Role of Orphan ParA Proteins in Replication and Cell Division in Rhodococcus erythropolis PR4.

Bacteria have a very well-regulated mechanism for chromosome segregation and cell division. This process requires a large number of complex proteins to participate and mediate their functionality. Among these complex proteins, ParA and ParB play a vital role for the faithful segregation of chromosome. In Rhodococcus erythropolis PR4, besides the essential parAB operon, there are three orphan copies of parA genes. Here, we report that the orphan ParA2 and ParA3 have distinct roles in the cell cycle. The disruption of the orphan parA2 or parA3 gene resulted in elongated cells. Multiple septal rings and mislocalised septa were observed in ΔparA3 and ΔparA2 mutants, respectively. The subcellular localization of ParA2 revealed a distinct ring- and ribbon-like structure. On the other hand, orphan ParA3 was localized slightly away from the poles. The orphan ParA proteins were found to interact with ParB, the strongest interaction was observed with ParA2. Further, asynchronous replication initiation was observed in ΔparA3 mutants suggesting its role in replication. This is the first report demonstrating the distinct roles of orphan parA genes from Rhodococcus.

Measurable morphological features of single circulating tumor cells in selected solid tumors-A pilot study.

Liquid biopsies developed into a range of sensitive technologies aiming to analyze for example, circulating tumor cells (CTCs) in peripheral blood, which significantly deepens understanding of the metastatic process. Nevertheless, examination of CTCs is mostly limited to their enumeration and usually only 2-3 markers-based phenotyping, not offering yet sufficient insight into their biology. In contrast, quantitative analysis of their morphological details might extend our knowledge about dissemination and even improve CTC isolation or label-free identification methods dependent on their physical features such as size, and deformability. Current study was conducted to describe CTCs' and their size, shape, presence of protrusions, and micronuclei across various types of cancers (lung, n = 29; ovarian, n = 24, breast, n = 54; and prostate, n = 33). Epithelial (pan-keratins), mesenchymal (vimentin), and two exclusion markers were used to identify CTCs and classify them into four epithelial and epithelial-mesenchymal transition-related phenotypes using standardized and throughput method, imaging flow cytometry. The morphological characteristics of CTCs, including their nuclei, such as circularity, the maximum, and minimum diagonal values were determined using an open-source software QuPath. On average, detected CTCs (n = 1156) were larger, and more irregular in shape compared to leukocytes/endothelial cells (n = 400). Epithelial and mesenchymal CTCs had the largest (median = 18.2 µm) and the smallest diameter (median = 10.4 µm), respectively. In terms of cancer-specific variations, the largest CTCs were identified in lung cancer, whereas the smallest-in prostate and breast cancers. Epithelial CTCs and those negative for both epithelial and mesenchymal markers exhibited the highest degree of elongation, whereas mesenchymal CTCs were the most irregular in shape. Protrusions and micronuclei were observed extremely rarely within CTCs of breast and prostate cancer (0.6%-0.8% of CTCs). Micronuclei were observed only in epithelial and epithelial-mesenchymal CTCs. This study underscores the significant variability in the morphological features of CTCs in relation to their phenotypic classification or even the particular organ of origin, potentially influencing for example, size-dependent CTC isolation methods. It demonstrates for the first time the morphological measurements of CTCs undergoing epithelial-mesenchymal transition, and some specific morphological details (i.e., protrusions, micronuclei) within CTCs in general.

Roles of Histone Acetylation and Deacetylation in Root Development.

Roots are usually underground plant organs, responsible for anchoring to the soil, absorbing water and nutrients, and interacting with the rhizosphere. During root development, roots respond to a variety of environmental signals, contributing to plant survival. Histone post-translational modifications play essential roles in gene expression regulation, contributing to plant responses to environmental cues. Histone acetylation is one of the most studied post-translational modifications, regulating numerous genes involved in various biological processes, including development and stress responses. Although the effect of histone acetylation on plant responses to biotic and abiotic stimuli has been extensively reviewed, no recent reviews exist focusing on root development regulation by histone acetylation. Therefore, this review brings together all the knowledge about the impact of histone acetylation on root development in several plant species, mainly focusing on Arabidopsis thaliana. Here, we summarize the role of histone acetylation and deacetylation in numerous aspects of root development, such as stem cell niche maintenance, cell division, expansion and differentiation, and developmental zone determination. We also emphasize the gaps in current knowledge and propose new perspectives for research toward deeply understanding the role of histone acetylation in root development.

Synergistic effect of the combination of phenolic compounds and tobramycin on the inhibition of Pseudomonas aeruginosa biofilm.

Bacteria coordinate gene expression in a cell density-dependent manner using a communication process called quorum sensing (QS). The expression of virulence factors, biofilm formation and enzyme production are examples of QS-regulated phenotypes that can interfere with food quality and safety. Due to the importance of these phenotypes, the inhibition of bacterial communication as an anti-virulence strategy is of great interest. This work aimed to evaluate the effect of phenolic compounds on the inhibition of biofilm formation by Pseudomonas aeruginosa PAO1, using concentrations that do not interfere in bacterial growth. The synergistic effect of rosmarinic acid, baicalein, curcumin and resveratrol with tobramycin and between the phenolics themselves was evaluated. The tested combinations proved to be a good strategy for reducing the dose of antibiotics used in treatments and obtaining satisfactory results against P. aeruginosa biofilms. The combination of the four compounds at the highest concentration (500 µM) completely inhibited biofilm formation. The obtained results contribute to understanding the effect of phenolic compounds on QS inhibition, which may help to define the mechanism of inhibition, in addition to expanding the biotechnological potential of these compounds for future applications in the food, pharmaceutical and medical fields.

Transcriptional regulation of phospholipid transport in cotton fiber elongation by GhMYB30D04-GhHD1 interaction complex.

Cotton fiber length is basically determined by well-coordinated gene expression and phosphatidylinositol phosphates (PIPs) accumulation during fiber elongation but the regulatory mechanism governing PIPs transport remains unknown. Here, we report a MYB transcription factor GhMYB30D04 in Gossypium hirsutum that promotes fiber elongation through modulating the expression of PIP transporter gene GhLTPG1. Knockout of GhMYB30D04 gene in cotton (KO) results in a reduction of GhLTPG1 transcripts with lower accumulation of PIPs, leading to shorter fibers and lower fiber yield. Conversely, GhMYB30D04 overexpression (GhMYB30D04-OE) causes richer PIPs and longer cotton fibers, mimicking the effects of exogenously applying PIPs on the ovules of GhMYB30D04-KO and wild type. Furthermore, GhMYB30D04 interacts with GhHD1, the crucial transcription factor of fiber initiation, to form an activation complex stabilized by PIPs, both of which upregulate GhLTPG1 expression. Comparative omics-analysis revealed that higher and extended expressions of LTPG1 in fiber elongation mainly correlate with the variations of the GhMYB30D04 gene between two cotton allotetraploids, contributing to longer fiber in G. babardense. Our work clarifies a mechanism by which GhHD1-GhMYB30D04 form a regulatory module of fiber elongation to tightly control PIP accumulation. Our work still has an implication that GhMYB30D04-GhHD1 associates with development transition from fiber initiation to elongation.

Carnivorous Nepenthes pitcher plants combine common developmental processes to make a complex epidermal trapping surface.

BACKGROUND AND AIMS: A hierarchical micro-topography of ridges and steps renders the trap rim of carnivorous Nepenthes pitcher plants unusually wettable, and slippery for insects when wet. This complex three-dimensional epidermis structure forms, hidden from plain sight, inside the still-closed developing pitcher bud. Here, we reveal the sequence of epidermal patterning events that shape the trap rim. By linking this sequence to externally visible markers of bud development, we provide a framework for targeting individual stages of surface development in future studies. METHODS: We used cryo-scanning electron microscopy to investigate the detailed morphogenesis and epidermal patterning of the Nepenthes x hookeriana pitcher rim. In addition, we collected morphometric and qualitative data from developing pitcher traps including those sampled for microscopy. KEY RESULTS: We identified three consecutive patterning events. First, strictly oriented cell divisions resulted in radially aligned rows of cells and established a macroscopic ridge-and-groove pattern. Next, conical papillate cells formed, and papillae elongated towards the trap interior, increasingly overlapping adjacent cells and eventually forming continuous microscopic ridges. In between these ridges, the flattened papillae formed acutely angled arched steps. Finally, the cells elongated radially, thereby establishing the convex collar shape of the rim. This general sequence of surface development also showed a spatial progression from the outer to the inner trap rim edge, with several consecutive developmental stages co-occurring at any given time. CONCLUSIONS: We demonstrate that the complex surface microtopography of the Nepenthes pitcher rim develops by sequentially combining widespread, evolutionarily conserved epidermal patterning processes in a new way. This makes the Nepenthes trap rim an excellent model for studying epidermal patterning mechanisms in leaves.

DivIVA controls the dynamics of septum splitting and cell elongation in Streptococcus pneumoniae.

Bacterial shape and division rely on the dynamics of cell wall assembly, which involves regulated synthesis and cleavage of the peptidoglycan. In ovococci, these processes are coordinated within an annular mid-cell region with nanometric dimensions. More precisely, the cross-wall synthesized by the divisome is split to generate a lateral wall, whose expansion is insured by the insertion of the so-called peripheral peptidoglycan by the elongasome. Septum cleavage and peripheral peptidoglycan synthesis are, thus, crucial remodeling events for ovococcal cell division and elongation. The structural DivIVA protein has long been known as a major regulator of these processes, but its mode of action remains unknown. Here, we integrate click chemistry-based peptidoglycan labeling, direct stochastic optical reconstruction microscopy, and in silico modeling, as well as epifluorescence and stimulated emission depletion microscopy to investigate the role of DivIVA in Streptococcus pneumoniae cell morphogenesis. Our work reveals two distinct phases of peptidoglycan remodeling during the cell cycle that are differentially controlled by DivIVA. In particular, we show that DivIVA ensures homogeneous septum cleavage and peripheral peptidoglycan synthesis around the division site and their maintenance throughout the cell cycle. Our data additionally suggest that DivIVA impacts the contribution of the elongasome and class A penicillin-binding proteins to cell elongation. We also report the position of DivIVA on either side of the septum, consistent with its known affinity for negatively curved membranes. Finally, we take the opportunity provided by these new observations to propose hypotheses for the mechanism of action of this key morphogenetic protein.IMPORTANCEThis study sheds light on fundamental processes governing bacterial growth and division, using integrated click chemistry, advanced microscopy, and computational modeling approaches. It addresses cell wall synthesis mechanisms in the opportunistic human pathogen Streptococcus pneumoniae, responsible for a range of illnesses (otitis, pneumonia, meningitis, septicemia) and for one million deaths every year worldwide. This bacterium belongs to the morphological group of ovococci, which includes many streptococcal and enterococcal pathogens. In this study, we have dissected the function of DivIVA, which is a structural protein involved in cell division, morphogenesis, and chromosome partitioning in Gram-positive bacteria. This work unveils the role of DivIVA in the orchestration of cell division and elongation along the pneumococcal cell cycle. It not only enhances our understanding of how ovoid bacteria proliferate but also offers the opportunity to consider how DivIVA might serve as a scaffold and sensor for particular membrane regions, thereby participating in various cell cycle processes.

GhEXL3 participates in brassinosteroids regulation of fiber elongation in Gossypium hirsutum.

Cotton fiber (Gossypium hirsutum) serves as an ideal model for investigating the molecular mechanisms of plant cell elongation at the single-cell level. Brassinosteroids (BRs) play a crucial role in regulating plant growth and development. However, the mechanism by which BR influences cotton fiber elongation remains incompletely understood. In this study, we identified EXORDIUM-like (GhEXL3) through transcriptome analysis of fibers from BR-deficient cotton mutant pagoda 1 (pag1) and BRI1-EMS-SUPPRESSOR 1 (GhBES1.4, encoding a central transcription factor of BR signaling) overexpression cotton lines. Knockout of GhEXL3 using CRISPR/Cas9 was found to impede cotton fiber elongation, while its overexpression promoted fiber elongation, suggesting a positive regulatory function for GhEXL3 in fiber elongation. Furthermore, in vitro ovule culture experiments revealed that the overexpression of GhEXL3 partially counteracted the inhibitory effects of brassinazole (BRZ) on cotton fiber elongation, providing additional evidence of GhEXL3 involvement in BR signaling pathways. Moreover, our findings demonstrate that GhBES1.4 directly binds to the E-box (CACGTG) motif in the GhEXL3 promoter region and enhances its transcription. RNA-seq analysis revealed that overexpression of GhEXL3 upregulated the expression of EXPs, XTHs, and other genes associated with fiber cell elongation. Overall, our study contributes to understanding the mechanism by which BR regulates the elongation of cotton fibers through the direct modulation of GhEXL3 expression by GhBES1.4.

Organ-specific transcriptional regulation by HFR1 and HY5 in response to shade in Arabidopsis.

Light is crucial for plants and serves as a signal for modulating their growth. Under shade, where red to far-red light ratio is low, plants exhibit shade avoidance responses (SAR). LONG HYPOCOTYL IN FAR-RED 1 (HFR1) and ELONGATED HYPOCOTYL 5 (HY5) are known to be negative regulators of SAR and physically interact with one another. However, transcriptional regulatory network underlying SAR by these two transcription factors has not been explored. Here, we performed organ-specific transcriptome analyses of Arabidopsis thaliana hfr1-5, hy5-215 and hfr1hy5 to identify genes that are co-regulated by HFR1 and HY5 in hypocotyls and cotyledons. Genes co-regulated by HFR1 and HY5 were enriched in various processes related to cell wall modification and chlorophyll biosynthesis in hypocotyls. Phytohormone (abscisic acid and jasmonic acid) and light responses were significantly regulated by HFR1 and HY5 in both organs, though it is more prominent under shade in cotyledons. HFR1 and HY5 also differentially regulate the expression of the cell wall-related genes for xyloglucan endotransglucosylase/hydrolase, expansin, arabinogalactan protein and class III peroxidase depending on the organs. Furthermore, HFR1 and HY5 cooperatively regulated hypocotyl responsiveness to shade through auxin metabolism. Together, our study illustrates the importance of the HFR1-HY5 module in regulating organ-specific shade responses in Arabidopsis.

Ontogenetic differences in sun and shade galls of Clinodiplosis profusa on Eugenia uniflora leaves and the cytological antioxidant mechanisms in gall cells.

The gall-host Eugenia uniflora (Myrtaceae) is adaptable to different light conditions, enabling leaf production and survival in both sun and shade. Leaves of E. uniflora in shaded environments have more mesophyll layers, and galls of Clinodiplosis profusa (Cecidomyiidae) are larger and wider. Based on these previous observations, this study investigated the morphogenesis of galls induced by C. profusa on leaves of E. uniflora in different light conditions, revealing if the galls have a potential for acclimation, as observed with leaves. For this purpose, we compared the anatomical, histometric, and histochemical development of leaves and galls at different stages of development in sun and shade environments. Additionally, we analyzed the cytological features of the tissues composing the mature gall walls. Cells of shade galls expanded more toward the end of the developmental phase, which may explain the larger volume found for shade galls in a previous study. However, during the mature phase, these galls showed no significant differences in tissue thickness and final cell elongation in the contrasting light conditions. In the ultrastructural analyses, mature galls showed a gradient distinguishing the outer and inner parenchyma cells. The inner parenchyma had nutritive cells, with dense cytoplasm and abundant organelles. A higher accumulation of starch grains in nutritive cells, with evidence of hydrolysis of starch grains detected in the innermost layers leads to the accumulation of reducing sugars, which, with the presence of plastoglobules and protein bodies, are important mechanisms of oxidative stress dissipation in the cells in contact with the gall inducer.

Jasmonate signaling modulates root growth by suppressing iron accumulation during ammonium stress.

Plants adapt to changing environmental conditions by adjusting their growth physiology. Nitrate (NO3-) and ammonium (NH4+) are the major inorganic nitrogen forms for plant uptake. However, high NH4+ inhibits plant growth, and roots undergo striking changes, such as inhibition of cell expansion and division, leading to reduced root elongation. In this work, we show that high NH4+ modulates nitrogen metabolism and root developmental physiology by inhibiting iron (Fe)-dependent Jasmonate (JA) signaling and response in Arabidopsis (Arabidopsis thaliana). Transcriptomic data suggested that NH4+ availability regulates Fe and JA-responsive genes. High NH4+ levels led to enhanced root Fe accumulation, which impaired nitrogen balance and growth by suppressing JA biosynthesis and signaling response. Integrating pharmacological, physiological, and genetic experiments revealed the involvement of NH4+ and Fe-derived responses in regulating root growth and nitrogen metabolism through modulation of the JA pathway during NH4+ stress. The JA signaling transcription factor MYC2 directly bound the promoter of the NITRATE TRANSPORTER 1.1 (NRT1.1) and repressed it to optimize the NH4+/Fe-JA balance for plant adaptation during NH4+ stress. Our findings illustrate the intricate balance between nutrient and hormone-derived signaling pathways that appear essential for optimizing plant growth by adjusting physiological and metabolic responses during NH4+/Fe stress.

Exploring the puzzle of reactive oxygen species acting on root hair cells.

Reactive oxygen species (ROS) are essential signaling molecules that enable cells to respond rapidly to a range of stimuli. The ability of plants to recognize various stressors, incorporate a variety of environmental inputs, and initiate stress-response networks depends on ROS. Plants develop resilience and defensive systems as a result of these processes. Root hairs are central components of root biology since they increase the surface area of the root, anchor it in the soil, increase its ability to absorb water and nutrients, and foster interactions between microorganisms. In this review, we specifically focused on root hair cells and we highlighted the identification of ROS receptors, important new regulatory hubs that connect ROS production, transport, and signaling in the context of two hormonal pathways (auxin and ethylene) and under low temperature environmental input related to nutrients. As ROS play a crucial role in regulating cell elongation rates, root hairs are rapidly gaining traction as a very valuable single plant cell model for investigating ROS homeostasis and signaling. These promising findings might soon facilitate the development of plants and roots that are more resilient to environmental stressors.

Cotton BLH1 and KNOX6 antagonistically modulate fiber elongation via regulation of linolenic acid biosynthesis.

BEL1-LIKE HOMEODOMAIN (BLH) proteins are known to function in various plant developmental processes. However, the role of BLHs in regulating plant cell elongation is still unknown. Here, we identify a BLH gene, GhBLH1, that positively regulates fiber cell elongation. Combined transcriptomic and biochemical analyses reveal that GhBLH1 enhances linolenic acid accumulation to promote cotton fiber cell elongation by activating the transcription of GhFAD7A-1 via binding of the POX domain of GhBLH1 to the TGGA cis-element in the GhFAD7A-1 promoter. Knockout of GhFAD7A-1 in cotton significantly reduces fiber length, whereas overexpression of GhFAD7A-1 results in longer fibers. The K2 domain of GhKNOX6 directly interacts with the POX domain of GhBLH1 to form a functional heterodimer, which interferes with the transcriptional activation of GhFAD7A-1 via the POX domain of GhBLH1. Overexpression of GhKNOX6 leads to a significant reduction in cotton fiber length, whereas knockout of GhKNOX6 results in longer cotton fibers. An examination of the hybrid progeny of GhBLH1 and GhKNOX6 transgenic cotton lines provides evidence that GhKNOX6 negatively regulates GhBLH1-mediated cotton fiber elongation. Our results show that the interplay between GhBLH1 and GhKNOX6 modulates regulation of linolenic acid synthesis and thus contributes to plant cell elongation.

Auxin co-receptor IAA17/AXR3 controls cell elongation in Arabidopsis thaliana root solely by modulation of nuclear auxin pathway.

The nuclear TIR1/AFB-Aux/IAA auxin pathway plays a crucial role in regulating plant growth and development. Specifically, the IAA17/AXR3 protein participates in Arabidopsis thaliana root development, response to auxin and gravitropism. However, the mechanism by which AXR3 regulates cell elongation is not fully understood. We combined genetical and cell biological tools with transcriptomics and determination of auxin levels and employed live cell imaging and image analysis to address how the auxin response pathways influence the dynamics of root growth. We revealed that manipulations of the TIR1/AFB-Aux/IAA pathway rapidly modulate root cell elongation. While inducible overexpression of the AXR3-1 transcriptional inhibitor accelerated growth, overexpression of the dominant activator form of ARF5/MONOPTEROS inhibited growth. In parallel, AXR3-1 expression caused loss of auxin sensitivity, leading to transcriptional reprogramming, phytohormone signaling imbalance and increased levels of auxin. Furthermore, we demonstrated that AXR3-1 specifically perturbs nuclear auxin signaling, while the rapid auxin response remains functional. Our results shed light on the interplay between the nuclear and cytoplasmic auxin pathways in roots, revealing their partial independence but also the dominant role of the nuclear auxin pathway during the gravitropic response of Arabidopsis thaliana roots.

Gibberellic acid promotes single-celled fiber elongation through the activation of two signaling cascades in cotton.

The agricultural green revolution spectacularly enhanced crop yield through modification of gibberellin (GA) signaling. However, in cotton, the GA signaling cascades remain elusive, limiting our potential to cultivate new cotton varieties and improve yield and quality. Here, we identified that GA prominently stimulated fiber elongation through the degradation of DELLA protein GhSLR1, thereby disabling GhSLR1's physical interaction with two transcription factors, GhZFP8 and GhBLH1. Subsequently, the resultant free GhBLH1 binds to GhKCS12 promoter and activates its expression to enhance VLCFAs biosynthesis. With a similar mechanism, the free GhZFP8 binds to GhSDCP1 promoter and activates its expression. As a result, GhSDCP1 upregulates the expression of GhPIF3 gene associated with plant cell elongation. Ultimately, the two parallel signaling cascades synergistically promote cotton fiber elongation. Our findings outline the mechanistic framework that translates the GA signal into fiber cell elongation, thereby offering a roadmap to improve cotton fiber quality and yield.

Glutaredoxin regulation of primary root growth is associated with early drought stress tolerance in pearl millet.

Seedling root traits impact plant establishment under challenging environments. Pearl millet is one of the most heat and drought tolerant cereal crops that provides a vital food source across the sub-Saharan Sahel region. Pearl millet's early root system features a single fast-growing primary root which we hypothesize is an adaptation to the Sahelian climate. Using crop modeling, we demonstrate that early drought stress is an important constraint in agrosystems in the Sahel where pearl millet was domesticated. Furthermore, we show that increased pearl millet primary root growth is correlated with increased early water stress tolerance in field conditions. Genetics including genome-wide association study and quantitative trait loci (QTL) approaches identify genomic regions controlling this key root trait. Combining gene expression data, re-sequencing and re-annotation of one of these genomic regions identified a glutaredoxin-encoding gene PgGRXC9 as the candidate stress resilience root growth regulator. Functional characterization of its closest Arabidopsis homolog AtROXY19 revealed a novel role for this glutaredoxin (GRX) gene clade in regulating cell elongation. In summary, our study suggests a conserved function for GRX genes in conferring root cell elongation and enhancing resilience of pearl millet to its Sahelian environment.

Pearl millet is a staple food for over 90 million people living in regions of Africa and India that typically experience high temperatures and little rainfall. It was domesticated about 4,500 years ago in the Sahel region of West Africa and is one of the most heat and drought tolerant cereal crops worldwide. In most plants, organs known as roots absorb water and essential nutrients from the soil. Young pearl millet plants develop a fast-growing primary root, but it is unclear how this unique feature helps the crop to grow in hot and dry conditions. Using weather data collected from the Sahel over a 20-year period, Fuente, Grondin et al. predicted by modelling that early drought stress is the major factor limiting pearl millet growth and yield in this region. Field experiments found that plants with primary roots that grow faster within soil were better at tolerating early drought than those with slower growing roots. Further work using genetic approaches revealed that a gene known as PgGRXC9 promotes the growth of the primary root. To better understand how this gene works, the team examined a very similar gene in a well-studied model plant known as Arabidopsis. This suggested that PgGRXC9 helps the primary root to grow by stimulating cell elongation within the root. Since it is well adapted to dry conditions, pearl millet is expected to play an important role in helping agriculture adjust to climate change. The findings of Fuente, Grondin et al. may be used by plant breeders to create more resilient and productive varieties of pearl millet.

The role of CEACAMs versus integrins in Helicobacter pylori CagA translocation: a systematic review.

The delivery of Helicobacter pylori CagA into host cells was long believed to occur through the integrin cell surface receptors. However, the role of CEACAM receptors has recently been highlighted, instead. Here, we have categorized the existing experimental evidence according to whether deletion, upregulation, downregulation, or inhibition of the target ligands (T4SS or HopQ) or receptors (integrins or CEACAMs), result in alterations in CagA phosphorylation, cell elongation, or IL-8 production. According to our analysis, the statistics favor the essence of most of the T4SS constituents and the involvement of HopQ adhesin in all three functions. Concerning the integrin family, the collected data is controversial, but yielding towards it being dispensable or involved in CagA translocation. Yet, regarding cell elongation, more events are showing ß1 integrin being involved, than αvß4 being inhibitory. Concerning IL-8 secretion, again there are more events showing α5, ß1 and ß6 integrins to be involved, than those showing inhibitory roles for ß1, ß4 and ß6 integrins. Finally, CEACAM 1, 3, and 5 are identified as mostly essential or involved in CagA phosphorylation, whereasCEACAM 4, 7, and 8 are found dispensable and CEACAM6 is under debate. Conversely, CEACAM1, 5 and 6 appear mostly dispensable for cell elongation. Noteworthy is the choice of cell type, bacterial strain, multiplicity and duration of infection, as well as the sensitivity of the detection methods, all of which can affect the variably obtained results.

Ethylene and ROS mediate root growth inhibition induced by the endocrine disruptor bisphenol A (BPA).

Bisphenol A (BPA) functions as a detrimental substance that disrupts the endocrine system in animals while also impeding the growth and development of plants. In our previous study, we demonstrated that BPA hinders the growth of roots in Arabidopsis by diminishing cell division and elongation, which is ascribed to the increased accumulation and redistribution of auxin. Here, we examined the mediation of ROS and ethylene in BPA-induced auxin accumulation and root growth inhibition. BPA enhanced ROS levels, and ROS increased auxin contents but reduced cell division activity and the expression of EXPA8 involved in root elongation. ROS scavenger treatment reversed BPA-triggered root growth retardation, auxin accumulation, and cell division inhibition. In addition, BPA induced ethylene, and ethylene synthesis inhibitor treatment reversed BPA-triggered root growth retardation and auxin accumulation. Taken together, ROS and ethylene are involved in BPA-inhibited cell elongation and cell division by mediating auxin accumulation and redistribution.

In-Depth Quantification of Cell Division and Elongation Dynamics at the Tip of Growing Arabidopsis Roots Using 4D Microscopy, AI-Assisted Image Processing and Data Sonification.

One of the fundamental questions in plant developmental biology is how cell proliferation and cell expansion coordinately determine organ growth and morphology. An amenable system to address this question is the Arabidopsis root tip, where cell proliferation and elongation occur in spatially separated domains, and cell morphologies can easily be observed using a confocal microscope. While past studies revealed numerous elements of root growth regulation including gene regulatory networks, hormone transport and signaling, cell mechanics and environmental perception, how cells divide and elongate under possible constraints from cell lineages and neighboring cell files has not been analyzed quantitatively. This is mainly due to the technical difficulties in capturing cell division and elongation dynamics at the tip of growing roots, as well as an extremely labor-intensive task of tracing the lineages of frequently dividing cells. Here, we developed a motion-tracking confocal microscope and an Artificial Intelligence (AI)-assisted image-processing pipeline that enables semi-automated quantification of cell division and elongation dynamics at the tip of vertically growing Arabidopsis roots. We also implemented a data sonification tool that facilitates human recognition of cell division synchrony. Using these tools, we revealed previously unnoted lineage-constrained dynamics of cell division and elongation, and their contribution to the root zonation boundaries.

Ethylene response factor ERF022 is involved in regulating Arabidopsis root growth.

Ethylene response factors (ERFs) are involved in the regulation of plant development processes and stress responses. In this study, we provide evidence for the role of ERF022, a member of the ERF transcription factor group III, in regulating Arabidopsis root growth. We found that ERF022-loss-of-function mutants exhibited increased primary root length and lateral root numbers, and also morphological growth advantages compared to wild-type. Further studies showed that mutants had enhanced cell size in length in the root elongation zones. These results were accompanied by significant increase in the expression of cell elongation and cell wall expansion related genes SAUR10, GASA14, LRX2, XTH19 in mutants. Moreover, ERF022-mediated root growth was associated with the enhanced endogenous auxin and gibberellins levels. Our results suggest that loss-of-function of ERF022 up-regulated the expression of cell elongation and cell wall related genes through auxin and gibberellins signal in the regulation of root growth. Unexpectedly, ERF022 overexpression lines also showed longer primary roots and more lateral roots compared to wild-type, and had longer root apical meristematic zone with increased cell numbers. Overexpression of ERF022 significantly up-regulated cell proliferation, organ growth and auxin biosynthesis genes EXO, HB2, GALK2, LBD26, YUC5, which contribute to enhanced root growth. Altogether, our results provide genetic evidence that ERF022 plays an important role in regulating root growth in Arabidopsis thaliana.