In plants, the robust maintenance of tissue structure is crucial to supporting its functionality. The multi-layered shoot apical meristem (SAM) ofArabidopsis,containing stem cells,is an approximately radially symmetric tissue whose shape and structure is maintained throughout the life of the plant. In this paper, a new biologically calibrated pseudo-three-dimensional (P3D) computational model of a longitudinal section of the SAM is developed. It includes anisotropic expansion and division of cells out of the cross-section plane, as well as representation of tension experienced by the SAM epidermis. Results from the experimentally calibrated P3D model provide new insights into maintenance of the structure of the SAM epidermal cell monolayer under tension and quantify dependence of epidermal and subepidermal cell anisotropy on the amount of tension. Moreover, the model simulations revealed that out-of-plane cell growth is important in offsetting cell crowding and regulating mechanical stresses experienced by tunica cells. Predictive model simulations show that tension-determined cell division plane orientation in the apical corpus may be regulating cell and tissue shape distributions needed for maintaining structure of the wild-type SAM. This suggests that cells' responses to local mechanical cues may serve as a mechanism to regulate cell- and tissue-scale patterning.
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Deep Quantized Representation For Enhanced Reconstruction
While machine learning approaches have shown remarkable performance in biomedical image analysis, most of these methods rely on high-quality and accurate imaging data. However, collecting such data requires intensive and careful manual effort. One of the major challenges in imaging the Shoot Apical Meristem (SAM) of Arabidopsis thaliana, is that the deeper slices in the z-stack suffer from different perpetual quality related problems like poor contrast and blurring. These quality related issues often lead to disposal of the painstakingly collected data with little to no control on quality while collecting the data. Therefore, it becomes necessary to employ and design techniques that can enhance the images to make it more suitable for further analysis. In this paper, we propose a data-driven Deep Quantized Latent Representation (DQLR) methodology for high-quality image reconstruction in the Shoot Apical Meristem (SAM) of Arabidopsis thaliana. Our proposed framework utilizes multiple consecutive slices in the z-stack to learn a low dimensional latent space, quantize it and subsequently perform reconstruction using the quantized representation to obtain sharper images. Experiments on a publicly available dataset validate our methodology showing promising results. Our code is available at github.com/agupt013/enhancedRec.git.
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- PAR ID:
- 10245789
- Date Published:
- Journal Name:
- 2020 IEEE 17th International Symposium on Biomedical Imaging Workshops
- Page Range / eLocation ID:
- 1 to 4
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract In plants, the stem cells that form the shoot system reside within the shoot apical meristem (SAM), which is regulated by feedback signaling between the WUSCHEL (WUS) homeobox protein and CLAVATA (CLV) peptides and receptors. WUS–CLV feedback signaling can be modulated by various endogenous or exogenous factors, such as chromatin state, hormone signaling, reactive oxygen species (ROS) signaling and nutrition, leading to a dynamic control of SAM size corresponding to meristem activity. Despite these insights, however, the knowledge of genes that control SAM size is still limited, and in particular, the regulation by ROS signaling is only beginning to be comprehended. In this study, we report a new function in maintenance of SAM size, encoded by the OKINA KUKI1 (OKI1) gene. OKI1 is expressed in the SAM and encodes a mitochondrial aspartyl tRNA synthetase (AspRS). oki1 mutants display enlarged SAMs with abnormal expression of WUS and CLV3 and overaccumulation of ROS in the meristem. Our findings support the importance of normal AspRS function in the maintenance of the WUS–CLV3 feedback loop and SAM size.more » « less
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