Recent Lateral Expansion of Sphagnum Bogs Over Central Fen Areas of Boreal Aapa Mire Complexes

We investigated recent changes in spatial patterning of fen and bog zones in five boreal aapa mire complexes (mixed peatlands with patterned fen and bog parts) in a multiproxy study. Comparison of old (1940–1970s) and new aerial images revealed decrease of flarks (wet hollows) in patterned fens by 33–63% in middle boreal and 16–42% in northern boreal sites, as lawns of bog Sphagnum mosses expanded over fens. Peat core transects across transformed areas were used to verify the remote sensing inference with stratigraphic analyses of macrofossils, hyperspectral imaging, and age-depth profiles derived from 14C AMS dating and pine pollen density. The transect data revealed that the changes observed by remote sensing during past decades originated already from the end of the Little Ice Age (LIA) between 1700–1850 CE in bog zones and later in the flarks of fen zones. The average lateral expansion rate of bogs over fen zones was 0.77 m y−1 (range 0.19–1.66) as estimated by remote sensing, and 0.71 m y−1 (range 0.13–1.76) based on peat transects. The contemporary plant communities conformed to the macrofossil communities, and distinct vegetation zones were recognized as representing recently changed areas. The fen-bog transition increased the apparent carbon accumulation, but it can potentially threaten fen species and habitats. These observations indicate that rapid lateral bog expansion over aapa mires may be in progress, but more research is needed to reveal if ongoing fen-bog transitions are a commonplace phenomenon in northern mires.

3D bioprinting for meniscus tissue engineering: a review of key components, recent developments and future opportunities

3D bioprinting has the potential to transform the field of regenerative medicine as it enables the precise spatial patterning of biomaterials, cells and biomolecules to produce engineered tissues. Although numerous tissue engineering strategies have been developed for meniscal repair, the field has yet to realize an implant capable of completely regenerating the tissue. This paper first summarized existing meniscal repair strategies, highlighting the importance of engineering biomimetic implants for successful meniscal regeneration. Next, we reviewed how developments in 3D (bio)printing are accelerating the engineering of functional meniscal tissues and the development of implants targeting damaged or diseased menisci. Some of the opportunities and challenges associated with use of 3D bioprinting for meniscal tissue engineering are identified. Finally, we discussed key emerging research areas with the capacity to enhance the bioprinting of meniscal grafts.

A shared transcriptional code orchestrates temporal patterning of the central nervous system

The molecular mechanisms that produce the full array of neuronal subtypes in the vertebrate nervous system are incompletely understood. Here, we provide evidence of a global temporal patterning program comprising sets of transcription factors that stratifies neurons based on the developmental time at which they are generated. This transcriptional code acts throughout the central nervous system, in parallel to spatial patterning, thereby increasing the diversity of neurons generated along the neuraxis. We further demonstrate that this temporal program operates in stem cell−derived neurons and is under the control of the TGFβ signaling pathway. Targeted perturbation of components of the temporal program, Nfia and Nfib, reveals their functional requirement for the generation of late-born neuronal subtypes. Together, our results provide evidence for the existence of a previously unappreciated global temporal transcriptional program of neuronal subtype identity and suggest that the integration of spatial and temporal patterning mechanisms diversifies and organizes neuronal subtypes in the vertebrate nervous system.

Patterning with clocks and genetic cascades: Segmentation and regionalization of vertebrate versus insect body plans

Oscillatory and sequential processes have been implicated in the spatial patterning of many embryonic tissues. For example, molecular clocks delimit segmental boundaries in vertebrates and insects and mediate lateral root formation in plants, whereas sequential gene activities are involved in the specification of regional identities of insect neuroblasts, vertebrate neural tube, vertebrate limb, and insect and vertebrate body axes. These processes take place in various tissues and organisms, and, hence, raise the question of what common themes and strategies they share. In this article, we review 2 processes that rely on the spatial regulation of periodic and sequential gene activities: segmentation and regionalization of the anterior–posterior (AP) axis of animal body plans. We study these processes in species that belong to 2 different phyla: vertebrates and insects. By contrasting 2 different processes (segmentation and regionalization) in species that belong to 2 distantly related phyla (arthropods and vertebrates), we elucidate the deep logic of patterning by oscillatory and sequential gene activities. Furthermore, in some of these organisms (e.g., the fruit fly Drosophila), a mode of AP patterning has evolved that seems not to overtly rely on oscillations or sequential gene activities, providing an opportunity to study the evolution of pattern formation mechanisms.

Bidirectional cell-cell communication via indole and cyclo(Pro-Tyr) modulates interspecies biofilm formation

The extracellular signaling molecule indole plays a pivotal role in biofilm formation by the enteric γ-Proteobacterium Escherichia coli ; this process is particularly correlated with extracellular indole concentration. Using indole-biodegrading β-Proteobacterium Burkholderia unamae , we examined the mechanism by which these two bacteria modulate biofilm formation in an indole-dependent manner. We quantified the spatial organization of cocultured microbial communities at the micron-scale through computational image analysis, ultimately identifying how bidirectional cell-to-cell communication modulated the physical relationships between them. Further analysis allowed us to determine the mechanism by which the B. unamae -derived signaling diketopiperazine, cyclo(Pro-Tyr), considerably upregulated indole biosynthesis and enhanced E. coli biofilm formation. We also determined that the presence of unmetabolized indole enhanced production of cyclo(Pro-Tyr). Thus, bidirectional cell-to-cell communication that occurred via interspecies signaling molecules modulated formation of a mixed-species biofilm between indole-producing and indole-consuming species. Importance Indole is a relatively stable N -heterocyclic aromatic compound that is widely found in nature. To date, the correlations between indole-related bidirectional cell-to-cell communications and interspecies communal organization remain poorly understood. In this study, we used an experimental model, which consisted of indole-producing and indole-degrading bacteria, to evaluate how bidirectional cell-to-cell communication modulated interspecies biofilm formation via intrinsic and environmental cues. We identified a unique spatial patterning of indole-producing and indole-degrading bacteria within mixed-species biofilms. This spatial patterning was an active process mediated by bidirectional physico-chemical interactions. Our findings represent an important step in gaining a more thorough understanding of the process of polymicrobial biofilm formation and advance the possibility of using indole degrading bacteria to address biofilm-related health and industry issues.