Histological studies of ectomycorrhizae and root nodules from Cercocarpus montanus and Cercocarpus paucidentatus

The ectomycorrhizae of Cercocarpus montanus Raf. and Cercocarpus paucidentatus Britt. displayed morphologies ranging from single swollen short lateral roots on long roots to terminal pyramidal clusters. Most short roots appeared to be mycorrhizal, although C. paucidentatus was only infected under growth chamber conditions. Histological sections revealed a conspicuous fungal mantle, averaging 30 μ in thickness, and a Hartig's net.The root nodules appeared as swellings on lateral roots, and later formed compact coralloid orange-colored masses several centimeters in diameter. Histological analyses indicated that both species of Cercocarpus harbored a similar endophyte. Three developmental stages were noted in cortical tissue, including (a) hyphal masses in apical nodule cells; (b) hyphae terminating in 3 × 4 μ club-shaped vesicular swellings; and (c) older structureless hyphal masses in cells of mature nodule branches. The older hyphal masses did not appear to be absorbed by the host plant. The endophyte possessed branching filaments 0.5 μ in diameter and was considered to be an actinomycete.

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Metabolite Profiles of Nodulated Alfalfa Plants Indicate That Distinct Stages of Nodule Organogenesis Are Accompanied by Global Physiological Adaptations

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-19-0998 ◽

2006 ◽

Vol 19 (9) ◽

pp. 998-1013 ◽

Cited By ~ 36

Author(s):

Aiko Barsch ◽

Verena Tellström ◽

Thomas Patschkowski ◽

Helge Küster ◽

Karsten Niehaus

Keyword(s):

Organic Acid ◽

Host Plant ◽

Developmental Stages ◽

Root Nodules ◽

Nitrogen Deficiency ◽

Metabolic Changes ◽

Nodule Formation ◽

Control Mechanisms ◽

Symbiotic Interaction ◽

Metabolite Profiles

An effective symbiosis between Sinorhizobium meliloti and its host plant Medicago sativa is dependent on a balanced physiological interaction enabling the microsymbiont to fix atmospheric nitrogen. Maintenance of the symbiotic interaction is regulated by still poorly understood control mechanisms. A first step toward a better understanding of nodule metabolism was the determination of characteristic metabolites for alfalfa root nodules. Furthermore, nodules arrested at different developmental stages were analyzed in order to address metabolic changes induced during the progression of nodule formation. Metabolite profiles of bacteroid-free pseudonodule extracts indicated that early nodule developmental processes are accompanied by photosynthate translocation but no massive organic acid formation. To determine metabolic adaptations induced by the presence of nonfixing bacteroids, nodules induced by mutant S. meliloti strains lacking the nitrogenase protein were analyzed. The bacteroids are unable to provide ammonium to the host plant, which is metabolically reflected by reduced levels of characteristic amino acids involved in ammonium fixation. Elevated levels of starch and sugars in Fix¯ nodules provide strong evidence that plant sanctions preventing a transformation from a symbiotic to a potentially parasitic interaction are not strictly realized via photo-synthate supply. Instead, metabolic and gene expression data indicate that alfalfa plants react to nitrogen-fixation-deficient bacteroids with a decreased organic acid synthesis and an early induction of senescence. Noneffective symbiotic interactions resulting from plants nodulated by mutant rhizobia also are reflected in characteristic metabolic changes in leaves. These are typical for nitrogen deficiency, but also highlight metabolites potentially involved in sensing the N status.

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Early development of Rhizobium-induced root nodules of Parasponia rigida. II. Nodule morphogenesis and symbiotic development

Canadian Journal of Botany ◽

10.1139/b85-005 ◽

1985 ◽

Vol 63 (1) ◽

pp. 25-35 ◽

Cited By ~ 36

Author(s):

Susan A. Lancelle ◽

John G. Torrey

Keyword(s):

Apical Meristem ◽

Root Nodules ◽

Lateral Roots ◽

Infected Tissue ◽

Host Cells ◽

Outer Cortex ◽

Infection Threads ◽

Thread Formation ◽

Mature Nodule ◽

Inner Cortex

The Rhizobium-induced root nodules of Parasponia rigida (Ulmaceae) outwardly resemble those formed on actinorhizal plants, being coralloid in shape and consisting of multiple, branched lobes. The details of nodule morphogenesis also resemble more closely those which occur in an actinorhizal association than a typical Rhizobium–legume association and include prenodule formation, initiation of modified lateral roots which are termed nodule lobe primordia, and rhizobial colonization of tissues derived from the nodule lobe primordia to form the primary nodule lobes. Mature nodule lobe structure is actinorhizallike. Each lobe has an apical meristem and a central vascular cylinder which is surrounded by an uninfected inner cortex and then a zone of infected tissue. Peripheral to the infected tissue is an uninfected outer cortex. Infection threads and intercellular rhizobia progress continuously toward the apical meristem but do not infect the meristem itself. The establishment of the symbiosis in the host cells involves continuous thread formation after the initial infection until the host cells are nearly filled with rhizobia enclosed in threads. The rhizobia remain in threads throughout the symbiotic relationship and are not released from the threads as occurs in bacteroid formation in legumes.

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A comprehensive RNA-Seq-based gene expression atlas of the summer squash (Cucurbita pepo) provides insights into fruit morphology and ripening mechanisms

BMC Genomics ◽

10.1186/s12864-021-07683-2 ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Aliki Xanthopoulou ◽

Javier Montero-Pau ◽

Belén Picó ◽

Panagiotis Boumpas ◽

Eleni Tsaliki ◽

...

Keyword(s):

Gene Expression ◽

Cucurbita Pepo ◽

Developmental Stages ◽

Lateral Roots ◽

Expression Patterns ◽

Male Flower ◽

Differentially Expressed ◽

Gene Expression Atlas ◽

Summer Squash ◽

Expression Atlas

Abstract Background Summer squash (Cucurbita pepo: Cucurbitaceae) are a popular horticultural crop for which there is insufficient genomic and transcriptomic information. Gene expression atlases are crucial for the identification of genes expressed in different tissues at various plant developmental stages. Here, we present the first comprehensive gene expression atlas for a summer squash cultivar, including transcripts obtained from seeds, shoots, leaf stem, young and developed leaves, male and female flowers, fruits of seven developmental stages, as well as primary and lateral roots. Results In total, 27,868 genes and 2352 novel transcripts were annotated from these 16 tissues, with over 18,000 genes common to all tissue groups. Of these, 3812 were identified as housekeeping genes, half of which assigned to known gene ontologies. Flowers, seeds, and young fruits had the largest number of specific genes, whilst intermediate-age fruits the fewest. There also were genes that were differentially expressed in the various tissues, the male flower being the tissue with the most differentially expressed genes in pair-wise comparisons with the remaining tissues, and the leaf stem the least. The largest expression change during fruit development was early on, from female flower to fruit two days after pollination. A weighted correlation network analysis performed on the global gene expression dataset assigned 25,413 genes to 24 coexpression groups, and some of these groups exhibited strong tissue specificity. Conclusions These findings enrich our understanding about the transcriptomic events associated with summer squash development and ripening. This comprehensive gene expression atlas is expected not only to provide a global view of gene expression patterns in all major tissues in C. pepo but to also serve as a valuable resource for functional genomics and gene discovery in Cucurbitaceae.

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Midline signalling is required for Pax gene regulation and patterning of the eyes

Development ◽

10.1242/dev.121.10.3267 ◽

1995 ◽

Vol 121 (10) ◽

pp. 3267-3278 ◽

Cited By ~ 72

Author(s):

R. Macdonald ◽

K.A. Barth ◽

Q. Xu ◽

N. Holder ◽

I. Mikkola ◽

...

Keyword(s):

Developmental Stages ◽

Pigment Epithelium ◽

Neural Retina ◽

Protein Distribution ◽

Optic Stalk ◽

Retinal Tissue ◽

Pax6 Protein ◽

Signalling Molecule ◽

Pax Family ◽

In Cells

Pax6 and Pax2 are members of the Pax family of transcription factors that are both expressed in the developing visual system of zebrafish embryos. Pax6 protein is present in all cells that form the neural retina and pigment epithelium, whereas Pax2 is located primarily in cells that will give rise to the optic stalk. In this study, we have addressed the role of midline signalling in the regulation of Pax2 and Pax6 distributions and in the subsequent morphogenesis of the eyes. Midline signalling is severely perturbed in cyclops mutant embryos resulting in an absence of ventral midline CNS tissue and fusion of the eyes. Mutant embryos ectopically express Pax6 in a bridge of tissue around the anterior pole of the neural keel in the position normally occupied by cells that form the optic stalks. In contrast, Pax2 protein is almost completely absent from this region in mutant embryos. Concommitant with the changes in Pax protein distribution, cells in the position of the optic stalks differentiate as retina. These results suggest that a signal emanating from the midline, which is absent in cyclops mutant embryos, may be required to promote Pax2 and inhibit Pax6 expression in cells destined to form the optic stalks. Sonic hedgehog (Shh also known as Vhh-1 and Hhg-1) is a midline signalling molecule that is absent from the neuroepithelium of cyclops mutant embryos at early developmental stages. To test the possibility that Shh might be able to regulate the spatial expression of Pax6 and Pax2 in the optic primordia, it was overexpressed in the developing CNS. The number of cells containing Pax2 was increased following shh overexpression and embryos developed hypertrophied optic stalk-like structures. Complimentary to the changes in Pax2 distribution, there were fewer Pax6-containing cells and pigment epithelium and neural retina were reduced. Our results suggest that Shh or a closely related signalling molecule emanating from midline tissue in the ventral forebrain either directly or indirectly induces the expression of Pax2 and inhibits the expression of Pax6 and thus may regulate the partitioning of the optic primordia into optic stalks and retinal tissue.

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MULTIVARIATE ANALYSIS OF THE POPULATION STRUCTURE OF SITONA HISPIDULUS (COLEOPTERA: CURCULIONIDAE) IN ALFALFA FIELD SOIL

The Canadian Entomologist ◽

10.4039/ent118517-6 ◽

1986 ◽

Vol 118 (6) ◽

pp. 517-524 ◽

Cited By ~ 5

Author(s):

M.A. Quinn ◽

A.A. Hower

Keyword(s):

Population Structure ◽

Canonical Correlation ◽

Developmental Stages ◽

Root Nodules ◽

Field Soil ◽

Multivariate Statistical Techniques ◽

Multivariate Statistical ◽

Sitona Hispidulus ◽

Small Root ◽

Alfalfa Field

AbstractThe multivariate statistical techniques of canonical correlation and canonical redundancy analyses were used to assess the population structure of larvae of Sitona hispidulus (F.) in alfalfa field soil. A series of rhizosphere variables was correlated with a series of insect variables that represented the developmental stages of the insect to identify relationships between the insect and rhizosphere. Results indicated that 1st and 2nd-instar larvae were correlated with small root nodules and soil moisture, but not with taproot biomass. Third- and 4th-instar larvae and pupae were not correlated with any of the rhizosphere components measured. Fifth-instar larvae were associated with taproot biomass.

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Colonization and invasion of peanut (Arachis hypogaea L.) roots by gusA-marked Bradyrhizobium sp.

Canadian Journal of Botany ◽

10.1139/b01-050 ◽

2001 ◽

Vol 79 (6) ◽

pp. 733-738 ◽

Cited By ~ 2

Author(s):

Eiji Uheda ◽

Hiroyuki Daimon ◽

Fumiki Yoshizako

Keyword(s):

Cell Wall ◽

Arachis Hypogaea ◽

Hair Cells ◽

Root Hair ◽

Root Nodules ◽

Lateral Roots ◽

Middle Lamella ◽

Root Surface ◽

Arachis Hypogaea L ◽

Root Hair Cells

Tufted rosettes of long root hairs occur in axils of young lateral roots of peanut (Arachis hypogaea L.). Analyses of serial sections of the axils of emerging lateral roots revealed multiple layers of root hair cells. The cells of the outer layer partially overlie the adjacent cells of the inner layer. When Bradyrhizobium cells with an integrated gusA gene were inoculated onto peanut roots and the roots subsequently stained with X-gluc, blue spots indicating the presence of colonies of Bradyrhizobium were observed in the axils of lateral roots. Blue spots were also observed in other areas on the root surface. Transmission electron microscopy revealed that the primary wall of the base of root hair cells has a loose construction. Upon inoculation of Bradyrhizobium, bacteria entered only between root hair cells through the middle lamella. In other areas of the root surface other than axils of lateral roots, the cells had modified walls similar to those at the base of root hair cells. However, invasion by Bradyrhizobium of the cell wall was not observed.Key words: Arachis hypogaea, gusA-marked Bradyrhizobium, cell wall, invasion, root hair cell, root nodules.

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Developmental stages of Sphaerospora ohlmacheri (Whinery, 1893) n.comb. (Myxozoa: Myxosporea) in the renal tubules of bullfrog tadpoles, Rana catesbeiana, from Lake of Two Rivers, Algonquin Park, Ontario

Canadian Journal of Zoology ◽

10.1139/z86-335 ◽

1986 ◽

Vol 64 (10) ◽

pp. 2213-2217 ◽

Cited By ~ 13

Author(s):

Sherwin S. Desser ◽

Jǐrí Lom ◽

Iva Dyková

Keyword(s):

Developmental Stages ◽

Renal Tubule ◽

Rana Catesbeiana ◽

Renal Tubules ◽

Histological Sections ◽

Tubule Cells ◽

Bowman's Capsule

Pseudoplasmodia and mature spores of Sphaerospora ohlmacheri (Whinery, 1893) n.comb. were found in the renal tubules and in the space of the Bowman's capsule of 2nd-year tadpoles of the bullfrog, Rana catesbeiana. Fresh spores and the sporogenic stages of S. ohlmacheri from tissue imprints and histological sections are described and illustrated. Dystrophic changes of renal tubule cells characterized by degeneration associated with hyaline droplets often accompanied the presence of the parasite. Features of the genera Leptotheca, Wardia, and Sphaerospora are discussed.

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The rhizobial autotransporter determines the symbiotic nitrogen fixation activity of Lotus japonicus in a host-specific manner

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1913349117 ◽

2020 ◽

Vol 117 (3) ◽

pp. 1806-1815 ◽

Cited By ~ 2

Author(s):

Yoshikazu Shimoda ◽

Yuki Nishigaya ◽

Hiroko Yamaya-Ito ◽

Noritoshi Inagaki ◽

Yosuke Umehara ◽

...

Keyword(s):

Nitrogen Fixation ◽

Host Plant ◽

Symbiotic Nitrogen Fixation ◽

Root Nodules ◽

Lotus Japonicus ◽

Dependent Manner ◽

Strain Specificity ◽

Passenger Domain ◽

Aspartic Peptidase ◽

Specific Manner

Leguminous plants establish endosymbiotic associations with rhizobia and form root nodules in which the rhizobia fix atmospheric nitrogen. The host plant and intracellular rhizobia strictly control this symbiotic nitrogen fixation. We recently reported a Lotus japonicus Fix− mutant, apn1 (aspartic peptidase nodule-induced 1), that impairs symbiotic nitrogen fixation. APN1 encodes a nodule-specific aspartic peptidase involved in the Fix− phenotype in a rhizobial strain-specific manner. This host-strain specificity implies that some molecular interactions between host plant APN1 and rhizobial factors are required, although the biological function of APN1 in nodules and the mechanisms governing the interactions are unknown. To clarify how rhizobial factors are involved in strain-specific nitrogen fixation, we explored transposon mutants of Mesorhizobium loti strain TONO, which normally form Fix− nodules on apn1 roots, and identified TONO mutants that formed Fix+ nodules on apn1. The identified causal gene encodes an autotransporter, part of a protein secretion system of Gram-negative bacteria. Expression of the autotransporter gene in M. loti strain MAFF3030399, which normally forms Fix+ nodules on apn1 roots, resulted in Fix− nodules. The autotransporter of TONO functions to secrete a part of its own protein (a passenger domain) into extracellular spaces, and the recombinant APN1 protein cleaved the passenger protein in vitro. The M. loti autotransporter showed the activity to induce the genes involved in nodule senescence in a dose-dependent manner. Therefore, we conclude that the nodule-specific aspartic peptidase, APN1, suppresses negative effects of the rhizobial autotransporter in order to maintain effective symbiotic nitrogen fixation in root nodules.

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FrankiaDiversity in Host Plant Root Nodules Is Independent of Abundance or Relative Diversity ofFrankiaPopulations in Corresponding Rhizosphere Soils

Applied and Environmental Microbiology ◽

10.1128/aem.02248-17 ◽

2017 ◽

Vol 84 (5) ◽

Cited By ~ 3

Author(s):

Seifeddine Ben Tekaya ◽

Trina Guerra ◽

David Rodriguez ◽

Jeffrey O. Dawson ◽

Dittmar Hahn

Keyword(s):

Host Plant ◽

Root Nodule ◽

Root Nodules ◽

Actinorhizal Plants ◽

Nodule Formation ◽

Nitrogen Fixing ◽

Content Type ◽

Rhizosphere Soils ◽

Root Nodule Formation ◽

Host Infection

ABSTRACTActinorhizal plants form nitrogen-fixing root nodules in symbiosis with soil-dwelling actinobacteria within the genusFrankia, and specificFrankiataxonomic clusters nodulate plants in corresponding host infection groups. In same-soil microcosms, we observed that some host species were nodulated (Alnus glutinosa,Alnus cordata,Shepherdia argentea,Casuarina equisetifolia) while others were not (Alnus viridis,Hippophaë rhamnoides). Nodule populations were represented by eight different sequences ofnifHgene fragments. Two of these sequences characterized frankiae inS. argenteanodules, and three others characterized frankiae inA. glutinosanodules. Frankiae inA. cordatanodules were represented by five sequences, one of which was also found in nodules fromA. glutinosaandC. equisetifolia, while another was detected in nodules fromA. glutinosa. Quantitative PCR assays showed that vegetation generally increased the abundance of frankiae in soil, independently of the target gene (i.e.,nifHor the 23S rRNA gene). Targeted Illumina sequencing ofFrankia-specificnifHgene fragments detected 24 unique sequences from rhizosphere soils, 4 of which were also found in nodules, while the remaining 4 sequences in nodules were not found in soils. Seven of the 24 sequences from soils represented >90% of the reads obtained in most samples; the 2 most abundant sequences from soils were not found in root nodules, and only 2 of the sequences from soils were detected in nodules. These results demonstrate large differences between detectableFrankiapopulations in soil and those in root nodules, suggesting that root nodule formation is not a function of the abundance or relative diversity of specificFrankiapopulations in soils.IMPORTANCEThe nitrogen-fixing actinobacteriumFrankiaforms root nodules on actinorhizal plants, with members of specificFrankiataxonomic clusters nodulating plants in corresponding host infection groups. We assessedFrankiadiversity in root nodules of different host plant species, and we related specific populations to the abundance and relative distribution of indigenous frankiae in rhizosphere soils. Large differences were observed between detectableFrankiapopulations in soil and those in root nodules, suggesting that root nodule formation is not a function of the abundance or relative diversity of specificFrankiapopulations in soils but rather results from plants potentially selecting frankiae from the soil for root nodule formation. These data also highlight the necessity of using a combination of different assessment tools so as to adequately address methodological constraints that could produce contradictory data sets.

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