No abstract

Plant interphase cortical microtubules (cMTs) mediate anisotropic cell expansion in response to environmental and developmental cues. In Arabidopsis thaliana, KATANIN 1 (KTN1), the p60 catalytic subunit of the conserved MT‐severing enzyme katanin, is essential for cMT ordering and anisotropic cell expansion. However, the regulation of KTN1‐mediated cMT severing and ordering remains unclear. In this work, we report that the Arabidopsis IQ67 DOMAIN (IQD) family gene ABNORMAL SHOOT 6 (ABS6) encodes a MT‐associated protein. Overexpression of ABS6 leads to elongated cotyledons, directional pavement cell expansion, and highly ordered transverse cMT arrays. Genetic suppressor analysis revealed that ABS6‐mediated cMT ordering is dependent on KTN1 and SHADE AVOIDANCE 4 (SAV4). Live imaging of cMT dynamics showed that both ABS6 and SAV4 function as positive regulators of cMT severing. Furthermore, ABS6 directly interacts with KTN1 and SAV4 and promotes their recruitment to the cMTs. Finally, analysis of loss‐of‐function mutant combinations showed that ABS6, SAV4, and KTN1 work together to ensure the robust ethylene response in the apical hook of dark‐grown seedlings. Together, our findings establish ABS6 and SAV4 as positive regulators of cMT severing and ordering, and highlight the role of cMT dynamics in fine‐tuning differential growth in plants.

The potential risks of x-ray to patients have transferred the public’s attention from normal dose CT (NDCT) to low-dose CT (LDCT). However, simply lowering the radiation dose of the CT system will significantly degrade the quality of CT images such as noise and artifacts, which compromises the diagnostic performance. Hence, various methods have been proposed to solve this problem over the past decades. Although these methods have achieved impressive results, they also suffer from a drawback of smoothing image details after denoising, which makes it difficult for clinical diagnosis and treatment. To address this issue, this paper introduces a novel gradient regularization method for LDCT enhancement. Rather than common methods which only consider the pixel-wise gray value loss in the reconstruction procedure, we also take the image gradient loss into consideration to preserve image details. By combining the gradient regularization method and the convolutional neural network (CNN) framework, a gradient regularized convolutional neural network (GRCNN) is proposed to enhance LDCT images which has achieved promising performance in our experiments both visually and quantitatively.

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The MAP215 family of microtubule (MT) polymerase/nucleation factors and the MT severing enzyme katanin are widely conserved microtubule-associated proteins (MAPs) across the plant and animal kingdoms. However, how these two essential MAPs coordinate to regulate plant MT dynamics and development remains unknown. Here, we identified novel hypomorphic alleles of MICROTUBULE ORGANIZATION 1 (MOR1), encoding the Arabidopsis thaliana homolog of MAP215, in genetic screens for mutants oversensitive to the MT-destabilizing drug propyzamide. Live imaging in planta revealed that MOR1-green fluorescent protein (GFP) predominantly tracks the plus-ends of cortical MTs in interphase cells and labels preprophase band, spindle and phragmoplast MT arrays in diving cells. Remarkably, MOR1 and KATANIN 1 (KTN1), the p60 subunit of Arabidopsis katanin, act synergistically to control the proper formation of plant-specific MT arrays, and consequently, cell division and anisotropic cell expansion. Moreover, MOR1 physically interacts with KTN1 and promotes KTN1-mediated severing of cortical MTs. Our work establishes the Arabidopsis MOR1-KTN1 interaction as a central functional node dictating MT dynamics and plant growth and development.