Growth and physiological responses of subalpine forbs to nitrogen and soil moisture: investigating the potential roles of plant functional traits

Anthropogenic inputs of biologically available nitrogen (N) and climate change are simultaneously altering N and soil moisture availability in terrestrial ecosystems. Yet, plant responses to concurrent changes in both N and soil moisture in non-grassland ecosystems remain poorly understood. Our objective was to investigate how rooting depth and N-fixing ability—two functional traits we expected to mediate soil moisture and N limitations—influence forb responses to N and soil moisture availability in the Rocky Mountains USA. We assessed the growth and physiological responses (i.e., chlorophyll fluorescence, transpiration rate, and floral display) of four subalpine forb species to N additions across a naturally-occurring soil moisture gradient during one growing season. Soil moisture had a stronger positive effect on growth in shallow-rooted species and N additions had a stronger positive effect on photosynthetic capacity in species without N-fixing abilities. Transpiration rates were not consistent with soil moisture limitations expected for shallow-rooted species, and soil moisture and N had a neutral or negative influence on maximum floral displays across species. Nitrogen and soil moisture appeared to each limit separate response variables in some cases and we did not observe any N?×?soil moisture interactions. These findings suggest that shallow-rooted species may be more vulnerable to increased drought severity and that increased N availability may disproportionately benefit species without N-fixing abilities. However, mixed support for our hypotheses suggests that environmental conditions and functional traits not evaluated here likely influence subalpine plant responses to soil moisture and N availability.     

Gliotoxin penetrates and impairs the integrity of the human blood-brain barrier in vitro

Cerebral fungal infections represent an important public health concern, where a key element of pathophysiology is the ability of the fungi to cross the blood-brain barrier (BBB). Yet the mechanism used by micro-organisms to cross such a barrier and invade the brain parenchyma remains unclear. This study investigated the effects of gliotoxin (GTX), a mycotoxin secreted by Aspergillus fumigatus, on the BBB using brain microvascular endothelial cells (BMECs) derived from induced pluripotent stem cells (iPSCs). We observed that both acute (2 h) and prolonged (24 h) exposure to GTX at the level of 1 μM or higher compromised BMECs monolayer integrity. Notably, acute exposure was sufficient to disrupt the barrier function in iPSC-derived BMECs, resulting in decreased transendothelial electrical resistance (TEER) and increased fluorescein permeability. Further, our data suggest that such disruption occurred without affecting tight junction complexes, via alteration of cell-matrix interactions, alterations in F-actin distribution, through a protein kinase C-independent signaling. In addition to its effect on the barrier function, we have observed a low permeability of GTX across the BBB. This fact can be partially explained by possible interactions of GTX with membrane proteins. Taken together, this study suggests that GTX may contribute in cerebral invasion processes of Aspergillus fumigatus by altering the blood-brain barrier integrity without disrupting tight junction complexes.     

Demographic expansion and genetic load of the halophyte model plant Eutrema salsugineum

The halophyte model plant Eutrema salsugineum (Brassicaceae) disjunctly occurs in temperate to subarctic Asia and North America. This vast, yet extremely discontinuous distribution constitutes an ideal system to examine long‐distance dispersal and the ensuing accumulation of deleterious mutations as expected in expanding populations of selfing plants. In this study, we resequenced individuals from 23 populations across the range of E. salsugineum. Our population genomic data indicate that E. salsugineum migrated “out of the Altai region” at least three times to colonize northern China, northeast Russia and western China. It then expanded its distribution into North America independently from northeast Russia and northern China, respectively. The species colonized northern China around 33.7 thousand years ago (kya) and underwent a considerable expansion in range size approximately 7–8 kya. The western China lineage is likely a hybrid derivative of the northern China and Altai lineages, originating approximately 25–30 kya. Deleterious alleles accumulated in a stepwise manner from (a) Altai to northern China and North America and (b) Altai to northeast Russia and North America. In summary, E. salsugineum dispersed from Asia to North America and deleterious mutations accumulated in a stepwise manner during the expansion of the species’ distribution.     

Trans‐species synthetic gene design allows resistance pyramiding and broad‐spectrum engineering of virus resistance in plants

To infect plants, viruses rely heavily on their host's machinery. Plant genetic resistances based on host factor modifications can be found among existing natural variability and are widely used for some but not all crops. While biotechnology can supply for the lack of natural resistance alleles, new strategies need to be developed to increase resistance spectra and durability without impairing plant development. Here, we assess how the targeted allele modification of the Arabidopsis thaliana translation initiation factor eIF4E1 can lead to broad and efficient resistance to the major group of potyviruses. A synthetic Arabidopsis thaliana eIF4E1 allele was designed by introducing multiple amino acid changes associated with resistance to potyvirus in naturally occurring Pisum sativum alleles. This new allele encodes a functional protein while maintaining plant resistance to a potyvirus isolate that usually hijacks eIF4E1. Due to its biological functionality, this synthetic allele allows, at no developmental cost, the pyramiding of resistances to potyviruses that selectively use the two major translation initiation factors, eIF4E1 or its isoform eIFiso4E. Moreover, this combination extends the resistance spectrum to potyvirus isolates for which no efficient resistance has so far been found, including resistance‐breaking isolates and an unrelated virus belonging to the Luteoviridae family. This study is a proof‐of‐concept for the efficiency of gene engineering combined with knowledge of natural variation to generate trans‐species virus resistance at no developmental cost to the plant. This has implications for breeding of crops with broad‐spectrum and high durability resistance using recent genome editing techniques.     

The beach‐spawning California grunion Leuresthes tenuis eats and digests conspecific eggs

Apparent egg cannibalism was investigated in the beach‐spawning California grunion Leuresthes tenuis. Three hypotheses were tested to determine whether L. tenuis regularly consumes and efficiently digests conspecific eggs. First, examination of the gut contents of adults collected at four spawning sites over two seasons showed that the intestines of most fish from all the sites (57–87%, n ≥ 30, each site) contained L. tenuis eggs. The two other hypotheses focused on digestion of the eggs. First, the force required to crush cannibalized eggs was significantly less than that for uncannibalized eggs (fertilized or unfertilized), indicating that ingestion weakens the egg chorions. Second, conspecific eggs fed to fish held in the laboratory visibly degraded as they passed through the gut. The eggs lost c. half of their protein content and about two‐thirds of their lipid content as they passed from proximal to distal regions of the gut, indicating that digestion occurred. Digestive enzyme activities of the gut further confirmed that L. tenuis can break down the contents of ingested eggs. Trypsin activity decreased and aminopeptidase activity increased posteriorly along the gut, whereas amylase and lipase activities exhibited less clear patterns by gut region. As far as is known, this study is the first to show that L. tenuis is an egg cannibal.     

A new species of Liolaemus related to L. nigroviridis from the Andean highlands of Central Chile (Iguania,Liolaemidae)

The Liolaemus nigroviridis group is a clade of highland lizards endemic to Chile. These species are distributed from northern to central Chile, and currently there are no cases of sympatric distribution. This study describes a new species, Liolaemus uniformis sp. n., from this group, and provides a detailed morphological characterization and mitochondrial phylogeny using cytochrome-b. Liolaemus uniformis was found in sympatry with Liolaemus nigroviridis but noticeably differed in size, scalation, and markedly in the color pattern, without sexual dichromatism. This new species has probably been confused with Liolaemus monticola and Liolaemus bellii, both of which do not belong to the nigroviridis group. The taxonomic issues of this group that remain uncertain are also discussed.     

Tool-set for termite-fishing and honey extraction by wild chimpanzees in the Lossi Forest, Congo

The use of perforating sticks and flexible stalks in combination for termite fishing and a complex tool-set of three components used sequentially (stout chiel, bodkin, and dip-stick) to penetrate melipone and ground-dwelling bee hives byPan troglodytes troglodytes are documented or, inferred from circumstantial evidence. Functionally, termite extraction tools were similar to other locations in west and central Africa, but the plants and the number of raw material species used were different. Tools varied in the degree of modification (fraying ends). Chimpanzees in the Lossi forest seem to be able to use the tools not in a stereotyped fashion, but in a flexible, insightful way. The extraction of Melipone honey using large pieces of wood as pounding tools has rarely been recorded elsewhere. The most impressive technological solution to the honey-getting problem by wild chimpanzees was shown by this study. This is the only known, use of a tool-set of three components in sequence to extract honey by wild chimpanzees.     

Microspore embryogenesis induced through in vitro anther culture of almond (<Emphasis Type="Italic">Prunus dulcis</Emphasis> Mill.)

Anther culture is one of the most widely used methods to induce gametic embryogenesis. The aim of this investigation was to induce microspore embryogenesis in almond (Prunus dulcis Mill.), through this technique. Anthers were cultured at the vacuolated developmental stage, and seven cultivars, two culture media and two temperature treatments were assessed. Although evidence of the microspore induction was observed in all the genotypes and treatments tested (symmetrical nucleus division and multinucleated structures), calli were produced merely by anthers cultured in the medium P and the regeneration of embryos was detected only in anthers of the cultivars Filippo Ceo, Lauranne and Genco, placed on medium P and subjected to the Control treatment (direct culture at 25?±?1?°C, without the hot thermal shock at 35?±?1?°C for 7 days). Characterization by SSR marker analysis of the embryo genotypes revealed that the regenerants had a single allele for each locus whereas the parent cultivar was heterozygous, indicating their development from haploid microspores. This study reports the evidence of gametic embryogenesis and, particularly, of microspore embryogenesis through in vitro anther culture, in almond, and, for the first time to our knowledge, the production of homozygous embryos.