The role of primary germ tubes (PGT) in the life cycle of Blumeria graminis: The stopping of PGT elongation is necessary for the triggering of appressorial germ tube (AGT) emergence

ABSTRACT Colletotrichum gloeosporioides is a facultative plant pathogen: it can live as a saprophyte on dead organic matter or as a pathogen on a host plant. Different patterns of conidial germination have been recognized under saprophytic and pathogenic conditions, which also determine later development. Here we describe the role of CgRac1 in regulating pathogenic germination. The hallmark of pathogenic germination is unilateral formation of a single germ tube following the first cell division. However, transgenic strains expressing a constitutively active CgRac1 (CA-CgRac1) displayed simultaneous formation of two germ tubes, with nuclei continuing to divide in both cells after the first cell division. CA-CgRac1 also caused various other abnormalities, including difficulties in establishing and maintaining cell polarity, reduced conidial and hyphal adhesion, and formation of immature appressoria. Consequently, CA-CgRac1 isolates were completely nonpathogenic. Localization studies with cyan fluorescent protein (CFP)-CgRac1 fusion protein showed that the CgRac1 protein is abundant in conidia and in hyphal tips. Although the CFP signal was equally distributed in both cells of a germinating conidium, reactive oxygen species accumulated only in the cell that produced a germ tube, indicating that CgRac1 was active only in the germinating cell. Collectively, our results show that CgRac1 is a major regulator of asymmetric development and that it is involved in the regulation of both morphogenesis and nuclear division. Modification of CgRac1 activity disrupts the morphogenetic program and prevents fungal infection.

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Nuclear behavior and clarification of the spore stages of Uromyces koae

Canadian Journal of Botany ◽

10.1139/b81-128 ◽

1981 ◽

Vol 59 (5) ◽

pp. 939-946 ◽

Cited By ~ 14

Author(s):

Donald E. Gardner

Keyword(s):

Life Cycle ◽

Meiotic Division ◽

Germ Tube ◽

Nuclear Staining ◽

Diploid Nucleus ◽

Spore Type ◽

Acacia Koa ◽

Nuclear Behavior ◽

Germ Tubes

Recent observations showed that Uromyces koae Arthur in Stevens teliospores did not produce typical basidia or basidio-spores. The present study reveals that teliospores produced long germ tubes that are differentiated into wide proximal and narrow distal portions separated by a vesiclelike swelling. One or two extensive branches, each morphologically resembling the main tube, developed from individual germ tube cells. Nuclear staining revealed a single, presumably diploid nucleus in mature teliospores. One or more probable mitotic divisions in the main germ tube provided a diploid nucleus for each branch and for the main tube itself. Meiotic division of each nucleus produced a series of four smaller nuclei in the narrow portion of each branch and the main tube. The germ tubes may be modified basidia and serve as infectious hyphae in place of basidiospores.A formerly undescribed spore type associated with the teliospores is recognized as uredinial. This investigation shows that the life cycle of U. koae probably consists of four distinct stages, each on Acacia koa: the spermatial associated with the aecial on hypertrophied shoots, and the uredinial and telial together in discrete leaf pustules.

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CYTOLOGY OF THE AECIOSPORES AND AECIOSPORE GERM TUBES OF PERIDERMIUM HARKNESSII AND P. STALACTIFORME OF THE CRONARTIUM COLEOSPORIOIDES COMPLEX

Canadian Journal of Botany ◽

10.1139/b66-175 ◽

1966 ◽

Vol 44 (12) ◽

pp. 1639-1643 ◽

Cited By ~ 17

Author(s):

Y. Hiratsuka ◽

W. Morf ◽

J. M. Powell

Keyword(s):

Life Cycle ◽

Germ Tube ◽

Nuclear Division ◽

Nuclear Fusion ◽

Septum Formation ◽

Germ Tubes

Cytology of aeciospores and aeciospore germ tubes of two pine rusts, Peridermium harknessii J. P. Moore and P. stalactiforme Arth. & Kern, was compared. In P. harknessii the mycelial cells giving rise to aecia were uninucleate. Young aeciospores were usually binucleate but most of them became uninucleate during maturation. Upon germination, nuclear division and septum formation occurred and germ tubes were divided into two, three, or four cells, each of which usually contained one nucleus. One to three side branches developed and nuclei migrated into them. Basidiospores were not produced. Despite the absence of basidiospores, P. harknessii is interpreted as having an endo-type life cycle with nuclear fusion and meiosis. In P. stalactiforme, aeciospores were binucleate and, upon germination, two nuclei migrated into the germ tube. The nuclei remained undivided during the formation of appressoria and infection pegs. Septa were not observed and branching was dichotomous or irregular.

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In Candida albicans, the Nim1 kinases Gin4 and Hsl1 negatively regulate pseudohypha formation and Gin4 also controls septin organization

The Journal of Cell Biology ◽

10.1083/jcb.200307176 ◽

2004 ◽

Vol 164 (4) ◽

pp. 581-591 ◽

Cited By ~ 77

Author(s):

Raymond Wightman ◽

Steven Bates ◽

Pat Amornrrattanapan ◽

Peter Sudbery

Keyword(s):

Candida Albicans ◽

Germ Tube ◽

Ectopic Expression ◽

Tube Formation ◽

Septin Ring ◽

Germ Tubes ◽

Developmental Switch

In the development of hyphal germ tubes of Candida albicans, a band of septin forms at the base of the germ tube (basal septin band). Later, a septin ring forms, which organizes the first septum within the germ tube (septin ring). We have investigated the role of the Nim1 kinases, Gin4 and Hsl1, in the formation of these septin structures. We show that during germ tube formation, Gin4 is required for the organization of the septin ring but not the basal septin band. Hsl1 is not required for the formation of either septin rings or basal bands. Unexpectedly, we found that both gin4Δ and hsl1Δ mutants form pseudohyphae constitutively, in a fashion that in the case of gin4Δ, is partly independent of Swe1. Gin4-depleted pseudohyphae are unable to form hyphae when challenged with serum, but this can be overcome by ectopic expression of Gin4 from the MET3 promoter. Thus, Gin4 may regulate the developmental switch from pseudohyphae to hyphae.

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Morphology and cytology of aeciospores and aeciospore germ tubes of host-alternating and pine-to-pine races of Cronartium flaccidum in northern Europe

Canadian Journal of Botany ◽

10.1139/b68-147 ◽

1968 ◽

Vol 46 (9) ◽

pp. 1119-1122 ◽

Cited By ~ 25

Author(s):

Y. Hiratsuka

Keyword(s):

Life Cycle ◽

Pinus Sylvestris ◽

Germ Tube ◽

Nuclear Division ◽

Nuclear Fusion ◽

Northern Europe ◽

Septum Formation ◽

Germ Tubes ◽

Irregular Growth

Host-alternating and pine-to-pine races of Cronartium flaccidum (Alb. & Schw.) Wint. (Peridermium pint Lév.) on Pinus sylvestris L. from northern Europe can be distinguished by differences in the morphology and cytology of aeciospores and aeciospore germ tubes. In the host alternating race, aeciospores were binucleate and, upon germination, two nuclei migrated into the germ tube. The nuclei remained undivided during migration. Septa were not observed and branching was dichotomous and irregular. Growth of germ tubes was indeterminate.In the pine-to-pine race, aeciospores were mostly binucleate but variable proportions (16% to 28%) were uninucleate. Upon germination nuclear division and septum formation occurred and the germ tubes were transformed into two, three, or four cells, each of which usually contained one nucleus. The germ tubes were straight and seldom exceeded 200 μ in length. One to three branches were observed. Despite the absence of basidiospores, the pine-to-pine race of C. flaccidum (= P. pini) is interpreted as having an endo-type life cycle with or without nuclear fusion and typical meiosis.

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Seed exudates from Pinus resinosa and their effects on growth and zoospore germination of Pythium afertile

Canadian Journal of Botany ◽

10.1139/b68-150 ◽

1968 ◽

Vol 46 (9) ◽

pp. 1135-1141 ◽

Cited By ~ 17

Author(s):

V. P. Agnihotri ◽

O. Vaartaja

Keyword(s):

Amino Acids ◽

Organic Acids ◽

Germ Tube ◽

Pinus Resinosa ◽

Aminobutyric Acid ◽

Seed Exudate ◽

Germinating Seeds ◽

Germination And Growth ◽

Germ Tubes

The role of exudates from germinating seeds of red pine, Pinus resinosa Ait., was examined in relation to zoospore germination and growth of Pythium afertile Kanouse and Humphrey. By paper chromatography, 14 amino acids, 4 sugars, and 3 organic acids were identified in the seed exudate. Among the sugars, glucose, fructose, and sucrose were detected in large amounts and arabinose in small amounts. Of 14 amino acids identified, threonine, lysine, arginine, and glutamine were present in trace amounts; leucine, γ-aminobutyric acid, valine, asparagine, and alanine in large amounts; and proline, serine, glycine, aspartic acid, and glutamic acid in small amounts. Of three organic acids detected, malonic acid was most abundant whereas citric and fumaric acids were present in small and trace amounts, respectively.When supplied singly, all sugars and amino acids, except alanine, threonine, γ-aminobutyric acid, and arabinose stimulated mycelial growth and germ tube growth of P. afertile. Organic acids promoted no growth and inhibited zoospore germination. Mixtures of sugars and mixtures of three or four amino acids effectively stimulated growth of mycelium and germ tubes. One to three germ tubes were produced with certain amino acids and sugars but only one germ tube with others. There was no correlation between the percentage zoospore germination and length of germ tube.

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Development of primary germ tubes by conidia of Blumeria graminis f.sp. hordei on leaf epidermal cells of Hordeum vulgare

Canadian Journal of Botany ◽

10.1139/b02-092 ◽

2002 ◽

Vol 80 (10) ◽

pp. 1121-1125 ◽

Cited By ~ 19

Author(s):

H H Edwards

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Hordeum Vulgare ◽

Host Cell ◽

Germ Tube ◽

Tube Wall ◽

Blumeria Graminis ◽

Transmission Electron ◽

Host Cell Wall ◽

Germ Tubes

Development of primary germ tubes from conidia of Blumeria graminis f.sp. hordei on primary leaf segments of Hordeum vulgare was investigated from 3 to 13 h postinoculation (hpi) using transmission electron microscopy. By 3 hpi, the primary germ tube wall that makes contact with the host cuticle develops a small protrusion that breaches the host cuticle and touches the host cell wall but does not penetrate any further. This protrusion is the cuticular peg. From 3 to 13 hpi, the cuticular peg swells, becomes quite electron dense, and finally develops a loose fibrillar texture. The structure of the primary germ tube with the terminal cuticular peg is consistent with the hypothesis that it allows the conidium to absorb water and solutes present in the host cell wall.Key words: powdery mildew, barley, ultrastructure.

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Costunolide Influences Germ Tube Orientation in Sunflower Broomrape – A First Step Toward Understanding Chemotropism

Frontiers in Plant Science ◽

10.3389/fpls.2021.699068 ◽

2021 ◽

Vol 12 ◽

Author(s):

Anna Krupp ◽

Barbara Bertsch ◽

Otmar Spring

Keyword(s):

Root Exudates ◽

North Africa ◽

Germ Tube ◽

Sesquiterpene Lactones ◽

Host Root ◽

Germination Stimulants ◽

Root Parasite ◽

Sunflower Broomrape ◽

Germ Tubes

Orobanche cumana WALLR. is a host-specific root parasite of cultivated sunflowers with increasing economic importance in Europe, North Africa, and parts of Asia. While sesquiterpene lactones (STLs) released from sunflower roots were identified as natural germination stimulants of O. cumana seeds in the soil, the chemical nature of the signals guiding the emerging germ tube toward the host root has remained unknown hitherto. Thus, we designed a bioassay that allowed the observation of broomrape germination and subsequent germ tube development in the presence of substances with putative chemotropic activity. Root exudates and sunflower oil extracts, both containing STLs in micromolar concentrations, caused the positive chemotropic orientation of germ tubes. A similar positive chemotropic effect was achieved with costunolide, one of the four STLs of sunflower present in the exudate and oil extracts. In contrast, GR24, a synthetic strigolactone (SL) with germination-inducing activity on O. cumana seeds, showed no effect on the germ tube orientation. The effect of costunolide was concentration-dependent and within the range of its natural micromolar occurrence in roots. We assume that an STL gradient is responsible for the stronger inhibition of elongation growth on the host-facing flank of the germ tube compared with the far side flank. This would confer a double role of STLs from sunflower root exudates in the sunflower–broomrape interaction, namely, as germination stimulants and as chemotropic signals.

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ASPECTS IN BUILDING A COMPANY WEB-SITE AND ITS ROLE FOR THE DEVELOPMENT OF BUSINESS

International Conference on Technics Technologies and Education ◽

10.15547/ictte.04.001 ◽

2018 ◽

pp. 117-124

Author(s):

Petar Halachev ◽

Victoria Radeva ◽

Albena Nikiforova ◽

Miglena Veneva

Keyword(s):

Life Cycle ◽

Web Site ◽

The Internet ◽

A Company ◽

The Web ◽

Design Construction ◽

Made In ◽

Site Types

This report is dedicated to the role of the web site as an important tool for presenting business on the Internet. Classification of site types has been made in terms of their application in the business and the types of structures in their construction. The Models of the Life Cycle for designing business websites are analyzed and are outlined their strengths and weaknesses. The stages in the design, construction, commissioning, and maintenance of a business website are distinguished and the activities and requirements of each stage are specified.

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