The Effect of Cr Addition on the Strength and High Temperature Oxidation Resistance of Y2O3 Dispersion Strengthened Mo Composites.

Y2O3 dispersion-strengthened Molybdenum (Mo) composites were prepared by the mechanical alloying of Mo and Y powders then consolidation by spark plasma sintering. The effects of Chromium (Cr) addition (0 wt. %, 5 wt. %, 10 wt. % and 15 wt. %, respectively) on the mechanical performance and high-temperature oxidation resistance of Mo-Y2O3 were investigated. The introduction of Cr had a significant influence on the mechanical property and oxidation resistance of the Mo-Y2O3 composite. The highest bending strength reached 932 MPa when the addition of Cr content was 5 wt. % (Mo-5Cr-1Y sample). This improvement is likely attributable to the dual mechanism of grain refinement and solid solution strengthening. Moreover, the Mo-5Cr-1Y sample showed the thinnest oxide layer thickness after high-temperature oxidation tests, and exhibited the best oxidation resistance performance compared with the other samples. First principle calculation reveals that Cr could improve the Mo-MoO3 interface bonding to prevent rapid spalling of the oxide layer. Meanwhile, Cr also facilitates the formation of the dense Cr2(MoO4)3 layer on the surface, which can inhibit further oxidation.

Enhancement of spectral model transferability in LIBS systems through LIBS-LIPAS fusion technique.

BACKGROUND: Laser-induced breakdown spectroscopy (LIBS) is extensively utilized a range of scientific and industrial detection applications owing to its capability for rapid, in-situ detection. However, conventional LIBS models are often tailored to specific LIBS systems, hindering their transferability between LIBS subsystems. Transfer algorithms can adapt spectral models to subsystems, but require access to the datasets of each subsystem beforehand, followed by making individual adjustments for the dataset of each subsystem. It is clear that a method to enhance the inherent transferability of spectral original models is urgently needed. RESULTS: We proposed an innovative fusion methodology, named laser-induced breakdown spectroscopy fusion laser-induced plasma acoustic spectroscopy (LIBS-LIPAS), to enhance the transferability of support vector machine (SVM) original models across LIBS systems with varying laser beams. The methodology was demonstrated using nickel-based high-temperature alloy samples. Here, the area-full width at half maximum (AFCEI) Composite Evaluation Index was proposed for extracting critical features from LIBS. Further enhancing the transferability of the model, the laser-induced plasma acoustic signal was transformed from the time domain to the frequency domain. Subsequently, the feature-level fusion method was employed to improve the classification accuracy of the transferred LIBS system to 97.8 %. A decision-level fusion approach (amalgamating LIBS, LIPAS, and feature-level fusion models) achieved an exemplary accuracy of 99 %. Finally, the adaptability of the method was demonstrated using titanium alloy samples. SIGNIFICANCE AND NOVELTY: In this work, based on plasma radiation models, we simultaneously captured LIBS and LIPAS, and proposed the fusion of these two distinct yet origin-consistent signals, significantly enhancing the transferability of the LIBS original model. The methodology proposed holds significant potential to advance LIBS technology and broaden its applicability in analytical chemistry research and industrial applications.

Knockout of transcription factor OsERF65 enhances ROS scavenging ability and confers resistance to rice sheath blight.

Rice sheath blight (ShB) is a devastating disease that severely threatens rice production worldwide. Induction of cell death represents a key step during infection by the ShB pathogen Rhizoctonia solani. Nonetheless, the underlying mechanisms remain largely unclear. In the present study, we identified a rice transcription factor, OsERF65, that negatively regulates resistance to ShB by suppressing cell death. OsERF65 was significantly upregulated by R. solani infection in susceptible cultivar Lemont and was highly expressed in the leaf sheath. Overexpression of OsERF65 (OsERF65OE) decreased rice resistance, while the knockout mutant (oserf65) exhibited significantly increased resistance against ShB. The transcriptome assay revealed that OsERF65 repressed the expression of peroxidase genes after R. solani infection. The antioxidative enzyme activity was significantly increased in oserf65 plants but reduced in OsERF65OE plants. Consistently, hydrogen peroxide content was apparently reduced in oserf65 plants but accumulated in OsERF65OE plants. OsERF65 directly bound to the GCC box in the promoter regions of four peroxidase genes and suppressed their transcription, reducing the ability to scavenge reactive oxygen species (ROS). The oserf65 mutant exhibited a slight decrease in plant height but increased grain yield. Overall, our results revealed an undocumented role of OsERF65 that acts as a crucial regulator of rice resistance to R. solani and a potential target for improving both ShB resistance and rice yield.

A comprehensive overview of cotton genomics, biotechnology and molecular biological studies.

Cotton is an irreplaceable economic crop currently domesticated in the human world for its extremely elongated fiber cells specialized in seed epidermis, which makes it of high research and application value. To date, numerous research on cotton has navigated various aspects, from multi-genome assembly, genome editing, mechanism of fiber development, metabolite biosynthesis, and analysis to genetic breeding. Genomic and 3D genomic studies reveal the origin of cotton species and the spatiotemporal asymmetric chromatin structure in fibers. Mature multiple genome editing systems, such as CRISPR/Cas9, Cas12 (Cpf1) and cytidine base editing (CBE), have been widely used in the study of candidate genes affecting fiber development. Based on this, the cotton fiber cell development network has been preliminarily drawn. Among them, the MYB-bHLH-WDR (MBW) transcription factor complex and IAA and BR signaling pathway regulate the initiation; various plant hormones, including ethylene, mediated regulatory network and membrane protein overlap fine-regulate elongation. Multistage transcription factors targeting CesA 4, 7, and 8 specifically dominate the whole process of secondary cell wall thickening. And fluorescently labeled cytoskeletal proteins can observe real-time dynamic changes in fiber development. Furthermore, research on the synthesis of cotton secondary metabolite gossypol, resistance to diseases and insect pests, plant architecture regulation, and seed oil utilization are all conducive to finding more high-quality breeding-related genes and subsequently facilitating the cultivation of better cotton varieties. This review summarizes the paramount research achievements in cotton molecular biology over the last few decades from the above aspects, thereby enabling us to conduct a status review on the current studies of cotton and provide strong theoretical support for the future direction.

Visualization of Cytoskeleton Organization and Dynamics in Elongating Cotton Fibers by Live-Cell Imaging.

Cotton fibers are extremely elongated single cells and have long been regarded as an ideal model to investigate polarized plant cell elongation. Actin filaments (F-actin), as well as the cortical microtubules (CMTs), play vital roles in polarized cell growth and morphogenesis. We have generated stable transgenic cotton plants expressing fluorescent markers for the actin and microtubule cytoskeletons. Further live-cell imaging identified dynamic features of the F-actin and cortical microtubule (CMT) architectures and discovered that cotton fibers elongate in a unique tip-biased diffuse growth mode. Here, we describe methods for preparing growing cotton fiber samples, as well as the visualization of cytoskeletal organization and dynamics by live-cell imaging. Combined with comprehensive image analyses, these methods can be used to identify how cytoskeleton organization and dynamics determine cell morphogenesis in highly polarized cotton fibers.

Brassinosteroid signals cooperate with katanin-mediated microtubule severing to control stamen filament elongation.

Proper stamen filament elongation is essential for pollination and plant reproduction. Plant hormones are extensively involved in every stage of stamen development; however, the cellular mechanisms by which phytohormone signals couple with microtubule dynamics to control filament elongation remain unclear. Here, we screened a series of Arabidopsis thaliana mutants showing different microtubule defects and revealed that only those unable to sever microtubules, lue1 and ktn80.1234, displayed differential floral organ elongation with less elongated stamen filaments. Prompted by short stamen filaments and severe decrease in KTN1 and KTN80s expression in qui-2 lacking five BZR1-family transcription factors (BFTFs), we investigated the crosstalk between microtubule severing and brassinosteroid (BR) signaling. The BFTFs transcriptionally activate katanin-encoding genes, and the microtubule-severing frequency was severely reduced in qui-2. Taken together, our findings reveal how BRs can regulate cytoskeletal dynamics to coordinate the proper development of reproductive organs.

Verticillium dahliae Asp1 regulates the transition from vegetative growth to asexual reproduction by modulating microtubule dynamic organization.

Verticillium dahliae is a devastating pathogenic fungus that causes severe vascular wilts in more than 400 dicotyledonous plants. The conidiation of V. dahliae in plant vascular tissues is the key strategy for its adaptation to the nutrient-poor environment and is required for its pathogenicity. However, it remains unclear about the regulatory mechanism of conidium production of V. dahliae in vascular tissues. Here, we found that VdAsp1, encoding an inositol polyphosphate kinase, is indispensable for the pathogenicity of V. dahliae. Loss of VdAsp1 function does not affect the invasion of the host, but it impairs the colonization and proliferation in vascular tissues. The ΔVdAsp1 mutant shows defective initiation of conidiophore formation and reduced expression of genes associated with the central developmental pathway. By live-cell imaging, we observed that some of ΔVdAsp1 mutant hyphae are swollen, and microtubule arrangements at the apical region of these hyphae are disorganized. These results indicate that VdAsp1 regulates the transition from vegetative growth to asexual reproduction by modulating microtubule dynamic organization, which is essential for V. dahliae to colonize and proliferate in vascular tissues. These findings provided a potential new direction in the control of vascular wilt pathogen by targeting conidium production in vascular tissues.

Exogenous melatonin enhances cell wall response to salt stress in common bean (Phaseolus vulgaris) and the development of the associated predictive molecular markers.

Common bean (Phaseolus vulgaris) is an important food crop; however, its production is affected by salt stress. Salt stress can inhibit seed germination, promote senescence, and modify cell wall biosynthesis, assembly, and architecture. Melatonin, an indole heterocycle, has been demonstrated to greatly impact cell wall structure, composition, and regulation in plants under stress. However, the molecular basis for such assumptions is still unclear. In this study, a common bean variety, "Naihua" was treated with water (W), 70 mmol/L NaCl solution (S), and 100 µmol/L melatonin supplemented with salt solution (M+S) to determine the response of common bean to exogenous melatonin and explore regulatory mechanism of melatonin against salt stress. The results showed that exogenous melatonin treatment alleviated salt stress-induced growth inhibition of the common bean by increasing the length, surface area, volume, and diameter of common bean sprouts. Moreover, RNA sequencing (RNA-seq) and real-time quantitative PCR (qRT-PCR) indicated that the cell wall regulation pathway was involved in the salt stress tolerance of the common bean enhanced by melatonin. Screening of 120 germplasm resources revealed that melatonin treatment improved the salt tolerance of more than 65% of the common bean germplasm materials. Melatonin also up-regulated cell wall pathway genes by at least 46%. Furthermore, we analyzed the response of the common bean germplasm materials to melatonin treatment under salt stress using the key genes associated with the synthesis of the common bean cell wall as the molecular markers. The results showed that two pairs of markers were significantly associated with melatonin, and these could be used as candidate markers to predict whether common bean respond to exogenous melatonin and then enhance salt tolerance at the sprouting stage. This study shows that cell wall can respond to exogenous melatonin and enhance the salt tolerance of common bean. The makers identified in this study can be used to select common bean varieties that can respond to melatonin under stress. Overall, the study found that cell wall could response melatonin and enhance the salt tolerance and developed the makers for predicting varieties fit for melatonin under stress in common bean, which may be applied in the selection or development of common bean varieties with abiotic stress tolerance.

A legume kinesin controls vacuole morphogenesis for rhizobia endosymbiosis.

Symbioses between legumes and rhizobia require establishment of the plant-derived symbiosome membrane, which surrounds the rhizobia and accommodates the symbionts by providing an interface for nutrient and signal exchange. The host cytoskeleton and endomembrane trafficking systems play central roles in the formation of a functional symbiotic interface for rhizobia endosymbiosis; however, the underlying mechanisms remain largely unknown. Here we demonstrate that the nodulation-specific kinesin-like calmodulin-binding protein (nKCBP), a plant-specific microtubule-based kinesin motor, controls central vacuole morphogenesis in symbiotic cells in Medicago truncatula. Phylogenetic analysis further indicated that nKCBP duplication occurs solely in legumes of the clade that form symbiosomes. Knockout of nKCBP results in central vacuole deficiency, defective symbiosomes and abolished nitrogen fixation. nKCBP decorates linear particles along microtubules, and crosslinks microtubules with the actin cytoskeleton, to control central vacuole formation by modulating vacuolar vesicle fusion in symbiotic cells. Together, our findings reveal that rhizobia co-opted nKCBP to achieve symbiotic interface formation by regulating cytoskeletal assembly and central vacuole morphogenesis during nodule development.

Exogenous melatonin enhances soybean (Glycine max (L.) Merr.) seedling tolerance to saline-alkali stress by regulating antioxidant response and DNA damage repair.

Saline-alkali (SA) stress induces excessive reactive oxygen species (ROS) accumulation in plant cells, resulting in oxidative damages of membranes, lipids, proteins, and nucleic acids. Melatonin has antioxidant protection effects in living organisms and thus has received a lot of attention. This study aimed to investigate the effect and regulating mechanism of melatonin treatment on soybean tolerance to SA stress. In this study, cultivars Heihe 49 (HH49, SA-tolerant) and Henong 95 (HN95, SA-sensitive) were pot-cultured in SA soil, then treated with MT (0-300 µM) at V1 stage. SA stress induced ROS accumulation and DNA damage in the seedling roots of both cultivars, causing G1/S arrest in HN95 and G2/M arrest in HH49. Melatonin treatment enhanced the activity of antioxidant enzymes in soybean seedling roots and reduced ROS accumulation. Additionally, melatonin treatment upregulated DNA damage repair genes, thus enhancing the reduction of DNA oxidative damage under SA stress. The effects of melatonin treatment were manifested as decreased RAPD polymorphism, 8-hydroxy-2'-deoxyguanine (8-OH-dG) level, and relative density of apurinic sites (AP-sites). Meanwhile, melatonin treatment partially alleviated the SA-induced G1/S arrest in HN95 and G2/M arrest in HH49, thus enhancing soybean seedling tolerance to SA stress.

Suppressing chlorophyll degradation by silencing OsNYC3 improves rice resistance to Rhizoctonia solani, the causal agent of sheath blight.

Necrotrophic fungus Rhizoctonia solani Kühn (R. solani) causes serious diseases in many crops worldwide, including rice and maize sheath blight (ShB). Crop resistance to the fungus is a quantitative trait and resistance mechanism remains largely unknown, severely hindering the progress on developing resistant varieties. In this study, we found that resistant variety YSBR1 has apparently stronger ability to suppress the expansion of R. solani than susceptible Lemont in both field and growth chamber conditions. Comparison of transcriptomic profiles shows that the photosynthetic system including chlorophyll biosynthesis is highly suppressed by R. solani in Lemont but weakly in YSBR1. YSBR1 shows higher chlorophyll content than that of Lemont, and inducing chlorophyll degradation by dark treatment significantly reduces its resistance. Furthermore, three rice mutants and one maize mutant that carry impaired chlorophyll biosynthesis all display enhanced susceptibility to R. solani. Overexpression of OsNYC3, a chlorophyll degradation gene apparently induced expression by R. solani infection, significantly enhanced ShB susceptibility in a high-yield ShB-susceptible variety '9522'. However, silencing its transcription apparently improves ShB resistance without compromising agronomic traits or yield in field tests. Interestingly, altering chlorophyll content does not affect rice resistance to blight and blast diseases, caused by biotrophic and hemi-biotrophic pathogens, respectively. Our study reveals that chlorophyll plays an important role in ShB resistance and suppressing chlorophyll degradation induced by R. solani infection apparently improves rice ShB resistance. This discovery provides a novel target for developing resistant crop to necrotrophic fungus R. solani.

Corrigendum: Contrast-Enhanced CT-Based Radiomics Analysis in Predicting Lymphovascular Invasion in Esophageal Squamous Cell Carcinoma.

[This corrects the article DOI: 10.3389/fonc.2021.644165.].

Identification of a Novel Immune-Related CpG Methylation Signature to Predict Prognosis in Stage II/III Colorectal Cancer.

With the increasing incidence of colorectal cancer (CRC) and continued difficulty in treating it using immunotherapy, there is an urgent need to identify an effective immune-related biomarker associated with the survival and prognosis of patients with this disease. DNA methylation plays an essential role in maintaining cellular function, and changes in methylation patterns may contribute to the development of autoimmunity, aging, and cancer. In this study, we aimed to identify a novel immune-related methylated signature to aid in predicting the prognosis of patients with CRC. We investigated DNA methylation patterns in patients with stage II/III CRC using datasets from The cancer genome atlas (TCGA). Overall, 182 patients were randomly divided into training (n = 127) and test groups (n = 55). In the training group, five immune-related methylated CG sites (cg11621464, cg13565656, cg18976437, cg20505223, and cg20528583) were identified, and CG site-based risk scores were calculated using univariate Cox proportional hazards regression in patients with stage II/III CRC. Multivariate Cox regression analysis indicated that methylated signature was independent of other clinical parameters. The Kaplan-Meier analysis results showed that CG site-based risk scores could significantly help distinguish between high- and low-risk patients in both the training (P = 0.000296) and test groups (P = 0.022). The area under the receiver operating characteristic curve in the training and test groups were estimated to be 0.771 and 0.724, respectively, for prognosis prediction. Finally, stratified analysis results suggested the remarkable prognostic value of CG site-based risk scores in CRC subtypes. We identified five methylated CG sites that could be used as an efficient overall survival (OS)-related biomarker for stage II/III CRC patients.

Contrast-Enhanced CT-Based Radiomics Analysis in Predicting Lymphovascular Invasion in Esophageal Squamous Cell Carcinoma.

OBJECTIVES: To develop a radiomics model based on contrast-enhanced CT (CECT) to predict the lymphovascular invasion (LVI) in esophageal squamous cell carcinoma (ESCC) and provide decision-making support for clinicians. PATIENTS AND METHODS: This retrospective study enrolled 334 patients with surgically resected and pathologically confirmed ESCC, including 96 patients with LVI and 238 patients without LVI. All enrolled patients were randomly divided into a training cohort and a testing cohort at a ratio of 7:3, with the training cohort containing 234 patients (68 patients with LVI and 166 without LVI) and the testing cohort containing 100 patients (28 patients with LVI and 72 without LVI). All patients underwent preoperative CECT scans within 2 weeks before operation. Quantitative radiomics features were extracted from CECT images, and the least absolute shrinkage and selection operator (LASSO) method was applied to select radiomics features. Logistic regression (Logistic), support vector machine (SVM), and decision tree (Tree) methods were separately used to establish radiomics models to predict the LVI status in ESCC, and the best model was selected to calculate Radscore, which combined with two clinical CT predictors to build a combined model. The clinical model was also developed by using logistic regression. The receiver characteristic curve (ROC) and decision curve (DCA) analysis were used to evaluate the model performance in predicting the LVI status in ESCC. RESULTS: In the radiomics model, Sphericity and gray-level non-uniformity (GLNU) were the most significant radiomics features for predicting LVI. In the clinical model, the maximum tumor thickness based on CECT (cThick) in patients with LVI was significantly greater than that in patients without LVI (P<0.001). Patients with LVI had higher clinical N stage based on CECT (cN stage) than patients without LVI (P<0.001). The ROC analysis showed that both the radiomics model (AUC values were 0.847 and 0.826 in the training and testing cohort, respectively) and the combined model (0.876 and 0.867, respectively) performed better than the clinical model (0.775 and 0.798, respectively), with the combined model exhibiting the best performance. CONCLUSIONS: The combined model incorporating radiomics features and clinical CT predictors may potentially predict the LVI status in ESCC and provide support for clinical treatment decisions.

miR-155-5p regulates macrophage M1 polarization and apoptosis in the synovial fluid of patients with knee osteoarthritis.

Osteoarthritis (OA) is one of the most prevalent degenerative joint diseases that affects millions of individuals worldwide. During OA, proinflammatory factors (including IL-1, IL-6, IL-17 and TNF-α) are released from chondrocytes and proliferating synoviocytes potentiate the proinflammatory microenvironment of the synovial fluid (SF). The altered SF microenvironment affects the infiltration, polarization and apoptosis of macrophages, though the underlying mechanisms are not completely understood. In the present study, the hypothesis that the knee synovial fluid of patients with knee osteoarthritis (KOA SF) promotes the polarization of peripheral blood mononuclear cell (PBMC)-derived M1 macrophages and inhibits PBMC-derived macrophage apoptosis was investigated. KOA SF increased PBMC-derived macrophage M1 polarization via the microRNA (miR)-155-5p/suppressor of cytokine signaling 1 signaling pathway. Caspase-3 (CASP3) was identified as a novel target of miR-155-5p, where KOA SF inhibited macrophage apoptosis via the miR-155-5p/CASP3 signaling pathway. The results suggested that the proinflammatory environment of KOA SF promoted macrophage M1 polarization and reduced macrophage apoptosis via miR-155-5p. The results provided a potential explanation for the increased number of M1 macrophages observed in KOA SF during OA. In addition, the present study suggested that miR-155-5p may serve as a potential therapeutic target for KOA.

FERONIA mediates root nutating growth.

Root nutation indicates the behavior that roots grow in a waving and skewing way due to unequal growth rates on different sides. Although a few developmental and environmental factors have been reported, genetic pathways mediating this process are obscure. We report here that the Arabidopsis CrRLK1L family member FERONIA (FER) is critical for root nutation. Functional loss of FER resulted in enhanced root waviness on tilted plates or roots forming anti-clockwise coils on horizontal plates. Suppressing polar auxin transport, either by pharmacological treatment or by introducing mutations at PIN-FORMED2 (PIN2) or AUXIN RESISTANT1 (AUX1), suppressed the asymmetric root growth (ARG) in fer-4, a null mutant of FER, indicating that FER suppression of ARG depends on polar auxin transport. We further showed by pharmacological treatments that dynamic microtubule organization and Ca2+ signaling are both critical for FER-mediated ARG. Results presented here demonstrate a key role of FER in mediating root nutating growth, through PIN2- and AUX1-mediated auxin transport, through dynamic microtubule organization, and through Ca2+ signaling.

Application of CT images in the diagnosis of lung cancer based on finite mixed model.

Investigating the application of CT images when diagnosing lung cancer based on finite mixture model is the objective. METHOD: 120 clean healthy rats were taken as the research objects to establish lung cancer rat model and carry out lung CT image examination. After the successful CT image data preprocessing, the image is segmented by different methods, which include lung nodule segmentation on the basis of Adaptive Particle Swarm Optimization - Gaussian mixture model (APSO-GMM), lung nodule segmentation on the basis of Adaptive Particle Swarm Optimization - gamma mixture model (APSO-GaMM), lung nodule segmentation based on statistical information and self-selected mixed distribution model, and lung nodule segmentation based on neighborhood information and self-selected mixed distribution model. The segmentation effect is evaluated. RESULTS: Compared with the results of lung nodule segmentation based on statistical information and self-selected mixed distribution model, the Dice coefficient of lung nodule segmentation based on neighborhood information and self-selected mixed distribution model is higher, the relative final measurement accuracy is smaller, the segmentation is more accurate, but the running time is longer. Compared with APSO-GMM and APSO-GaMM, the dice value of self-selected mixed distribution model segmentation method is larger, and the final measurement accuracy is smaller. CONCLUSION: Among the five methods, the dice value of the self-selected mixed distribution model based on neighborhood information is the largest, and the relative accuracy of the final measurement is the smallest, indicating that the segmentation effect of the self-selected mixed distribution model based on neighborhood information is the best.

miR­204 inhibits the osteogenic differentiation of mesenchymal stem cells by targeting bone morphogenetic protein 2.

Mesenchymal stem cells (MSCs) are used to investigate regeneration and differentiation. MicroRNA­204 (miR­204) in involved in the Runt­related transcription factor 2/alkaline phosphatase/bone morphogenic protein 2 (Runx2/ALP/BMP2) signaling pathway that regulates bone marrow mesenchymal stem cell (BMSC) differentiation; however, the mechanisms underlying the effects of miR­204 are yet to be determined. The aim of the present study was to investigate the effects of miR­204 on BMSC differentiation. BMSCs were derived from rat bone marrow. The expression levels of Runx2, ALP and BMP2 were measured via reverse transcription­quantitative polymerase chain reaction and western blot analyses following transfection of BMSCs with miR­204 agomir or BMP2 expression vector. The ability of the miR­204 gene to directly bind BMP2 mRNA was assessed using dual­luciferase assays. Ossification was measured via alizarin red stain assays. It was observed that the expression levels of Runx2 and ALP increased over time, whereas those of miR­204 decreased; additionally, miR­204 agomir upregulation inhibited the expression of Runx2, ALP and BMP2 in BMSCs. It was revealed that miR­204 directly interacted with BMP2 mRNA, and that transfection with miR­204 agomir suppressed ossification in BMSCs by targeting the BMP2/Runx2/ALP signaling pathway.

Live-cell imaging of the cytoskeleton in elongating cotton fibres.

Cotton (Gossypium hirsutum) fibres consist of single cells that grow in a highly polarized manner, assumed to be controlled by the cytoskeleton1-3. However, how the cytoskeletal organization and dynamics underpin fibre development remains unexplored. Moreover, it is unclear whether cotton fibres expand via tip growth or diffuse growth2-4. We generated stable transgenic cotton plants expressing fluorescent markers of the actin and microtubule cytoskeleton. Live-cell imaging revealed that elongating cotton fibres assemble a cortical filamentous actin network that extends along the cell axis to finally form actin strands with closed loops in the tapered fibre tip. Analyses of F-actin network properties indicate that cotton fibres have a unique actin organization that blends features of both diffuse and tip growth modes. Interestingly, typical actin organization and endosomal vesicle aggregation found in tip-growing cell apices were not observed in fibre tips. Instead, endomembrane compartments were evenly distributed along the elongating fibre cells and moved bi-directionally along the fibre shank to the fibre tip. Moreover, plus-end tracked microtubules transversely encircled elongating fibre shanks, reminiscent of diffusely growing cells. Collectively, our findings indicate that cotton fibres elongate via a unique tip-biased diffuse growth mode.

Towards a better recording of microtubule cytoskeletal spatial organization and dynamics in plant cells.

Numerous fluorescent marker lines are currently available to visualize microtubule (MT) architecture and dynamics in living plant cells, such as markers expressing p35S::GFP-MBD or p35S::GFP-TUB6. However, these MT marker lines display obvious defects that affect plant growth or produce unstable fluorescent signals. Here, a series of new marker lines were developed, including the pTUB6::VisGreen-TUB6-expressing line in which TUB6 is under the control of its endogenous regulatory elements and eGFP is replaced with VisGreen, a brighter fluorescent protein. Moreover, two different markers were combined into one expression vector and developed two dual-marker lines. These marker lines produce bright, stable fluorescent signals in various tissues, and greatly shorten the screening process for generating dual-marker lines. These new marker lines provide a novel resource for MT research.