Company matters: The presence of other genotypes alters traits and intraspecific selection in an Arctic diatom under climate change

Arctic phytoplankton and their response to future conditions shape one of the most rapidly changing ecosystems on the planet. We tested how much the phenotypic responses of strains from the same Arctic diatom population diverge and whether the physiology and intraspecific composition of multistrain populations differs from expectations based on single strain traits. To this end, we conducted incubation experiments with the diatom Thalassiosira hyalina under present‐day and future temperature and pCO₂ treatments. Six fresh isolates from the same Svalbard population were incubated as mono‐ and multistrain cultures. For the first time, we were able to closely follow intraspecific selection within an artificial population using microsatellites and allele‐specific quantitative PCR. Our results showed not only that there is substantial variation in how strains of the same species cope with the tested environments but also that changes in genotype composition, production rates, and cellular quotas in the multistrain cultures are not predictable from monoculture performance. Nevertheless, the physiological responses as well as strain composition of the artificial populations were highly reproducible within each environment. Interestingly, we only detected significant strain sorting in those populations exposed to the future treatment. This study illustrates that the genetic composition of populations can change on very short timescales through selection from the intraspecific standing stock, indicating the potential for rapid population level adaptation to climate change. We further show that individuals adjust their phenotype not only in response to their physicochemical but also to their biological surroundings. Such intraspecific interactions need to be understood in order to realistically predict ecosystem responses to global change.     

Synergistic effect of extracellularly supplemented osteopontin and osteocalcin on stem cell proliferation,osteogenic differentiation,and angiogenic properties

A high demand for functional bone grafts is being observed worldwide, especially due to the increased life expectancy. Osteoinductive components should be incorporated into functional bone grafts, accelerating cell recruitment, cell proliferation, angiogenesis, and new bone formation at a defect site. Noncollagenous bone matrix proteins, especially osteopontin (OPN) and osteocalcin (OC), have been reported to regulate some physiological process, such as cell migration and bone mineralization. However, the effects of OPN and OC on cell proliferation, osteogenic differentiation, mineralization, and angiogenesis are still undefined. Therefore, we assessed the exogenous effect of OPN and OC supplementation on human bone marrow mesenchymal stem/stromal cells (hBM MSC) proliferation and osteogenic differentiation. OPN dose-dependently increased the proliferation of hBM MSC, as well as improved the angiogenic properties of human umbilical vein endothelial cells (HUVEC) by increasing the capillary-like tube formation in vitro. On the other hand, OC enhanced the differentiation of hBM MSC into osteoblasts and demonstrated an increase in extracellular calcium levels and alkaline phosphatase activity, as well as higher messenger RNA levels of mature osteogenic markers osteopontin and osteocalcin. In vivo assessment of OC/OPN-enhanced scaffolds in a critical-sized defect rabbit long-bone model revealed no infection, while new bone was being formed. Taken together, these results suggest that OC and OPN stimulate bone regeneration by inducing stem cell proliferation, osteogenesis and by enhancing angiogenic properties. The synergistic effect of OC and OPN observed in this study can be applied as an attractive strategy for bone regeneration therapeutics by targeting different vital cellular processes.     

Enzyme function less conserved than anticipated

The level of sequence similarity that implies similarity in protein structure is well established. Recently, many groups proposed thresholds for similarity in sequence implying similarity in enzymatic function. All previous results suggest the strong conservation of enzymatic function above levels of 50% pairwise sequence identity. Here, I argue that all groups substantially overestimated the conservation of enzyme function because their data sets were either too biased, or too small. An unbiased analysis suggested that less than 30% of the pair fragments above 50% sequence identity have entirely identical EC numbers. Another surprising finding was that even BLAST E-values below 10(-50) did not suffice to automatically transfer enzyme function without errors. As expected, most misclassifications originated from similarities in relatively short regions and/or from transferring annotations for different domains. Both problems cannot be corrected easily by adjusting the thresholds for automatic transfer of genome annotations. A score relating sequence identity to alignment length (distance from HSSP-threshold) outperformed statistical BLAST scores for high sequence similarity. In particular, the distance score allowed error-free transfer of enzyme function for the 10% most similar enzyme pairs. The results illustrated how difficult it is to assess the conservation of protein function and to guarantee error-free genome annotations, in general: sets with millions of pair comparisons might not suffice to arrive at statistically significant conclusions. In practice, the revised detailed estimates for the sequence conservation of enzyme function may provide important benchmarks for everyday sequence analysis and for more cautious automatic genome annotations.     

Protein disorder--a breakthrough invention of evolution?

As an operational definition, we refer to regions in proteins that do not adopt regular three-dimensional structures in isolation, as disordered regions. An antipode to disorder would be 'well-structured' rather than 'ordered'. Here, we argue for the following three hypotheses. Firstly, it is more useful to picture disorder as a distinct phenomenon in structural biology than as an extreme example of protein flexibility. Secondly, there are many very different flavors of protein disorder, nevertheless, it seems advantageous to portray the universe of all possible proteins in terms of two main types: well-structured, disordered. There might be a third type 'other' but we have so far no positive evidence for this. Thirdly, nature uses protein disorder as a tool to adapt to different environments. Protein disorder is evolutionarily conserved and this maintenance of disorder is highly nontrivial. Increasingly integrating protein disorder into the toolbox of a living cell was a crucial step in the evolution from simple bacteria to complex eukaryotes. We need new advanced computational methods to study this new milestone in the advance of protein biology.     

Augmentation of partially regenerated nerves by end-to-side side-to-side grafting neurotization: experience based on eight late obstetric brachial plexus cases

Objective

The effect of end-to-side neurotization of partially regenerated recipient nerves on improving motor power in late obstetric brachial plexus lesions, so-called nerve augmentation, was investigated.

Methods

Eight cases aged 3 – 7 years were operated upon and followed up for 4 years (C5,6 rupture C7,8T1 avulsion: 5; C5,6,7,8 rupture T1 avulsion:1; C5,6,8T1 rupture C7 avulsion:1; C5,6,7 ruptureC8 T1 compression: one 3 year presentation after former neurotization at 3 months). Grade 1–3 muscles were neurotized. Grade0 muscles were neurotized, if the electromyogram showed scattered motor unit action potentials on voluntary contraction without interference pattern. Donor nerves included: the phrenic, accessory, descending and ascending loops of the ansa cervicalis, 3^rd and 4^th intercostals and contralateral C7.

Results

Superior proximal to distal regeneration was observed firstly. Differential regeneration of muscles supplied by the same nerve was observed secondly (superior supraspinatus to infraspinatus regeneration). Differential regeneration of antagonistic muscles was observed thirdly (superior biceps to triceps and pronator teres to supinator recovery). Differential regeneration of fibres within the same muscle was observed fourthly (superior anterior and middle to posterior deltoid regeneration). Differential regeneration of muscles having different preoperative motor powers was noted fifthly; improvement to Grade 3 or more occurred more in Grade2 than in Grade0 or Grade1 muscles. Improvements of cocontractions and of shoulder, forearm and wrist deformities were noted sixthly. The shoulder, elbow and hand scores improved in 4 cases.

Limitations

The sample size is small. Controls are necessary to rule out any natural improvement of the lesion. There is intra- and interobserver variability in testing muscle power and cocontractions.

Conclusion

Nerve augmentation improves cocontractions and muscle power in the biceps, pectoral muscles, supraspinatus, anterior and lateral deltoids, triceps and in Grade2 or more forearm muscles. As it is less expected to improve infraspinatus power, it should be associated with a humeral derotation osteotomy and tendon transfer. Function to non improving Grade 0 or 1 forearm muscles should be restored by muscle transplantation.

Level of evidence

Level IV, prospective case series.     

Pericycle cell proliferation and lateral root initiation in Arabidopsis

In contrast with other cells generated by the root apical meristem in Arabidopsis, pericycle cells adjacent to the protoxylem poles of the vascular cylinder continue to cycle without interruption during passage through the elongation and differentiation zones. However, only some of the dividing pericycle cells are committed to the asymmetric, formative divisions that give rise to lateral root primordia (LRPs). This was demonstrated by direct observation and mapping of mitotic figures, cell-length measurements, and the histochemical analysis of a cyclin-GUS fusion protein in pericycle cells. The estimated duration of a pericycle cell cycle in the root apical meristem was similar to the interval between cell displacement from the meristem and the initiation of LRP formation. Developmentally controlled LRP initiation occurs early, 3 to 8 mm from the root tip. Thus the first growth control point in lateral root formation is defined by the initiation of primordia in stochastic patterns by cells passing through the elongation and young differentiation zones, up to where lateral roots begin to emerge from the primary root. Therefore, the first growth control point is not restricted to a narrow developmental window. We propose that late LRP initiation is developmentally unrelated to the root apical meristem and is operated by a second growth control point that can be activated by environmental cues. The observation that pericycle cells divide and lateral root primordia form without intervening mitotic quiescence suggests that lateral organ formation in roots and shoots might not be as fundamentally different as previously thought.     

MITOTIC ACTIVITY IN THE ROOT APICAL MERISTEM OF AZOLLA FILICULOIDES LAM., WITH SPECIAL REFERENCE TO THE APICAL CELL

The meristematic activity of the apical cell and its derivatives (merophytes) in the unbranched, determinate roots of Azolla filiculoides Lam. was investigated. The plane of division of the apical cell indicates that it is the initial of each merophyte. The division plane of each newly formed merophyte is strictly periclinal to the root surface and provides confirmation that the immediate derivatives of the apical cell cannot be the ultimate root initials. The frequency of cell division as determined by the mitotic index, and by the duration of the cell cycle as determined by the colchicine method, confirmed the meristematic activity of the apical cell. As roots increase in length, the duration of the cell cycle in the total meristem increases, with the apical cell possessing the longest cell cycle, whereas the immediate derivatives maintain approximately the same cycle duration as in shorter roots. In determinate Azolla roots, cell division appears to play a major role up to a certain root length, then increase in length is produced mainly by cell elongation.     

Expression and localization of the multidrug resistance-associated protein 3 in rat small and large intestine

Multidrug resistance-associated protein 3 (MRP3; symbol ABCC3), has been shown to mediate ATP-dependent transport of organic anions including 17beta-glucuronosyl estradiol, glucuronosyl bilirubin, monovalent, and sulfated bile salts. MRP3 mRNA expression was reported in rat intestine suggesting a role of MRP3 in the intestinal transport. We examined the expression and localization of MRP3 in rat small and large intestine by RT-PCR, immunofluorescence, and immunoblot analysis. MRP3 was identified in all intestinal segments by RT-PCR. MRP3 expression was low in duodenum and jejunum but markedly increased in ileum and colon. With the use of a rat MRP3 specific antibody, MRP3 was localized to the basolateral domains of enterocytes. Immunofluorescence analysis and immunoblot analysis confirmed a strong expression of rat MRP3 in ileum and colon. In contrast, MRP2 was predominantly expressed in the proximal segments of rat small intestine. Our findings demonstrate a high expression of rat MRP3 in ileum and colon and provide evidence for an involvement of MRP3 in the ATP-dependent transport of organic anions, including bile salts from the enterocyte into blood.     

Potential role of viruses in white plague coral disease

White plague (WP)-like diseases of tropical corals are implicated in reef decline worldwide, although their etiological cause is generally unknown. Studies thus far have focused on bacterial or eukaryotic pathogens as the source of these diseases; no studies have examined the role of viruses. Using a combination of transmission electron microscopy (TEM) and 454 pyrosequencing, we compared 24 viral metagenomes generated from Montastraea annularis corals showing signs of WP-like disease and/or bleaching, control conspecific corals, and adjacent seawater. TEM was used for visual inspection of diseased coral tissue. No bacteria were visually identified within diseased coral tissues, but viral particles and sequence similarities to eukaryotic circular Rep-encoding single-stranded DNA viruses and their associated satellites (SCSDVs) were abundant in WP diseased tissues. In contrast, sequence similarities to SCSDVs were not found in any healthy coral tissues, suggesting SCSDVs might have a role in WP disease. Furthermore, Herpesviridae gene signatures dominated healthy tissues, corroborating reports that herpes-like viruses infect all corals. Nucleocytoplasmic large DNA virus (NCLDV) sequences, similar to those recently identified in cultures of Symbiodinium (the algal symbionts of corals), were most common in bleached corals. This finding further implicates that these NCLDV viruses may have a role in bleaching, as suggested in previous studies. This study determined that a specific group of viruses is associated with diseased Caribbean corals and highlights the potential for viral disease in regional coral reef decline.