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

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.

scholarly journals Regulation of Pathogenic Spore Germination by CgRac1 in the Fungal Plant Pathogen Colletotrichum gloeosporioides

2011 ◽  
Vol 10 (8) ◽  
pp. 1122-1130 ◽  
Author(s):  
Iris Nesher ◽  
Anna Minz ◽  
Leonie Kokkelink ◽  
Paul Tudzynski ◽  
Amir Sharon
Keyword(s):  
Cell Division ◽  
Plant Pathogen ◽  
Germ Tube ◽  
Colletotrichum Gloeosporioides ◽  
Fluorescent Protein ◽  
Nuclear Division ◽  
Simultaneous Formation ◽  
Content Type ◽  
Germ Tubes

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.

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

2004 ◽  
Vol 164 (4) ◽  
pp. 581-591 ◽  
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.

ROOT EXUDATES FROM RED PINE SEEDLINGS AND THEIR EFFECTS ON PYTHIUM ULTIMUM

1967 ◽  
Vol 45 (7) ◽  
pp. 1031-1040 ◽  
Author(s):  
V. P. Agnihotri ◽  
O. Vaartaja
Keyword(s):  
Amino Acids ◽  
Root Exudates ◽  
Root Exudate ◽  
Pinus Resinosa ◽  
Pythium Ultimum ◽  
Gamma Amino Butyric Acid ◽  
Amino Butyric Acid ◽  
Pine Seedlings ◽  
Germ Tubes

The role of root exudates in interaction between pine roots (Pinus resinosa Ait.) and Pythium ultimum Trow was studied. By paper chromatographic methods three sugars and 13 amino acids were definitely identified in the root exudate. Gamma amino butyric acid was most abundant, although asparagine, glycine, serine, and alanine were also present in large amounts. Valine, leucine, glutamine, aspartic acid, glutamic acid and proline were detected in smaller quantities. Among the sugars, both glucose and fructose were abundant while traces of arabinose were detected. When supplied singly, all amino acids and sugars except serine, leucine and arabinose, stimulated growth of the pathogen and germination of sporangia. Mixtures of sugars or mixtures of three or four amino acids were very effective in stimulating mycelial growth and development of germ tubes. The kind of nutrient influenced the number of germ tubes per sporangium. Favorable nutrient combinations, viz. mixtures of sugars, mixtures of three or four amino acids or root exudate solution, produced two to nine germ tubes, while unfavorable ones, viz., glycine, arabinose and serine, etc., produced one or two germ tubes.

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

1968 ◽  
Vol 46 (9) ◽  
pp. 1135-1141 ◽  
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.

scholarly journals Rhinocerotidae from the early Miocene of the Negev (Israel) and implications for the dispersal of early Neogene rhinoceroses

2021 ◽  
pp. 1-12
Author(s):  
Luca Pandolfi ◽  
Ran Calvo ◽  
Ari Grossman ◽  
Rivka Rabinovich
Keyword(s):  
Southeast Asia ◽  
South Asian ◽  
North Africa ◽  
Range Expansion ◽  
New Records ◽  
Ct Scanning ◽  
Early Miocene ◽  
Early Neogene ◽  
Postcranial Remains

Abstract A revision of the rhinocerotid material from the Negev (Israel), dating back to the early Miocene (MN3 in the European Mammal Biochronology), highlights the presence of Brachypotherium and a taxon close to Gaindatherium in the Levantine corridor. A juvenile mandible, investigated using CT scanning, displays morphologically distinct characters consistent with Brachypotherium cf. B. snowi rather than with other Eurasian representatives of this genus. Some postcranial remains from the Negev, such as a humerus, display features that distinguish it among Miocene taxa. We attribute these postcrania to cf. Gaindatherium sp., a taxon never recorded outside the Siwaliks until now. This taxon dispersed into the Levantine region during the late early Miocene, following a pattern similar to other South Asian taxa. Brachypotherium cf. B. snowi probably occurred in the Levantine region and then in North Africa during the early Miocene because its remains are known from slightly younger localities such as Moghara (Egypt) and Jebel Zelten (Libya). The occurrence cf. Gaindatherium sp. represents a previously unrecorded range expansion out of Southeast Asia. These new records demonstrate the paleogeographic importance of the Levantine region showcasing the complex role of the Levantine corridor in intercontinental dispersals between Asia and Europe as well as Eurasia and Africa.

scholarly journals Magnetic Survey at the Roman Military Camp of el Benian in Mauretania Tingitana (Morocco): Results and Implications

2020 ◽  
Vol 13 (1) ◽  
pp. 28
Author(s):  
Francesco Martorella
Keyword(s):  
Roman Empire ◽  
North Africa ◽  
Geophysical Survey ◽  
Magnetic Survey ◽  
North East ◽  
The North ◽  
Military Camp ◽  
Building Activity ◽  
Economic Studies

The topic of military settlements and the role of troops in the northern provinces of North Africa during the age of the Roman Empire has recently gained a strong interest in historical, archaeological, epigraphical, and economic studies. In particular, at Mauretania Tingitana (in the north-east area of modern-day Morocco), the presence of numerous military camps in the Early and Later Roman Empire has now been assessed. In this framework, the present work deals with the geophysical survey, by means of magnetometry, at the site of el Benian, where the largest military camp is located. In particular, the magnetic survey has highlighted the organization of the camp, almost totally unknown previously. The result of the magnetic survey has confirmed intense building activity over the centuries and made it possible to identify and characterize the structures typical of a military field.

Events in Northern Africa and Middle East: Causes and Consequences

2011 ◽  
pp. 11-25
Author(s):  
I. Labinskaya
Keyword(s):  
Middle East ◽  
North Africa ◽  
Large Scale ◽  
Arab Countries ◽  
Northern Africa ◽  
External Factors ◽  
Wide Range ◽  
The Usa ◽  
Oriental Studies

Political developments in North Africa and the Middle East that have begun in January 2011 are gaining strength and involve an increasing number of Arab countries. The participants of the Roundtable – experts from IMEMO, Institute of Oriental Studies (RAS), Institute of the USA and Canada (RAS) and Mrs. E. Suponina from “Moscow News” newspaper analyzed a wide range of issues associated with these events. Among them are: 1) the reasons for such a large-scale explosion, 2) the nature of the discussed developments (revolutions, riots?) and who are the subjects of the current “Arab drama”, 3) the role of Islam and political Islamism, 4) the role of external factors.

The Hellenistic and Byzantine Defences of Tocra (Taucheira)

1998 ◽  
Vol 29 ◽  
pp. 35-83 ◽  
Author(s):  
David Smith ◽  
James Crow
Keyword(s):  
North Africa ◽  
Outer Wall ◽  
Seventh Century ◽  
The South ◽  
The West ◽  
Curtain Wall ◽  
South Side ◽  
Sea Wall ◽  
The City

AbstractThe fortifications of the Hellenistic and Roman city of Tocra are over 2 km long (including the sea-wall) and comprise a curtain wall up to 2 m wide flanked by 31 rectangular towers. Three main structural phases were noted in the survey carried out in 1966 by David Smith: (1) Hellenistic walls of isodomic ashlar, (2) later Hellenistic work of isodomic ashlar with bevelled edges, associated with the indented trace along the south rampart, and (3) an extensive rebuild of plain ashlar blocks including the towers and reconstruction to the East and West Gates, dateable, on the basis of Procopius, to the reign of Justinian. The general significance of the fortifications at Tocra is considered in the second part: these include the Hellenistic indented trace along the south side, later reinforced by towers in the sixth century AD. Also of wider importance was the use of an outer wall or proteichisma, and the pentagonal, pointed towers at the two main gates. Both these elements were unusual in Byzantine North Africa and they are discussed as part of the more general repertory of Byzantine fortifications. The unusual tower adjacent to the West Church is considered in the context of literary accounts. The article concludes by considering how the architecture and magnitude of the fortifications can allow a reassessment of the wider role of the city in the sixth and seventh century defences of Cyrenaica.

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