriched functions among tandem duplicates (also with trap-enhanced expression) include peptide transport (intercellular movement of broken-down prey proteins), ATPase activities (bladder-trap acidification and transmembrane nutrient transport), hydrolase and chitinase activities (breakdown of prey polysaccharides), and cell-wall dynamic components possibly associated with active bladder movements. Whereas independently polyploid Arabidopsis syntenic gene duplicates are similarly enriched for transcriptional regulatory activities, Arabidopsis tandems are distinct from those of U. gibba, while still metabolic and likely reflecting unique adaptations of that species. Taken together, these findings highlight the special importance of tandem duplications in the adaptive landscapes of a carnivorous plant genome.

Picky carnivorous plants? Investigating preferences for preys' trophic levels - a stable isotope natural abundance approach with two terrestrial and two aquatic Lentibulariaceae tested in Central Europe.

BACKGROUND AND AIMS: Stable isotope two-source linear mixing models are frequently used to calculate the nutrient-uptake efficiency of carnivorous plants from pooled prey. This study aimed to separate prey into three trophic levels as pooled prey limits statements about the contribution of a specific trophic level to the nutrition of carnivorous plants. Phytoplankton were used as an autotrophic reference for aquatic plants as the lack of suitable reference plants impedes calculation of their efficiency. METHODS: Terrestrial (Pinguicula) and aquatic (Utricularia) carnivorous plants alongside autotrophic reference plants and potential prey from six sites in Germany and Austria were analysed for their stable isotope natural abundances (δ15N, δ13C). A two-source linear mixing model was applied to calculate the nutrient-uptake efficiency of carnivorous plants from pooled prey. Prey preferences were determined using a Bayesian inference isotope mixing model. KEY RESULTS: Phytophagous prey represented the main contribution to the nutrition of Pinguicula (approx. 55 %), while higher trophic levels contributed a smaller amount (diverse approx. 27 %, zoophagous approx. 17 %). As well as around 48 % nitrogen, a small proportion of carbon (approx. 9 %) from prey was recovered in the tissue of plants. Aquatic Utricularia australis received 29 % and U. minor 21 % nitrogen from zooplankton when applying phytoplankton as the autotrophic reference. CONCLUSIONS: The separation of prey animals into trophic levels revealed a major nutritional contribution of lower trophic level prey (phytophagous) for temperate Pinguicula species. Naturally, prey of higher trophic levels (diverse, zoophagous) are rarer, resulting in a smaller chance of being captured. Phytoplankton represents an adequate autotrophic reference for aquatic systems to estimate the contribution of zooplankton-derived nitrogen to the tissue of carnivorous plants. The autonomous firing of Utricularia bladders results in the additional capture of phytoplankton, calling for new aquatic references to determine the nutritional importance of phytoplankton for aquatic carnivorous plants.

Intraspecific Variation within the Utricularia amethystina Species Morphotypes Based on Chloroplast Genomes.

Utricularia amethystina Salzm. ex A.St.-Hil. & Girard (Lentibulariaceae) is a highly polymorphic carnivorous plant taxonomically rearranged many times throughout history. Herein, the complete chloroplast genomes (cpDNA) of three U. amethystina morphotypes: purple-, white-, and yellow-flowered, were sequenced, compared, and putative markers for systematic, populations, and evolutionary studies were uncovered. In addition, RNA-Seq and RNA-editing analysis were employed for functional cpDNA evaluation. The cpDNA of three U. amethystina morphotypes exhibits typical quadripartite structure. Fine-grained sequence comparison revealed a high degree of intraspecific genetic variability in all morphotypes, including an exclusive inversion in the psbM and petN genes in U. amethystina yellow. Phylogenetic analyses indicate that U. amethystina morphotypes are monophyletic. Furthermore, in contrast to the terrestrial Utricularia reniformis cpDNA, the U. amethystina morphotypes retain all the plastid NAD(P)H-dehydrogenase (ndh) complex genes. This observation supports the hypothesis that the ndhs in terrestrial Utricularia were independently lost and regained, also suggesting that different habitats (aquatic and terrestrial) are not related to the absence of Utricularia ndhs gene repertoire as previously assumed. Moreover, RNA-Seq analyses recovered similar patterns, including nonsynonymous RNA-editing sites (e.g., rps14 and petB). Collectively, our results bring new insights into the chloroplast genome architecture and evolution of the photosynthesis machinery in the Lentibulariaceae.

Molecular phylogeny of bladderworts: A wide approach of Utricularia (Lentibulariaceae) species relationships based on six plastidial and nuclear DNA sequences.

The carnivorous plant genus Utricularia L. (bladderwort) comprises about 240 species distributed worldwide and is traditionally classified into two subgenera (Polypompholyx and Utricularia) and 35 sections, based mainly on general and trap morphology. It is one out of the largest carnivorous genera, representing ca. 30% of all carnivorous plant species, and is also the most widely distributed. According to previous phylogenetic studies, most infrageneric sections are monophyletic, but there are several incongruences considering their relationships and also the dissenting position of some species as a result of a too few (mostly one or two) molecular markers analyzed. Thus, here we present a multilocus phylogeny for Utricularia species with a wide taxonomic sampling (78 species and 115 accessions) based on six plastid (rbcL, matK, rpl20-rps12, rps16, trnL-F) and nuclear DNA (ITS region) sequences. The aim is to reconstruct a well-resolved tree to propose evolutionary and biogeographic hypotheses for the radiation of lineages with inferences about the divergence times of clades using a molecular clock approach.

Phylogeny of the 'orchid-like' bladderworts (gen. Utricularia sect. Orchidioides and Iperua: Lentibulariaceae) with remarks on the stolon-tuber system.

Background and Aims: The 'orchid-like' bladderworts ( Utricularia ) comprise 15 species separated into two sections: Orchidioides and Iperua . These robust and mostly epiphytic species were originally grouped within the section Orchidioides by the first taxonomical systems. These species were later split into two sections when sect. Iperua was proposed. Due to the lack of strong evidence based on a robust phylogenetic perspective, this study presents a phylogenetic proposal based on four different DNA sequences (plastid and nuclear) and morphology to test the monophyly of the two sections. Methods: In comparison with all previous phylogenetic studies, the largest number of species across the sections was covered: 11 species from sections Orchidioides and Iperua with 14 species as an external group. Maximum likelihood and Bayesian inferences were applied to DNA sequences of rps16 , trnL-F , matK , the internal transcribed spacer (ITS) and three morphological characters: (1) the crest of the corolla; (2) the primary organs in the embryo; and (3) tubers. Additionally, a histochemical analysis of the stolons and tubers is presented from an evolutionary perspective. Key Results: The analyses showed the paraphyly of sect. Iperua , since Utricularia humboldtii is more related to the clade of sect. Orchidioides . Utricularia cornigera is grouped in the sect. Iperua clade based on chloroplast DNA sequences, but it is nested to sect. Orchidioides according to ITS dataset. Morphological characters do not support the breaking up of the 'orchid-like' species into two sections, either. Moreover, the stolon-tuber systems of both sections serve exclusively for water storage, according to histological analyses. Conclusions: This study provides strong evidence, based on DNA sequences from two genomic compartments (plastid and nucleus) and morphology to group the Utricularia sect. Orchidioides into the sect. Iperua . The tubers are important adaptations for water storage and have been derived from stolons at least twice in the phylogenetic history of 'orchid-like' bladderworts.

The Green Tetrahymena utriculariae n. sp. (Ciliophora, Oligohymenophorea) with Its Endosymbiotic Algae (Micractinium sp.), Living in Traps of a Carnivorous Aquatic Plant.

The genus Tetrahymena (Ciliophora, Oligohymenophorea) probably represents the best studied ciliate genus. At present, more than forty species have been described. All are colorless, i.e. they do not harbor symbiotic algae, and as aerobes they need at least microaerobic habitats. Here, we present the morphological and molecular description of the first green representative, Tetrahymena utriculariae n. sp., living in symbiosis with endosymbiotic algae identified as Micractinium sp. (Chlorophyta). The full life cycle of the ciliate species is documented, including trophonts and theronts, conjugating cells, resting cysts and dividers. This species has been discovered in an exotic habitat, namely in traps of the carnivorous aquatic plant Utricularia reflexa (originating from Okavango Delta, Botswana). Green ciliates live as commensals of the plant in this anoxic habitat. Ciliates are bacterivorous, however, symbiosis with algae is needed to satisfy cell metabolism but also to gain oxygen from symbionts. When ciliates are cultivated outside their natural habitat under aerobic conditions and fed with saturating bacterial food, they gradually become aposymbiotic. Based on phylogenetic analyses of 18S rRNA and mitochondrial cox1 genes T. utriculariae forms a sister group to Tetrahymena thermophila.

Ecological Traits of the Algae-Bearing Tetrahymena utriculariae (Ciliophora) from Traps of the Aquatic Carnivorous Plant Utricularia reflexa.

Trap fluid of aquatic carnivorous plants of the genus Utricularia hosts specific microbiomes consisting of commensal pro- and eukaryotes of largely unknown ecology. We examined the characteristics and dynamics of bacteria and the three dominant eukaryotes, i.e. the algae-bearing ciliate Tetrahymena utriculariae (Ciliophora), a green flagellate Euglena agilis (Euglenophyta), and the alga Scenedesmus alternans (Chlorophyta), associated with the traps of Utricularia reflexa. Our study focused on ecological traits and life strategies of the highly abundant ciliate whose biomass by far exceeds that of other eukaryotes and bacteria independent of the trap age. The ciliate was the only bacterivore in the traps, driving rapid turnover of bacterial standing stock. However, given the large size of the ciliate and the cell-specific uptake rates of bacteria we estimated that bacterivory alone would likely be insufficient to support its apparent rapid growth in traps. We suggest that mixotrophy based on algal symbionts contributes significantly to the diet and survival strategy of the ciliate in the extreme (anaerobic, low pH) trap-fluid environment. We propose a revised concept of major microbial interactions in the trap fluid where ciliate bacterivory plays a central role in regeneration of nutrients bound in rapidly growing bacterial biomass.

Cytokinin, auxin and physiological polarity in the aquatic carnivorous plants Aldrovanda vesiculosa and Utricularia australis.

BACKGROUND AND AIMS: The typical rootless linear shoots of aquatic carnivorous plants exhibit clear, steep polarity associated with very rapid apical shoot growth. The aim of this study was to determine how auxin and cytokinin contents are related to polarity and shoot growth in such plants. METHODS: The main auxin and cytokinin metabolites in separated shoot segments and turions of two carnivorous plants, Aldrovanda vesiculosa and Utricularia australis, were analysed using ultra-high-performance liquid chromatography coupled with triple quad mass spectrometry. KEY RESULTS: In both species, only isoprenoid cytokinins were identified. Zeatin cytokinins predominated in the apical parts, with their concentrations decreasing basipetally, and the trans isomer predominated in A. vesiculosa whereas the cis form was more abundant in U australis. Isopentenyladenine-type cytokinins, in contrast, increased basipetally. Conjugated cytokinin metabolites, the O-glucosides, were present at high concentrations in A. vesiculosa but only in minute amounts in U. australis. N(9)-glucoside forms were detected only in U. australis, with isopentenyladenine-9-glucoside (iP9G) being most abundant. In addition to free indole-3-acetic acid (IAA), indole-3-acetamide (IAM), IAA-aspartate (IAAsp), IAA-glutamate (IAGlu) and IAA-glycine (IAGly) conjugates were identified. CONCLUSIONS: Both species show common trends in auxin and cytokinin levels, the apical localization of the cytokinin biosynthesis and basipetal change in the ratio of active cytokinins to auxin, in favour of auxin. However, our detailed study of cytokinin metabolic profiles also revealed that both species developed different regulatory mechanisms of active cytokinin content; on the level of their degradation, in U. australis, or in the biosynthesis itself, in the case of A. vesiculosa Results indicate that the rapid turnover of these signalling molecules along the shoots is essential for maintaining the dynamic balance between the rapid polar growth and development of the apical parts and senescence of the older, basal parts of the shoots.

Capture of algae promotes growth and propagation in aquatic Utricularia.

BACKGROUND AND AIMS: Some carnivorous plants trap not only small animals but also algae and pollen grains. However, it remains unclear if these trapped particles are useless bycatch or whether they provide nutrients for the plant. The present study examines this question in Utricularia, which forms the largest and most widely spread genus of carnivorous plants, and which captures prey by means of sophisticated suction traps. METHODS: Utricularia plants of three different species (U. australis, U. vulgaris and U. minor) were collected in eight different water bodies including peat bogs, lakes and artificial ponds in three regions of Austria. The prey spectrum of each population was analysed qualitatively and quantitatively, and correlated with data on growth and propagation, C/N ratio and δ(15)N. KEY RESULTS: More than 50 % of the prey of the Utricularia populations investigated consisted of algae and pollen, and U. vulgaris in particular was found to capture large amounts of gymnosperm pollen. The capture of algae and pollen grains was strongly correlated with most growth parameters, including weight, length, budding and elongation of internodes. The C/N ratio, however, was less well correlated. Other prey, such as moss leaflets, fungal hyphae and mineral particles, were negatively correlated with most growth parameters. δ(15)N was positively correlated with prey capture, but in situations where algae were the main prey objects it was found that the standard formula for calculation of prey-derived N was no longer applicable. CONCLUSIONS: The mass capture of immotile particles confirms the ecological importance of autonomous firing of the traps. Although the C/N ratio was little influenced by algae, they clearly provide other nutrients, possibly including phosphorus and trace elements. By contrast, mosses, fungi and mineral particles appear to be useless bycatch. Correlations with chemical parameters indicate that Utricularia benefits from nutrient-rich waters by uptake of inorganic nutrients from the water, by the production of more traps per unit of shoot length, and by the capture of more prey particles per trap, as nutrient-rich waters harbour more prey organisms.

Dinitrogen fixation associated with shoots of aquatic carnivorous plants: is it ecologically important?

BACKGROUND AND AIMS: Rootless carnivorous plants of the genus Utricularia are important components of many standing waters worldwide, as well as suitable model organisms for studying plant-microbe interactions. In this study, an investigation was made of the importance of microbial dinitrogen (N2) fixation in the N acquisition of four aquatic Utricularia species and another aquatic carnivorous plant, Aldrovanda vesiculosa. METHODS: 16S rRNA amplicon sequencing was used to assess the presence of micro-organisms with known ability to fix N2. Next-generation sequencing provided information on the expression of N2 fixation-associated genes. N2 fixation rates were measured following (15)N2-labelling and were used to calculate the plant assimilation rate of microbially fixed N2. KEY RESULTS: Utricularia traps were confirmed as primary sites of N2 fixation, with up to 16 % of the plant-associated microbial community consisting of bacteria capable of fixing N2. Of these, rhizobia were the most abundant group. Nitrogen fixation rates increased with increasing shoot age, but never exceeded 1·3 µmol N g(-1) d. mass d(-1). Plant assimilation rates of fixed N2 were detectable and significant, but this fraction formed less than 1 % of daily plant N gain. Although trap fluid provides conditions favourable for microbial N2 fixation, levels of nif gene transcription comprised <0·01 % of the total prokaryotic transcripts. CONCLUSIONS: It is hypothesized that the reason for limited N2 fixation in aquatic Utricularia, despite the large potential capacity, is the high concentration of NH4-N (2·0-4·3 mg L(-1)) in the trap fluid. Resulting from fast turnover of organic detritus, it probably inhibits N2 fixation in most of the microorganisms present. Nitrogen fixation is not expected to contribute significantly to N nutrition of aquatic carnivorous plants under their typical growth conditions; however, on an annual basis the plant-microbe system can supply nitrogen in the order of hundreds of mg m(-2) into the nutrient-limited littoral zone, where it may thus represent an important N source.

Corrigendum: Mining the Utricularia gibba genome for insulator-like elements for genetic engineering.

[This corrects the article DOI: 10.3389/fpls.2023.1279231.].

Evaluating the carnivorous efficacy of Utricularia aurea (Lamiales: Lentibulariaceae) on the larval stages of Anopheles stephensi, Culex quinquefasciatus, and Aedes aegypti (Diptera: Culicidae).

The emergence of insecticide resistance in mosquitoes necessitates the exploration and validation of sustainable biological strategies for controlling mosquitoes in their natural habitats. We assessed the predatory effect of Utricularia aurea Lour (Lamiales: Lentibulariaceae), an aquatic carnivorous plant found in the Indian subcontinent, Japan, and Australia, on 4 instars of Anopheles stephensi Liston, Culex quinquefasciatus Say, and Aedes aegypti Linn (Diptera: Culicidae), in the laboratory and field settings. In the laboratory setting, predation of larvae by U. aurea was highest during the first hour when it predated 45%, 61%, and 58% of first instars of An. stephensi, Cx. quinquefasciatus, and, Ae. aegypti, respectively, and, within 12 h, U. aurea preyed upon ~95% of the first, second, and third instars of the 3 mosquito species, ~80% of the fourth instars of An. stephensi and Ae. aegypti, and ~60% of fourth instars of Cx. quinquefasciatus. The predatory effect of U. aurea varied with mosquito species and instar. Broadly, predation risk declined with the increase of the instar size. In the field setting, at the end of 16 days, U. aurea predated 76% and 71% of the immature An. stephensi and Ae. aegypti, respectively. Our findings suggest U. aurea can be utilized as a potential biocontrol agent for controlling mosquito larvae in natural habitats; however, the current claim warrants additional investigations in a variety of natural habitats.