WUSCHEL-RELATED HOMEOBOX 13 suppresses de novo shoot regeneration via cell fate control of pluripotent callus.

Plants can regenerate their bodies via de novo establishment of shoot apical meristems (SAMs) from pluripotent callus. Only a small fraction of callus cells is eventually specified into SAMs but the molecular mechanisms underlying fate specification remain obscure. The expression of WUSCHEL (WUS) is an early hallmark of SAM fate acquisition. Here, we show that a WUS paralog, WUSCHEL-RELATED HOMEOBOX 13 (WOX13), negatively regulates SAM formation from callus in Arabidopsis thaliana. WOX13 promotes non-meristematic cell fate via transcriptional repression of WUS and other SAM regulators and activation of cell wall modifiers. Our Quartz-Seq2-based single cell transcriptome revealed that WOX13 plays key roles in determining cellular identity of callus cell population. We propose that reciprocal inhibition between WUS and WOX13 mediates critical cell fate determination in pluripotent cell population, which has a major impact on regeneration efficiency.

Auxin-Induced WUSCHEL-RELATED HOMEOBOX13 Mediates Asymmetric Activity of Callus Formation upon Cutting.

Plants have the regenerative ability to reconnect cut organs, which is physiologically important to survive severe tissue damage. The ability to reconnect organs is utilized as grafting to combine two different individuals. Callus formation at the graft junction facilitates organ attachment and vascular reconnection. While it is well documented that local wounding signals provoke callus formation, how callus formation is differentially regulated at each cut end remains elusive. Here, we report that callus formation activity is asymmetrical between the top and bottom cut ends and is regulated by differential auxin accumulation. Gene expression analyses revealed that cellular auxin response is preferentially upregulated in the top part of the graft. Disruption of polar auxin transport inhibited callus formation from the top, while external application of auxin was sufficient to induce callus formation from the bottom, suggesting that asymmetric auxin accumulation is responsible for active callus formation from the top end. We further found that the expression of a key regulator of callus formation, WUSCHEL-RELATED HOMEOBOX 13 (WOX13), is induced by auxin. The ectopic callus formation from the bottom end, which is triggered by locally supplemented auxin, requires WOX13 function, demonstrating that WOX13 plays a pivotal role in auxin-dependent callus formation. The asymmetric WOX13 expression is observed both in grafted petioles and incised inflorescence stems, underscoring the generality of our findings. We propose that efficient organ reconnection is achieved by a combination of local wounding stimuli and disrupted long-distance signaling.

A risk assessment framework for self-management of poorly soluble low toxic nanomaterials.

The safety of nanomaterials is still being debated and the risk should be assessed using the latest available information. As for poorly soluble low toxic (PSLT) nanomaterials, the US National Institute for Occupational Safety and Health estimated the occupational exposure limit (OEL) for titanium dioxide (TiO2) based on a particle surface area (SA) metric. The Organisation for Economic Co-operation and Development (OECD) suggested a tiered exposure assessment approach. This article proposes a risk assessment framework for self-management of PSLT particles. Lung burden (described in SA units), which had positive correlation with low observed adverse effect levels for PSLT particles, is chosen as the dose metric. In-house OEL is determined for individual workplaces. For materials with limited data, we suggest evaluating in-house OEL by utilizing the no observed adverse effect level (NOAEL) for TiO2, as a representative PSLT nanomaterial. As for the exposure assessment, workplace concentration is first measured with simple equipment (ex. optical particle counter, OPC), and respirator performance is taken into account if it is unavoidable as a last resort. This framework enables efficient risk assessment for PSLT particles by assuming worst cases for each step, and considering the particle characteristics and operational conditions in each workplace.

Plasma cytokine profiles in subjects with high-functioning autism spectrum disorders.

BACKGROUND: Accumulating evidence suggests that dysregulation of the immune system is involved in the pathophysiology of autism spectrum disorders (ASD). The aim of the study was to explore immunological markers in peripheral plasma samples from non-medicated subjects with high-functioning ASD. METHODOLOGY/PRINCIPAL FINDINGS: A multiplex assay for cytokines and chemokines was applied to plasma samples from male subjects with high-functioning ASD (n = 28) and matched controls (n = 28). Among a total of 48 analytes examined, the plasma concentrations of IL-1ß, IL-1RA, IL-5, IL-8, IL-12(p70), IL-13, IL-17 and GRO-α were significantly higher in subjects with ASD compared with the corresponding values of matched controls after correction for multiple comparisons. CONCLUSION/SIGNIFICANCE: The results suggest that abnormal immune responses as assessed by multiplex analysis of cytokines may serve as one of the biological trait markers for ASD.

Reduction in cerebral blood flow volume in infants complicated with hypoxic ischemic encephalopathy resulting in cerebral palsy.

Hypoxic ischemic brain can result in cerebral palsy, mental retardation, and learning disabilities in surviving children. The purpose of this study was to elucidate the cerebral blood flow volume in infants complicated with brain damage after the birth. Nine term infants with hypoxic ischemic encephalopathy and 41 normal term infants were studied. Four infants with HIE suffered from CP or mental retardation, and the other five infants exhibited normal neurodevelopment. The mean blood flow velocity and diameter of the internal carotid artery and the vertebral artery were measured for 28 days. The intravascular flow volume was determined by calculating the flow velocity and the cross-sectional area. The ejection fraction and cardiac output were obtained, and the mean blood pressures were recorded. The summed flow volumes in both the ICA and VA, and the total CBFV increased after the birth in both the normal infants and the infants diagnosed with HIE with no disability complications. The total blood flow volume was significantly lower in infants with HIE and CP than in normal infants on days 0, 2, 5, 7, 10, 21, and 28, and significantly lower in infants with HIE and CP than in normal infants with HIE on days 2, 4, and 7. The ejection fraction was significantly lower in infants with HIE than in normal infants only on day 0. Our results suggest that the total cerebral blood supply is decreased in infants with HIE in those complicated with brain damage.

Pseudomonas azotifigens sp. nov., a novel nitrogen-fixing bacterium isolated from a compost pile.

A nitrogen-fixing bacterium, designated strain 6H33b(T), was isolated from a compost pile in Japan. The nitrogenase activity of this strain was detected based on its acetylene-reducing activity under low oxygen concentrations (2-4%). An analysis of the genes responsible for nitrogen fixation in this strain, nifH and nifD, indicated a close relationship to those of Pseudomonas stutzeri A15 (A1501). Sequence similarity searches based on the 16S rRNA gene sequences showed that strain 6H33b(T) belongs within the genus Pseudomonas sensu stricto; closest similarity was with Pseudomonas indica (97.3%). A comparison of several taxonomic characteristics of 6H33b(T) with those of P. indica and some type strains of the genus Pseudomonas sensu stricto indicated that 6H33b(T) could be distinguished from P. indica based on the presence of nitrogen fixation ability, the absence of nitrate reduction and denitrification abilities and the utilization of some sugars and organic acids. Phylogenetic analyses and the results of DNA-DNA hybridization experiments also indicated that strain 6H33b(T) represents a species distinct from P. indica. From these results, it is proposed that strain 6H33b(T) (=ATCC BAA-1049(T)=JCM 12708(T)) is classified as the type strain of a novel species of the genus Pseudomonas sensu stricto under the name Pseudomonas azotifigens sp. nov.