Biology subjects

Kang, B. H.

Publications and source records attributed to Kang, B. H..

7 recordsLinked to original sources

bioRxiv2025

Root Cap-Specific Transcriptomics Identify the NAC Transcription Factor SOMBRERO as a Versatile Regulator of Auxin Gradients

Auxin gradients in the root cap play a crucial role in the root cap development and root tropism. In the central root cap, meristematic cells in the columella initial differentiate into gravity-sensing columella cell, and mature into border-like cells that eventually separate from the root cap. Golgi stacks exhibit distinct ultrastructural features in each cell type across the central root cap, serving as effective cell markers. This cell type-specific Golgi remodeling was inhibited in smb-3 mutant root cap. When we carried out transcriptomic analyses of isolated root cap from Col-0 and smb-3, transcript levels of numerous auxin-related genes, including those involved in auxin synthesis, transport, and signaling, were significantly altered in smb-3 mutant root caps. The auxin gradient was suppressed within the central root cap of smb-3 mutant lines and they displayed decreased sensitivity to N-1-naphthylphthalamic acid (NPA) in comparison to Col-0. Furthermore, we demonstrated that the SMB binds to the promoter regions of auxin-related genes displaying large changes in smb-3 root cap cells. Our findings suggest that SMB functions as a versatile transcription factor that regulates the expression of genes critical for local auxin distribution and responses in the root cap, thereby coordinating root cap cell differentiation and controlling root growth directions in response to external stimuli.

plant biology↗

bioRxiv2024

Gut microbiota dysbiosis induced by brain tumor modulates the efficacy of immunotherapy

BackgroundAlthough the influence of gut microbiota on various tumors has gained recognition, the intricate mechanisms underlying their effects on brain tumors remain largely unexplored. In this study, our objective was to unveil pivotal gut microbiota that contribute significantly to the anti-tumor immune response against brain tumors. ResultsDuring the progression of brain tumors, our research uncovered a notable shift in the gut microbiome, as revealed through comprehensive 16S rRNA sequencing analysis. This shift coincided with a substantial decrease in the concentration of tryptophan in fecal samples, indicating a potential link between tryptophan levels and microbiome composition. Intriguingly, dietary supplementation with tryptophan significantly mitigated these microbial alterations, suggesting a restorative effect on the gut microbiota composition. This intervention not only reversed the changes observed in the gut microbiome but also markedly improved survival rates, a phenomenon that was determined to be dependent on the gut microbiota. The mechanism underlying this improvement appears to involve an enhancement in T cell circulation, which in turn boosts the efficacy of immunotherapeutic approaches. Upon further investigation into the specific microbial species that were positively influenced by tryptophan supplementation, some candidates were screened. Among several gut microbiota strains restored by tryptophan supplementation, the most significant is Duncaniella dubosii. Through sole colonization into germ-free mice, we found that the presence of Duncaniella dubosii alone was able to replicate the beneficial effects observed with tryptophan supplementation. ConclusionsThis study highlights Duncaniella dubosiis crucial role in linking tryptophan supplementation to positive shifts in the gut microbiome, immune modulation, and enhanced survival during brain tumor progression. It underscores the complex interaction between diet, microbiota, and immune responses, offering novel insights for boosting cancer immunotherapys success.

microbiology↗

bioRxiv2023

Bearskin2 mediates the coordinated secretion of xylogalacturonan and root cap polygalacturonase in Arabidopsis border-like cells

Border-like cells (BLCs) are sheets of cells that are continuously sloughed off and replenished at the Arabidopsis root cap surface. ROOT CAP POLYGALACTURONASE (RCPG) encodes a putative pectinase involved in BLC shedding. Xylogalacturonan (XGA) is a pectic polysaccharide whose synthesis is associated with cell detachment and secreted separately from other cell wall polysaccharides. BEARSKIN1 (BRN1) and BRN2 are Arabidopsis NAC family transcription factors, and RCPG expression is inhibited in brn1/2. To explore the link between XGA and RCPG, we examined XGA synthesis in Arabidopsis lines with altered RCPG levels. We found that RCPG was contained in XGA-carrying vesicles budding from the trans-Golgi, but XGA synthesis was not affected in the rcpg mutant. XGA was absent in BLCs of brn2, but not of brn1, indicating that BRN2 is necessary for XGA synthesis. Overexpression of functional RCPG-GFP (oeRCPG-GFP) caused upregulation of BRN2, ectopic XGA synthesis, overaccumulation of endogenous RCPG, and accelerated BLC turnover, suggesting a positive regulatory loop between RCPG and BRN2. Inactivation of BRN2 in oeRCPG-GFP suppressed RCPG-GFP expression, excess RCPG, and XGA synthesis. Our data provide evidence that XGA and RCPG are secreted together and that BRN2 controls XGA synthesis, which facilitates RCPG export and BLC separation.

cell biology↗

bioRxiv2022

Unusual Morphological Changes of Rugositalea oryzae, A Novel Wrinkled Bacterium Isolated from The Rice Rhizosphere, Under Nutrient Stress

Bacterial cell morphology might result from natural selection to gain a competitive advantage under environmentally stressful conditions such as nutrient limitation. A bacterial strain YC6860T isolated from the rhizosphere of rice (Oryza sativa L.) showed pleomorphic behavior with smooth cell morphology and wrinkled surface rods depending upon nutritional conditions. Based on scanning and transmission electron microscopy studies, we hypothesized that the surface-to-volume ratio of cells increases with decreasing nutrient concentrations. The transition from smooth to wrinkled cell surface morphology could be one of the adaptation strategies by which YC6860T maximizes its ability to access available nutrients. To characterize the properties of the wrinkled strain, we performed taxonomic and phylogenetic analyses. 16S rRNA gene sequencing results showed that the strain represented a novel, deep-rooting lineage within the order Rhizobiales with the highest similarity of 94.2% to Pseudorhodoplanes sinuspersici RIPI 110T. Whole genome sequencing was also performed to characterize its genetic features. The strain YC6860T might belong to a new genus, named Rugositalea, and a new species, named Rugositalea oryzae, In addition, taxonomic analysis showed that YC6860T is Gram-negative, aerobic, and rod-shaped with large regular wrinkles resembling a delicate twist of fusilli, measuring 0.5-0.6 {micro}m in width and 1.5-1.6 {micro}m in length under nutrient-limiting conditions. This unique cell structure with regular rugosity could be the first finding that has not been reported in the existing bacterial morphology.

microbiology↗

bioRxiv2022

Identification of highly cross-reactive mimotopes for a public T cell response in murine melanoma

While immune checkpoint blockade results in durable responses for some patients, many others have not experienced such benefits. These treatments rely upon reinvigorating specific T cell-antigen interactions. However, it is often unknown what antigens are being recognized by T cells or how to potently induce antigen-specific responses in a broadly applicable manner. Here, we characterized the CD8+ T cell response to a murine model of melanoma following combination immunotherapy to determine the basis of tumor recognition. Sequencing of tumor-infiltrating T cells revealed a repertoire of highly homologous TCR sequences that were particularly expanded in treated mice and which recognized an antigen from an endogenous retrovirus. While vaccination against this peptide failed to raise a protective T cell response in vivo, engineered antigen mimotopes induced a significant expansion of CD8+ T cells cross-reactive to the original antigen. Vaccination with mimotopes resulted in killing of antigen-loaded cells in vivo yet showed modest survival benefit in a prophylactic vaccine paradigm. Together, this work demonstrates the identification of a dominant tumor-associated antigen and generation of mimotopes which can induce robust functional T cell responses that are cross-reactive to the endogenous antigen across multiple individuals.

immunology↗

bioRxiv2022

Autophagy promotes organelle clearance and organized cell separation of living root cap cells in Arabidopsis thaliana

The root cap is a multi-layered tissue covering the tip of a plant root that directs root growth through its unique functions such as gravity-sensing and rhizosphere interaction. To prevent damages from the soil environment, cells in the root cap continuously turn over through balanced cell division and cell detachment at the inner and the outer cell layers, respectively. Upon displacement toward the outermost layer, columella cells at the central root cap domain functionally transition from gravity-sensing cells to secretory cells, but the mechanisms underlying this drastic cell fate transition are largely unknown. By using live-cell tracking microscopy, we here show that organelles in the outermost cell layer undergo dramatic rearrangements, and at least a part of this rearrangement depends on spatiotemporally regulated activation of autophagy. Notably, this root cap autophagy does not lead to immediate cell death, but rather is necessary for organized separation of living root cap cells, highlighting a previously undescribed role of developmentally regulated autophagy in plants. Summary statementTime-lapse microscope imaging revealed spatiotemporal dynamics of intracellular reorganization associated with functional transition and cell separation in the Arabidopsis root cap and the roles of autophagy in this process.

plant biology↗

bioRxiv2020

Changes in the plasmodesma structure and permeability at the bundle sheath and mesophyll interface during the maize C4 leaf development

Plasmodesmata are intercellular channels that facilitate molecular diffusion between neighboring plant cells. The development and functions of plasmodesmata are controlled by multiple intra- and intercellular signaling pathways. Plasmodesmata are critical for dual-cell C4 photosynthesis in maize because plasmodesmata at the mesophyll and bundle sheath interface mediate exchange of CO2-carrying organic acids. We examined developmental profiles of plasmodesmata and chloroplasts in the maize leaf from young cells in the base to mature cell in the tip using microscopy approaches. Young mesophyll and bundle sheath cells in the leaf base had proplastids, and their plasmodesmata were simple, devoid of cytoplasmic sleeves. In maturing cells where Kranz anatomy and dimorphic chloroplasts were evident, we observed extensive remodeling of plasmodesmata that included acquisition of an electron-dense ring on the mesophyll side and cytoplasmic sleeves on the bundle sheath side. Interestingly, the changes in plasmodesmata involved a drop in symplastic dye mobility and suberin accumulation in the cell wall, implying a more stringent mesophyll-bundle sheath transport. We compared kinetics of the plasmodesmata and the cell wall modification in wildtype leaves with leaves from ppdk and dct2 mutants with defective C4 pathways. Plasmodesmata development, symplastic transport inhibition, and cell wall suberization were accelerated in the mutant lines, probably due to the aberrant C4 cycle. Transcriptomic analyses of the mutants confirmed the expedited changes in the cell wall. Our results suggest that a regulatory machinery at the mesophyll-bundle sheath boundary suppresses erroneous flux of C4 metabolites in the maize leaf. Significance StatementPlasmodesmata in the maize Kranz anatomy mediate the exchange of organic acids between mesophyll and bundle sheath. Since solute diffusion through plasmodesmata is governed by solute concentration gradients, a balanced distribution of C4 metabolites is critical for concentration of CO2 in the bundle sheath. Plasmodesmata bridging the mesophyll and bundle sheath cytoplasm have a cylindrical cavity, which can facilitate molecular movements, and a valve-like attachment. Construction of the sophisticated plasmodesmata was linked to C4 photosynthesis, and plasmodesmata assembly finished more rapidly in maize mutants with defective C4 pathways than in wild-type plants. These results suggest that the specialized plasmodesmata contribute to controlled transport of C4 metabolites.

plant biology↗