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At least 19 recordsLinked to original sources
PubMed2026

Host genetic regulation of xylem-resident Pseudomonas enhances cucumber growth.

BACKGROUND: Although endophytic microorganisms play a critical role in plant growth and stress resilience, the genetic basis underlying host selection of beneficial microbiota-particularly within the xylem-remains poorly understood. Cucumber (Cucumis sativus), as a crop model with a well-developed system for studying vascular biology, offers a valuable system to investigate the host genetic determinants of xylem microbiome assembly. RESULTS: By conducting population-level microbiome profiling across 109 cucumber accessions, we identified a conserved xylem microbiota dominated by Proteobacteria. Within this community, 20 core amplicon sequence variants (ASVs) were consistently present in xylem sap. Genome-wide association mapping identified a host genetic locus, CsXPR1, which encodes a tetratricopeptide repeat protein that regulates the abundance of the dominant xylem-colonized Pseudomonas ASV_4. Colonization patterns of ASV_4 varied across host genotypes and were correlated with CsXPR1 expression levels, suggesting a precision genetic regulation of bacterial entry into vascular tissues. Pseudomonas fulva strain 220, with 97% 16S rRNA gene identity with ASV_4, could colonize in cucumber xylem by inoculation of either roots or leaves. Genome analysis and plate assays revealed the biosynthesis of indole-3-acetic acid (IAA), solubilization of phosphate, and a range of plant beneficial traits in strain 220. Inoculation with strain 220 significantly enhanced growth in cucumber, but only in CsXPR1 haplotype that exhibited high gene expression and higher recruitment capacity of the strain. These benefits included notable increases in plant height (38%), stem diameter (36%), leaf area (61%), fresh and dry weight (51% and 85%, respectively), and a 4.57-fold increase in 4-methyleneglutamine content within the xylem sap. CONCLUSION: Our findings reveal a complete "gene-to-function" pathway where the host gene CsXPR1 mediates a genotype-dependent growth promotion. It achieves this by regulating the xylem colonization of a beneficial bacterium, Pseudomonas fulva, which in turn enhances plant growth by enriching the xylem sap with the key metabolite 4-methyleneglutamine. Video Abstract.

Cucumis sativus↗
PubMed1970

Separation and identification of soluble nucleotides in cambial and young xylem tissue of Larix decidua Mill.

The nucleotides present in the cambial tissue (primary wall tissue) and in the not yet fully differentiated secondary xylem (secondary wall tissue) of Larix decidua Mill. were extracted and characterized. The method of extraction best suited to the material was investigated and the problems involved in desalting of extracts and their effect on the final nucleotide pattern obtained are discussed. UDP-glucose was found to be the most important sugar nucleotide isolated from both cambial and young xylem tissue. UDP-galactose, UDP-arabinose, UDP-xylose, UDP-fructose, GDP-glucose, GDP-galactose, GDP-mannose, ADP-glucose, ADP-galactose, ADP-fructose, ADP-ribose and ADP-ribose phosphate (the last two compounds are the acid breakdown products of NADH and NADPH respectively) were also found in both extracts. UDP-galacturonic acid was identified only in the extract of the primary wall material. Several nucleotide oligosaccharides were obtained from both the extract of cambial tissue and that of the young xylem.

Adenine Nucleotides↗
PubMed1977

Changes in enzymic activities of nucleoside diphosphate sugar interconversions during differentiation of cambium to xylem in sycamore and poplar.

During the transition from primary wall formation to secondary thickening there is a marked shift in the synthesis of pectin, hemicellulose and cellulose. The activities of the enzymes [UDP-D-galactose 4-epimerase (EC 5.1.3.2)8 UDP-l-arabinose 4-epimerase (EC 5.1.3.5), UDP-D-glucose dehydrogenase (EC 1.1.1.22) and UDP-D--glucuronate decarboxylase (EC 4.1.1.35)] were measured in cambial cells, differentiating xylem cells and differentiated xylem cells isolated from sycamore and poplar trees, and phloem cells from poplar. At the final stage of the differentiation of cambium to xylem there was a decrease in activity of the enzymes directly involved in producing the soluble precursors of pectin (DUP-D-galactose 4-epimerase and UDP-L-arabinose 4-epimerase and an increase in those producing the precursors of hemicellulose (UDP-D-glucose dehydrogenase and UDP-D-glucuronate decarboxylase). These results strongly suggest ahat the changes were correlated with the differences observed in the chemical composition of the wall during development. The changes found in the catalytic activity of the enzymes of nucleoside diphosphate sugar interconversion exert a coarse control over the synthesis of pectin and hemicelluloses. The tissues at all stages of development contained the necessary enzyme activities to produce all the precursors of pectin and hemicellulose, even at the final stage of differentiation when no pectin was formed.

Arabinose↗
PubMed1977

Changes in enzymic activities of nucleoside diphosphate sugar interconversions during differentiation of cambium to xylem in pine and fir.

A protein fraction [precipitate obtained between 40 and 65% (NH4)2SO4 satn.] prepared from cambial cells, differentiating xylem cells and differentiated xylem cells of pine and fir trees contained all the enzymes required for the nucleoside diphosphate sugar interconversions. By using UDP-D-[U-14C]glucose or UDP-D-[U-14C]galactose, UDP-D-[U-14C-]glucuronic acid and UDP-D-[U-14C]xylose as substrates, the activities of UDP-D-galactose 4-epimerase (DC 5.1.3.2), UDP-D-xylose 4-epimerase(EC 5.1.3.5), UDP-D-glucose dehydrogenase (EC 1.1.1.22) and UDP-D-glucuronate 4-epimerase (EC5.1.3.6), UDP-d-glucuronate decarboxylase (EC 4.1.1.35) were measured at different stages of cell-wall development. The specific activities and the activities per cell of these enzymes varied during differentiation of cambium to xylem according to the type polysaccharide synthesized. Variations were also found between the two species investigated. These data, compared with those obtained in out previous work on angiosperms [see the preceding paper, Dalessandro & Northcote (1977) Biochem. J. 162, 267-279], suggest that some control of polysaccharide synthesis operates at the level of the formation of the precursors of pectin and hemicellulose syntheses.

Carbohydrate Epimerases↗
PubMed1992

The graviosmotic hypothesis of xylem transport of water in plants.

This paper presents a full version of the graviosmotic hypothesis postulated earlier in outline (Kargol 1978), which concerns xylem rise of water in plants. According to this hypothesis water is transported by xylem vessels (at respective development stages of these vessels) using the graviosmotic mechanisms. A detailed description of hypothesis is introduced by a discussion of the development stages of xylem vessels and a presentation of graviosmotic mechanisms postulated to be involved. These mechanisms include: convective graviosmosis and related effects, gravidiffusional graviosmosis, and osmotic transport aided by gravitational force in multi-membrane systems. The presented hypothesis does not contradict the theory of transpiration-cohesion or that of root pressure; rather, it is complementary to them.

Biological Transport, Active↗
PubMed1974

Ultrastructural study of Pierce's disease bacterium in grape xylem tissue.

The rod-shaped rickettsia-like bacteria of Pierce's disease measure about 0.25 to 0.50 mum in diameter and 1.0 to 4.0 mum long. The bacteria have a cell wall consisting of a trilaminar outer membrane and two intermediate low-density layers separated by a dense intermediate layer. A trilaminar cytoplasmic membrane is also present, resulting in a total wall complex thickness of 25 to 40 nm. A periodic infolding of the outer membrane and intermediate layers of the wall give the wall surface a ridged apperance. The ridges appear to go around the long axis of the cell, possibly in the form of spirals. Ribosomes and nuclear regions with easily visible deoxyribonucleic acid strands and clumps are distributed throughout the cytoplasm. Binary fission, during which the cell wall and cytoplasmic membrane folded inward to partition the cell, was observed. In the xylem of infected grapes, the bacteria are either distributed evenly throughout the lumen of the xylem vessel or appressed along the inner surface of the vessel walls in an electron-lucent matrix.

Cell Membrane↗
PubMed1988

Staining of xylem parenchyma mitochondria with photo-oxidized 3,3'-diaminobenzidine.

A photo-oxidized solution of 3,3'-diaminobenzidine (DAB) is used to stain xylem parenchyma mitochondria in specimens prepared from lupin hypocotyls fixed with glutaraldehyde and osmium tetroxide and embedded in Epon. No other subcellular components, including plastids, nuclei, vacuoles or cell walls were stained when xylem parenchyma cells were exposed to this reagent for 1 hr. This reaction was stable for 20 min at 80 C, inhibited by KCN, and insensible to 3-amino-1,2,4-triazole. The outstanding sensitivity of this reaction to inhibition probes suggests that this stain is analogous to the previously described DAB/cytochrome c/cytochrome oxidase reaction in plant mitochondria, although the incubation of lupin sections with freshly prepared DAB solution (free of auto-oxidized DAB) did not result in staining. These results draw attention to the unreliability of DAB oxidation for demonstrating electron transport in plant mitochondria. However, we do recommend photo-oxidized DAB as a direct ultrastructural stain for plant mitochondria without reference to its oxidative capacity.

3,3'-Diaminobenzidine↗
PubMed1977

Comparison of vegetative anatomy of piperales. I. Juvenile xylem of twigs.

Medullary bundles of Piperaceae resemble those of Ranunculaceae. The nature of tracheary elements of primary xylem suggests that Houttuynia cordata (Saururaceae), Piper cubeba (Piperaceae) and Chloranthus officinalis (Chloranthaceae) are of lower evolutionary status than others. Among these three, P. cubeba shows stratification of secondary xylem, a specialized character. Lateral wall of metaxylem tracheary elements and distribution of bundles of Peperomia, suggest their primitive status and distinctness, supporting separation of "Peperomiacea:" (of NOVAK). Piper cubeba, Houttuynia and Chloranthus bear one important Ranunculaceous character: scalariform perforation in primary vessels. Primitive species of Peperomia carry probably another Ranunculaceous character, i.e., many circles of medullary bundles. Shape and pattern of vascular bundles of Piper cubeba, Houttuynia and Chloranthus are similar. Other species of Piper show modifications. Peperomia represents another distinct pattern.

Plants↗
PubMed1991

Seasonal changes in the concentration of the major storage protein and its mRNA in xylem ray cells of poplar trees.

In the autumn large amounts of a major storage protein accumulate in the woody stem of poplar trees. This protein is stored in xylem ray cells during the winter season and is degraded in late spring. The accumulation of this protein is preceded by a dramatic but transient appearance of the corresponding mRNA. Thus, the seasonal change in the mRNA content appears to be a crucial event for the storage of nitrogen in the stem. The amino acid sequence of the storage protein has been deduced from the nucleotide sequence of a full-length cDNA. The cDNA shows a nucleotide sequence similarity of approximately 75% with two published cDNA sequences of poplar which represent transcripts that accumulate systemically in leaves of poplar trees in response to wounding.

Amino Acid Sequence↗
PubMed1986

Identification of a new, naturally occurring, non proteic amino acid in xylem sap of Pisum sativum.

The xylem sap of nitrogen-fixing Pisum Sativum cv Homesteader has been examined by capillary gas chromatography and by gas chromatography mass spectrometry in both electron-impact and chemical ionization modes following the formation of N-heptafluorobutyryl isobutyl ester derivatives. One of the compounds thus detected had a mass of 389 and contained chlorine, one carboxylic acid group and a nitrogen atom. High-resolution mass spectrometry indicated that there were no other hetero atoms present in the molecule. The composition was determined to be C4H8NO2Cl. This composition can be explained only in terms of a chloroamino butyric acid.

Amino Acids↗
PubMed1975

An ultrastructural study of acid phosphatase localization in Phaseolus vulgaris xylem by the use of an azo-dye method.

The localization of acid phosphatase during xylem development has been examined in the bean, Phaseolus vulgaris. The azo dye, the final reaction product, is initially prominent in the dictyosomes, vesicles apparently participating in secondary wall formation, and in the middle lamella of the young vessel element. Final reaction particles are also present in mitochondria, chloroplasts, and certain vacuoles and are sparsely scattered in the cytoplasm. At a later stage of vessel differentiation, the azo dye is concentrated in the disintegrating cytoplasm and along the fibrils of the partially hydrolysed primary wall and middle lamella. In the mature vessel element, the azo dye is still present along the disintegrated primary wall at the side of the vessel and covers the secondary wall. In the parenchyma cell adjacent to the vessel element, acid phosphatase localization is found in the dictyosomes, endoplasmic reticulum, mitochondria, small vacuoles, and the middle lamella. The controls from all stages of vessel element development were free of azo dye particles. The concentration of acid phosphatase along the secondary walls of the mature vessels and in the middle lamella between other cells indicates that this enzyme has other functions besides autolysis of the cytoplasm and primary cell wall. Acid phosphatase may participate in the formation of the secondary wall and may also have a role in the secretion and transport of sugars.

Acid Phosphatase↗