Shaping the Organ: A Biologist Guide to Quantitative Models of Plant Morphogenesis

Organ morphogenesis is the process of shape acquisition initiated with a small reservoir of undifferentiated cells. In plants, morphogenesis is a complex endeavor that comprises a large number of interacting elements, including mechanical stimuli, biochemical signaling, and genetic prerequisites. Because of the large body of data being produced by modern laboratories, solving this complexity requires the application of computational techniques and analyses. In the last two decades, computational models combined with wet-lab experiments have advanced our understanding of plant organ morphogenesis. Here, we provide a comprehensive review of the most important achievements in the field of computational plant morphodynamics. We present a brief history from the earliest attempts to describe plant forms using algorithmic pattern generation to the evolution of quantitative cell-based models fueled by increasing computational power. We then provide an overview of the most common types of “digital plant” paradigms, and demonstrate how models benefit from diverse techniques used to describe cell growth mechanics. Finally, we highlight the development of computational frameworks designed to resolve organ shape complexity through integration of mechanical, biochemical, and genetic cues into a quantitative standardized and user-friendly environment.

A Small and High-Speed Driving Mechanism for 3D Shape Measurement in Monocular Endoscopy

Three-dimensional (3D) shape acquisition has been widely introduced to enrich quantitative analysis with the combination of object shape and texture, for example, surface roughness evaluation in industry and gastrointestinal endoscopy in medicine. Shape from focus is a promising technique to measure substance surfaces in 3D space because no occlusion problem appears in principle, as does with stereo shape measurement, which is another commonly used option. We have been developing endoscopic shape measurement devices and shape reconstruction algorithms. In this paper, we propose a mechanism for driving an image sensor reciprocated for the shape from focus of 3D shape measurement in monocular endoscopy. It uses a stepping motor and a planar-end cam, which transforms the motor rotation to imaging sensor reciprocation, to implement the shape from focus of 3D shape measurement in endoscopy. We test and discuss the device in terms of its driving accuracy and application feasibility for endoscopic 3D shape measurement.

Fluctuating auxin response gradients determine pavement cell-shape acquisition

Puzzle-shaped pavement cells provide a powerful model system to investigate the cellular and subcellular processes underlying complex cell-shape determination in plants. To better understand pavement cell-shape acquisition and the role of auxin in this process, we focused on the spirals of young stomatal lineage ground cells ofArabidopsisleaf epidermis. The predictability of lobe formation in these cells allowed us to demonstrate that the auxin response gradient forms within the cells of the spiral and fluctuates based on the particular stage of lobe development. We revealed that specific localization of auxin transporters at the different membranes of these young cells changes during the course of lobe formation, suggesting that these fluctuating auxin response gradients are orchestrated via auxin transport to control lobe formation and determine pavement cell shape.

Wireless Photoplethysmography Sensor for Continuous Blood Pressure Biosignal Shape Acquisition

Blood pressure assessment plays a vital role in day-to-day clinical diagnosis procedures as well as personal monitoring. Thus, blood pressure monitoring devices must afford convenience and be easy to use with no side effects on the user. This paper presents a compact, economical, power-efficient, and convenient wireless plethysmography sensor for real-time blood pressure biosignal monitoring. The proposed sensor facilitates blood pressure signal shape sensing, signal conditioning, and data conversion as well as its wireless transmission to a monitoring terminal. Received data can, subsequently, be compiled and stored on a computer via a Wi-Fi module. During monitoring, users can observe blood pressure signals being processed and displayed on the graphical user interface (GUI)—developed using a virtual instrumentation (VI) application. The proposed device comprises a finger clip optical pulse sensor, analogue signal preprocessing, microcontroller, and Wi-Fi module. It consumes approximately 500 mW power when operating in the active mode and synthesized using commercial off-the-shelf (COTS) components. Experimental results reveal that the proposed device is reliable and facilitates efficient blood pressure monitoring. The proposed wireless photoplethysmographic (PPG) sensor is a preliminary (or first) version of the intended device manifestation. It provides raw blood pressure data for further classification. Additionally, the collected data concerning the blood pressure wave shape can be easily analysed for use in other biosignal observations, interpretations, and investigations. The design approach also allows the device to be built into a wearable system for further research purposes.

Attitudes and exposure as predictors of -t/d deletion among local and expatriate children in Singapore

Although orientation towards local norms is increasing in Singapore, Singapore English (SgE) is still perceived by some as a nonnative variety. Variation in attitudes towards SgE may shape acquisition of SgE features by both Singaporean and expatriate children, who increasingly attend government schools. The present study investigates how the -t/d deletion patterns of 60 children reflect their attitudes and school setting. Significant correlations are observed between deletion rate, attitude towards SgE, and accent self-perception among Singaporean children, highlighting that this variety is undergoing endonormative stabilization. However, while some expatriates in local schools delete more than peers in international schools, expatriate children generally do not acquire local -t/d deletion rates or constraints, regardless of familiarity with SgE or attitudes towards the variety. This gap between locals and expatriates reflects the persistence of ideologies that delegitimize SgE, as well as the growing prominence of SgE as a marker of local identity.

The Hippo pathway effector Taz is required for cell fate specification and fertilization in zebrafish

SUMMARYIn the last decade, Hippo signaling has emerged as a critical pathway integrating extrinsic and intrinsic mechanical cues to regulate cell proliferation and survival, tissue morphology and organ size in vivo. Despite its essential role in organogenesis, surprisingly much less is known about how it connects biomechanical signals to control of cell fate and cell size during development. Here we unravel a novel and unexpected role of the Hippo pathway effector Taz (wwtr1) in the control of cell size and cell fate specification. In teleosts, fertilization occurs through a specific structure at the animal pole, called the micropyle. This opening in the chorion is formed during oogenesis by a specialized somatic follicle cell, the micropylar cell (MC). The MC has a peculiar shape and is much larger than its neighboring follicle cells but the mechanisms underlying its specification and cell shape acquisition are not known. Here we show that Taz is essential for the specification of the MC and subsequent micropyle formation in zebrafish. We identify Taz as the first bona fide MC marker and show that Taz is specifically and strongly enriched in the MC precursor before the cell can be identified morphologically. Altogether, our genetic data and molecular characterization of the MC lead us to propose that Taz is a key regulator of the MC fate activated by physical cues emanating from the oocyte to initiate the MC morphogenetic program. We describe here for the first time the mechanism underlying the specification of the MC fate.