Neochloris aquatica induces larval mortality, molting defects, and unstable flightless adults in the Asian tiger mosquito.

The Asian tiger mosquito, Aedes albopictus, is a highly invasive and aggressive species capable of transmitting a large number of etiological agents of medical and veterinary importance, posing a high risk for the transmission of emerging viruses between animals and humans. In this work, we evaluated the mosquitocidal activity of Neochloris aquatica against A. albopictus throughout its development and analyzed whether this effect was potentiated when the microalga was cultivated under stress conditions due to nutrient deprivation. Our results suggest that N. aquatica produces metabolites that have negative effects on these insects, including larval mortality, interruption of pupal development, and incomplete emergence of adults when fed on microalgae in the larval stages. When microalgae were cultured under stress conditions, an increase in molting defects was recorded, and the number of healthy adults emerged drastically decreased. Histological studies revealed severe signs of total disintegration of different tissues and organs in the thorax and abdomen regions. The muscles and fat bodies in the midgut and foregut were severely distorted. In particular, larval intestinal tissue damage included vacuolization of the cytoplasm, destruction of brush border microvilli, and dilation of the intercellular space, which are distinctive morphological characteristics of apoptotic cells. Evidence suggests that N. aquatica produces metabolites with mosquitocidal effects that affect development and, therefore, the ability to vector etiological agents of medical and veterinary importance.

Hormone released by the microalgae Neochlorisaquatica and alkalinization influence growth of terrestrial and floating aquatic plants.

The microalgae Neochloris aquatica were previously evaluated as a potential biological control agent and source of bioactive compounds against immature stages of Culex quinquefasciatus. Larvae reared on microalgae suspension showed mortality or drastic effects with morphological alterations and damage in the midgut. N. aquatica have nutritional and toxic effects, resulting in delayed life cycle and incomplete adult development. Given the possibility of its use as a biological control agent, in this work we evaluate the effect of microalgae on other organisms of the environment, such as plants. Arabidopsis thaliana, a terrestrial plant, and Lemna sp., a floating aquatic plant, were selected as examples. Interaction assays and compound evaluations showed that the microalgae release auxins causing root inhibition, smaller epidermal cells and hairy root development. In Lemna sp., a slight decrease in growth rate was observed, with no deleterious effects on the fronds. On the other hand, we detected a detrimental effect on plants when interactions were performed in a closed environment, in a medium containing soluble carbonate, in which microalgae culture rapidly modifies the pH. The experiments showed that alkalinization of the medium inhibits plant growth, causing bleaching of leaves or fronds. This negative effect in plants was not observed when plants and microalgae were cultured in carbonate-free media. In conclusion, the results showed that N. aquatica can modify plant growth without being harmful, but the rapid alkalinization produced by carbon metabolism of microalgae under CO2-limiting conditions, could regulate the number of plants.

NIPK, a protein pseudokinase that interacts with the C subunit of the transcription factor NF-Y, is involved in rhizobial infection and nodule organogenesis.

Heterotrimeric Nuclear Factor Y (NF-Y) transcription factors are key regulators of the symbiotic program that controls rhizobial infection and nodule organogenesis. Using a yeast two-hybrid screening, we identified a putative protein kinase of Phaseolus vulgaris that interacts with the C subunit of the NF-Y complex. Physical interaction between NF-YC1 Interacting Protein Kinase (NIPK) and NF-YC1 occurs in the cytoplasm and the plasma membrane. Only one of the three canonical amino acids predicted to be required for catalytic activity is conserved in NIPK and its putative homologs from lycophytes to angiosperms, indicating that NIPK is an evolutionary conserved pseudokinase. Post-transcriptional silencing on NIPK affected infection and nodule organogenesis, suggesting NIPK is a positive regulator of the NF-Y transcriptional complex. In addition, NIPK is required for activation of cell cycle genes and early symbiotic genes in response to rhizobia, including NF-YA1 and NF-YC1. However, strain preference in co-inoculation experiments was not affected by NIPK silencing, suggesting that some functions of the NF-Y complex are independent of NIPK. Our work adds a new component associated with the NF-Y transcriptional regulators in the context of nitrogen-fixing symbiosis.

Culex quinquefasciatus larvae development arrested when fed on Neochloris aquatica.

Culex quinquefasciatus is a cosmopolitan species widely distributed in the tropical and subtropical areas of the world. Due to its long history of close association with humans, the transmission of arboviruses and parasites have an important role in veterinary and public health. Adult females feed mainly on birds although they can also feed on humans and other mammals. On the other hand, larvae are able to feed on a great diversity of microorganisms, including microalgae, present in natural or artificial breeding sites with a high organic load. These two particularities, mentioned above, are some of the reasons why this mosquito is so successful in the environment. In this work, we report the identification of a microalga found during field sampling in artificial breeding sites, in a group of discarded tires with accumulated rainwater. Surprisingly, only one of them had a bright green culture without mosquito larvae while the other surrounding tires contained a large number of mosquito larvae. We isolated and identified this microorganism as Neochloris aquatica, and it was evaluated as a potential biological control agent against Cx. quinquefasciatus. The oviposition site preference in the presence of the alga by gravid females, and the effects on larval development were analyzed. Additionally, microalga effect on Cx. quinquefasciatus wild type, naturally infected with the endosymbiotic bacterium Wolbachia (w+) and Wolbachia free (w-) laboratory lines was explored. According to our results, even though it is chosen by gravid females to lay their eggs, the microalga had a negative effect on the development of larvae from both populations. Additionally, when the larvae were fed with a culture of alga supplemented with balanced fish food used as control diet, they were not able to reverse its effect, and were unable to complete development until adulthood. Here, N. aquatica is described as a biological agent, and as a potential source of bioactive compounds for the control of mosquito populations important in veterinary and human health.

Developmental plasticity in Arabidopsis thaliana under combined cold and water deficit stresses during flowering stage.

MAIN CONCLUSION: Morpho-physiological changes were observed in Arabidopsis plants acclimated to long-term combined cold and water deficit stresses. Limiting growth and differences in bolting, flowering, and silique development were evidenced. In nature, plants are exposed to multiple and simultaneous abiotic stresses that influence their growth, development, and reproduction. In the last years, the study of combined stresses has aroused the interest to know the physiological and molecular responses, because these new stress conditions are probed to be different from the sum of the individual stress. We are interested in the study of the acclimation of plants growing under the combination of cold and water deficit stresses prevalent in cold-arid or semi-arid climates worldwide. We hypothesized that the reproduction of the acclimated plants will be compromised and affected. Arabidopsis plants were submitted to long-term combined stress from the beginning to the reproductive stage, when floral bud was visible, until the silique development. Our results demonstrate severe morpho-anatomical changes after acclimation to combined stress. Inflorescence stem morphology was altered having a delayed bolting and a limited growth. Flowering and silique formation were delayed, and a higher size in the corolla and the petals was observed. Flower and silique number were severely diminished as a result of combined stress, unlike acclimated plants to individual cold stress. These traits were recovered after deacclimation to optimal conditions and plants achieved similar silique production as control plants. The long-term stress results suggest that there is not a single dominant stress, but there is an alternating dominance depending on the structure or the plant stage development evaluated.

Molecular tool for monitoring the safety of Aedes (Stegomyia) aegypti Rockefeller rearing in arthropod containment facilities

Abstract The interest in and use of Aedes (Stegomyia) aegypti (Linnaeus) (Diptera: Culicidae) insectary lines increased in most laboratories around the world since the recognition of the transmission of human and animal pathogens by this mosquito species, resulting in further scientific research on tropical diseases and vectors, and the development of chemical and biological products for mosquito populations control. In recent years, approaches to mosquito populations reduction have focused on new technologies that include the release of Wolbachia-infected lines, genetically modified vector and insects subjected to radiation in the Sterile Insect Technique. In order to evaluate some of these techniques, it is essential to count with wild A. aegypti populations and the reference strain, accurately identified, maintained under laboratory conditions. This work proposes a new tool to monitor possible exchanges between reference mosquito strain and wild native populations of A. aegypti in neighboring areas, or between different lines in the same insectary. We aligned and compared ND5 gene fragments of A. aegypti from diverse sources, finding a region with putative Single Nucleotide Polymorphisms between individuals of Rockefeller (Rock) strain and different wild A. aegypti populations. These polymorphic sites in the molecular marker, allowed us to discriminate Rock reference strain from the wild A. aegypti haplotypes found in the southeast of Argentina and bordering areas with Brazil, Uruguay and Paraguay, and it can be useful as a tool for regulatory entities of mosquito insectaries at different Arthropod Containment Levels.

The riddle of mitochondrial alkaline/neutral invertases: A novel Arabidopsis isoform mainly present in reproductive tissues and involved in root ROS production.

Alkaline/neutral invertases (A/N-Inv), glucosidases that irreversibly hydrolyze sucrose into glucose and fructose, play significant roles in plant growth, development, and stress adaptation. They occur as multiple isoforms located in the cytosol or organelles. In Arabidopsis thaliana, two mitochondrial A/N-Inv genes (A/N-InvA and A/N-InvC) have already been investigated. In this study, we functionally characterized A/N-InvH, a third Arabidopsis gene coding for a mitochondrial-targeted protein. The phenotypic analysis of knockout mutant plants (invh) showed a severely reduced shoot growth, while root development was not affected. The emergence of the first floral bud and the opening of the first flower were the most affected stages, presenting a significant delay. A/N-InvH transcription is markedly active in reproductive tissues. It is also expressed in the elongation and apical meristem root zones. Our results show that A/N-InvH expression is not evident in photosynthetic tissues, despite being of relevance in developmental processes and mitochondrial functional status. NaCl and mannitol treatments increased A/N-InvH expression twofold in the columella root cap. Moreover, the absence of A/N-InvH prevented ROS formation, not only in invh roots of salt- and ABA-treated seedlings but also in invh control roots. We hypothesize that this isoform may take part in the ROS/sugar (sucrose or its hydrolysis products) signaling pathway network, involved in reproductive tissue development, cell elongation, and abiotic stress responses.