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| 2. |
- Chen, J. Y., et al.
(författare)
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High-resolution 3D imaging uncovers organ-specific vascular control of tissue aging
- 2021
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:6
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Tidskriftsartikel (refereegranskat)abstract
- Blood vessels provide supportive microenvironments for maintaining tissue functions. Age-associated vascular changes and their relation to tissue aging and pathology are poorly understood. Here, we perform 3D imaging of young and aging vascular beds. Multiple organs in mice and humans demonstrate an age-dependent decline in vessel density and pericyte numbers, while highly remodeling tissues such as skin preserve the vasculature. Vascular attrition precedes the appearance of cellular hallmarks of aging such as senescence. Endothelial VEGFR2 loss-of-function mice demonstrate that vascular perturbations are sufficient to stimulate cellular changes coupled with aging. Age-associated tissue-specific molecular changes in the endothelium drive vascular loss and dictate pericyte to fibroblast differentiation. Lineage tracing of perivascular cells with inducible PDGERB and NG2 Cre mouse lines demonstrated that increased pericyte to fibroblast differentiation distinguishes injury-induced organ fibrosis and zymosan-induced arthritis. To spur further discoveries, we provide a freely available resource with 3D vascular and tissue maps.
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| 3. |
- Sivan, Pramod, 1984-, et al.
(författare)
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Anatomy and cell wall chemistry of tension wood in Hibiscus cannabinus
- 2021
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Ingår i: Bosque (Valdivia). - : SciELO Agencia Nacional de Investigacion y Desarrollo (ANID). - 0304-8799 .- 0717-9200. ; 42:1, s. 99-110
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Tidskriftsartikel (refereegranskat)abstract
- Hibiscus cannabinus (kenaf) is well known as a source for textile fibers and as an alternate source for cellulosic fibers for paper and pulp industry. Formation of reaction xylem alters the chemical properties of fibers, which may affect its uses. To the best of our knowledge, there are no reports on the occurrence of reaction xylem in kenaf. The present study examines reaction xylem (i.e. tension wood and its opposite side) formed in response to bending of stems in Kenaf by anatomical, histochemical and biochemical methods. The reaction xylem found on the upper side of leaning stems showed an eccentric growth pattern, thin walls, shorter and wider fibers without gelatinous layer, decrease of vessel or ray density as compared to wood formed on opposite sides. Histochemical localization of lignin using Weisner reaction and Maule’s test indicated presence of more syringyl units in the fiber wall of tension wood. Gravimetric quantification of cell wall polymers showed relatively more amount of holocellulose and hemicellulose in tension wood (69 and 46 %, respectively) compared to those of opposite wood (63 and 42 %, respectively). There was no significant difference noticed in the klason lignin content between opposite (17.4 %) and tension wood (16.7 %). Lignin characterization by the thioacidolysis method revealed that the tension wood lignin in kenaf was composed of more amount of syringyl and p-hydroxyphenyl monomers compared to that of opposite side wood. This analysis also suggests that the tension wood lignin is rich in β-aryl ether linkages in syringyl units resulting in high S/G ratio.
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| 4. |
- Sivan, Pramod, 1984-, et al.
(författare)
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Chemical Composition in Juvenile and Mature Wood of Branch and Main Trunk of Leucaena leucocephala (Lam.) de Wit
- 2023
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Ingår i: PLANTS. - : MDPI AG. - 2223-7747. ; 12:23
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Tidskriftsartikel (refereegranskat)abstract
- Secondary growth is the most dynamic developmental aspect during the terrestrialization of plants. The development of secondary xylem tissue composed of thick-walled cells with characteristic changes in its structure and chemistry facilitates the growth and development of woody plants. In the present study, the chemical composition of the secondary xylem of juvenile and mature wood from the branch and main trunk of Leucaena leucocephala, has been investigated and the differences established. The biochemical analysis of different cell wall components in the mature wood of the main trunk revealed high holocellulose and α-cellulose and less lignin content in the juvenile wood while its syringyl/guaiacyl (S/G) ratio was less than for the mature wood. As compared to the branch xylem, concentration of cell wall polysaccharides and lignin content was higher in both juvenile and mature wood collected from the main trunk. Thioacidolysis and GC-MS analysis of wood lignin from juvenile and mature wood showed that an increased concentration in lignin content in mature wood is associated with a corresponding increase in S/G ratio. The structural information of the acetylated lignin was investigated by 1H NMR spectroscopy. Our results indicate that the mature wood from the main trunk is superior in pulp yielding and lignin degradability as compared to the juvenile wood of the branch and trunk.
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| 5. |
- Sivan, Pramod, 1984-, et al.
(författare)
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Dieback of Gmelina arborea Trees and Structural Alterations Induced in the Wood Cell Walls by Alternaria alternata
- 2022
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Ingår i: FORESTIST. - : AVES YAYINCILIK A.Ş.. - 2602-4039. ; 72:1, s. 2-9
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Tidskriftsartikel (refereegranskat)abstract
- The death and structural alterations in the secondary xylem of Gmelina arborea trees in response to fungal invasion were investigated by light and electron microscopy methods. In vivo experiments indicate that Alternaria alternata is an aggressive pathogen which invades the deeper part of the wood in the branches-up to 4 cm from the site of infection--within 10 days of inoculation. The mycelial invasion occurred through pits and boreholes formed by the fungus in the vessels, fibers, and axial and ray parenchyma cells. Scanning electron microscopy also revealed the colonization of fungus through pit and vessel elements. In vitro studies showed that ray cells and fibers were more prone to cell wall damage in contrast to vessels during the initial stage of infection. The etiology of infection found in the infected samples collected from the living trees and samples of in vivo and in vitro experiments showed similar patterns of infection and confirmed that A. alternata is responsible for the mortality and decay in Gmelina trees. It causes a typical soft-rot pattern with cell wall alterations such as cavity formation by "L" bending. The separation of fibers at the compound middle lamella region indicated that the fungus is capable of degrading both lignin-rich regions of cell walls. The boreholes in the fiber wall also showed distinct variations in size and shape. The penetration of fungal hyphae through the middle lamella and removal of lignin from the cell walls was also confirmed with transmission electron microscopy studies.
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| 7. |
- Karumanchi, Appa Rao, et al.
(författare)
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Root and Leaf Anatomy, Ion Accumulation, and Transcriptome Pattern under Salt Stress Conditions in Contrasting Genotypes of Sorghum bicolor
- 2023
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Ingår i: PLANTS. - : MDPI AG. - 2223-7747. ; 12:13
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Tidskriftsartikel (refereegranskat)abstract
- Roots from salt-susceptible ICSR-56 (SS) sorghum plants display metaxylem elements with thin cell walls and large diameter. On the other hand, roots with thick, lignified cell walls in the hypodermis and endodermis were noticed in salt-tolerant CSV-15 (ST) sorghum plants. The secondary wall thickness and number of lignified cells in the hypodermis have increased with the treatment of sodium chloride stress to the plants (STN). Lignin distribution in the secondary cell wall of sclerenchymatous cells beneath the lower epidermis was higher in ST leaves compared to the SS genotype. Casparian thickenings with homogenous lignin distribution were observed in STN roots, but inhomogeneous distribution was evident in SS seedlings treated with sodium chloride (SSN). Higher accumulation of K+ and lower Na+ levels were noticed in ST compared to the SS genotype. To identify the differentially expressed genes among SS and ST genotypes, transcriptomic analysis was carried out. Both the genotypes were exposed to 200 mM sodium chloride stress for 24 h and used for analysis. We obtained 70 and 162 differentially expressed genes (DEGs) exclusive to SS and SSN and 112 and 26 DEGs exclusive to ST and STN, respectively. Kyoto Encyclopaedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analysis unlocked the changes in metabolic pathways in response to salt stress. qRT-PCR was performed to validate 20 DEGs in each SSN and STN sample, which confirms the transcriptomic results. These results surmise that anatomical changes and higher K+/Na+ ratios are essential for mitigating salt stress in sorghum apart from the genes that are differentially up- and downregulated in contrasting genotypes.
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| 8. |
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| 9. |
- Sivan, Pramod, 1984-, et al.
(författare)
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Effect of Exogenously Applied 24-Epibrassinolide and Brassinazole on Xylogenesis and Microdistribution of Cell Wall Polymers in Leucaena leucocephala (Lam) De Wit
- 2021
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Ingår i: Journal of Plant Growth Regulation. - : Springer Nature. - 0721-7595 .- 1435-8107. ; 41:1, s. 404-416
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Tidskriftsartikel (refereegranskat)abstract
- Plant growth regulators play a key role in cell wall structure and chemistry of woody plants. Understanding of these regulatory signals is important in advanced research on wood quality improvement in trees. The present study is aimed to investigate the influence of exogenous application of 24-epibrassinolide (EBR) and brassinosteroid inhibitor, brassinazole (BRZ) on wood formation and spatial distribution of cell wall polymers in the xylem tissue of Leucaena leucocephala using light and immuno electron microscopy methods. Brassinazole caused a decrease in cambial activity, xylem differentiation, length and width of fibres, vessel element width and radial extent of xylem suggesting brassinosteroid inhibition has a concomitant impact on cell elongation, expansion and secondary wall deposition. Histochemical studies of 24-epibrassinolide treated plants showed an increase in syringyl lignin content in the xylem cell walls. Fluorescence microscopy and transmission electron microscopy studies revealed the inhomogenous pattern of lignin distribution in the cell corners and middle lamellae region of BRZ treated plants. Immunolocalization studies using LM10 and LM 11 antibodies have shown a drastic change in the micro-distribution pattern of less substituted and highly substituted xylans in the xylem fibres of plants treated with EBR and BRZ. In conclusion, present study demonstrates an important role of brassinosteroid in plant development through regulating xylogenesis and cell wall chemistry in higher plants.
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| 10. |
- Sivan, Pramod, 1984-, et al.
(författare)
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Post infectional alterations caused by Xylaria polymorpha in the secondary xylem of Lannea coromandelica (Houtt.) Merr
- 2021
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Ingår i: Forestist. - : AVES YAYINCILIK A.Ş.. - 2602-4039. ; 71:2, s. 93-101
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Tidskriftsartikel (refereegranskat)abstract
- Xylaria polymorpha is known to cause root rot disease in hardwood trees. In the present study, trees of the species Lannea coromandelica infected with X. polymorpha showed symptoms consistent with root rot disease and also presented with a soft rot decay pattern. Bright-field microscopy, Confocal Microscopy, and Scanning Electron Microscopy revealed that fungal mycelia penetrated the S2 layer of the fiber wall while axial parenchyma was found to be relatively resistant without much visible damage. Occasionally, separation of the parenchyma adjacent to fiber occurred due to the dissolution of the compound middle lamella. Ray parenchyma cells showed several boreholes having irregular shapes and sizes. Enlargement of the pits in axial and ray parenchyma was present in all the samples investigated. Xylem fibers were the most susceptible cell type and developed several tunnels through the S2 layer. Tunnels formed in the S2 layer of the fiber wall by the mycelia showed L- and/or T-bending. The diameter of the tunnels started narrow, increasing in size as the tunnels extended into the S3 layer. In some instances, complete removal of the S3 layer and fusion of the tunnels with the fiber lumen appearing as U-shaped erosion troughs was observed. At the advanced stage of decay, extensive damage was observed in the vessel walls, leaving the middle lamella and wall layer facing the vessel lumen intact. In conclusion the anatomical characteristics observed in the present study suggests that X. polymopha is an aggressive saprobe with strong ligninolytic activity causing soft rot type 2 decay in the wood cell wall of Lannea coromandelica.
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