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Quiescent centre (QC) cells represent an integral part of the root stem cell niche. They typically display a low division frequency that has been reported to be controlled by hormone signaling and different regulators, including the ETHYLENE RESPONSE FACTOR 115 (ERF115) transcription factor and D-type cyclins. Here, we applied a three-dimensional (3D) imaging to visualize the Arabidopsis QC cell number, volume and division patterns, including visualization of anticlinal divisions that cannot be deduced from longitudinal 2D imaging. We found that 5-day-old seedlings possess on average eight QC cells which are organized in a monolayered disc. In a period of 7 d, half of the QC cells undergo anticlinal division in a largely invariant space. Ectopic expression of ERF115 and CYCLIN D1;1 (CYCD1;1) promote both anticlinal and periclinal QC cell divisions, the latter resulting in a dual-layered QC zone holding up to 2-fold more QC cells compared with the wild type. In contrast, application of cytokinin or ethylene results in an increase in the number of periclinal, but a decrease in anticlinal QC divisions, suggesting that they control the orientation of QC cell division. Our data illustrate the power of 3D visualization in revealing unexpected QC characteristics. [ABSTRACT FROM AUTHOR]

Plant roots possess remarkable regenerative potential owing to their ability to replenish damaged or lost stem cells. ETHYLENE RESPONSE FACTOR 115 (ERF115), one of the key molecular elements linked to this potential, plays a predominant role in the activation of regenerative cell divisions. However, the downstream operating molecular machinery driving wound-activated cell division is largely unknown. Here, we biochemically and genetically identified the GRAS-domain transcription factor SCARECROW-LIKE 5 (SCL5) as an interaction partner of ERF115 in Arabidopsis thaliana. Although nonessential under control growth conditions, SCL5 acts redundantly with the related PHYTOCHROME A SIGNAL TRANSDUCTION 1 (PAT1) and SCL21 transcription factors to activate the expression of the DNA-BINDING ONE FINGER 3.4 (DOF3.4) transcription factor gene. DOF3.4 expression is wound-inducible in an ERF115-dependent manner and, in turn, activates D3-type cyclin expression. Accordingly, ectopic DOF3.4 expression drives periclinal cell division, while its downstream D3-type cyclins are essential for the regeneration of a damaged root. Our data highlight the importance and redundant roles of the SCL5, SCL21, and PAT1 transcription factors in wound-activated regeneration processes and pinpoint DOF3.4 as a key downstream element driving regenerative cell division. [ABSTRACT FROM AUTHOR]

Somatic polyploidy caused by endoreplication is observed in arthropods, molluscs, and vertebrates but is especially prominent in higher plants, where it has been postulated to be essential for cell growth and fate maintenance. However, a comprehensive understanding of the physiological significance of plant endopolyploidy has remained elusive. Here, we modeled and experimentally verified a high-resolution DNA endoploidy map of the developing Arabidopsis thaliana root, revealing a remarkable spatiotemporal control of DNA endoploidy levels across tissues. Fitting of a simplified model to publicly available data sets profiling root gene expression under various environmental stress conditions suggested that this root endoploidy patterning may be stress-responsive. Furthermore, cellular and transcriptomic analyses revealed that inhibition of endoreplication onset alters the nuclear-to-cellular volume ratio and the expression of cell wall-modifying genes, in correlation with the appearance of cell structural changes. Our data indicate that endopolyploidy might serve to coordinate cell expansion with structural stability and that spatiotemporal endoreplication pattern changes may buffer for stress conditions, which may explain the widespread occurrence of the endocycle in plant species growing in extreme or variable environments. [ABSTRACT FROM AUTHOR]

Objectives: The objectives of this study were to determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization in livestock and related workers in four Chinese provinces and the characteristics of these isolates. [ABSTRACT FROM PUBLISHER]