scholarly journals Transposon-mediated telomere destabilization: a driver of genome evolution in the blast fungus

2019 ◽  
Author(s):  
Mostafa Rahnama ◽  
Olga Novikova ◽  
John Starnes ◽  
Li Chen ◽  
Shouan Zhang ◽  
...  
Keyword(s):  
Magnaporthe Oryzae ◽  
Tandem Repeats ◽  
In Planta ◽  
Single Spore ◽  
Telomere Repeat ◽  
Restriction Fragments ◽  
Molecular Alterations ◽  
Filamentous Ascomycete ◽  
Rdna Sequences ◽  
Chromosome Alterations

ABSTRACTMagnaporthe oryzae is a filamentous ascomycete fungus that causes devastating diseases of crops that include rice and wheat, and a variety of turf, forage and wild grasses. Strains from ryegrasses possess highly stable chromosome ends that undergo frequent rearrangements during vegetative growth in culture and in planta. Instability is associated with the presence of two related retrotransposons (Magnaporthe oryzaeTelomeric Retrotransposons - MoTeRs) inserted within the telomere repeat tracts. The objective of the present study was to determine the mechanisms by which MoTeRs promote telomere instability. Targeted cloning, restriction mapping, and sequencing of both parental and novel telomeric restriction fragments, along with MinION sequencing of DNA from three single-spore cultures, allowed us to document the molecular alterations for 109 newly-formed telomeres. Rearrangement events included truncations of subterminal rDNA sequences; acquisition of MoTeR insertions by “plain” telomeres; insertion of the MAGGY retrotransposons into MoTeR arrays; expansion and contraction of subtelomeric tandem repeats; MoTeR truncations; duplication and terminalization of internal sequences; and breakage at long, interstitial telomeres generated during MoTeR insertion. Together, our data show that when MoTeRs invade the telomeres, they can dramatically perturb the integrity of chromosome ends, leading to the generation of unprotected DNA termini whose repair has the potential to generate chromosome alterations that extend well into the genome interior.

scholarly journals Transposon-mediated telomere destabilization: a driver of genome evolution in the blast fungus

2020 ◽  
Author(s):  
Mostafa Rahnama ◽  
Olga Novikova ◽  
John H Starnes ◽  
Shouan Zhang ◽  
Li Chen ◽  
...  
Keyword(s):  
Genome Evolution ◽  
Magnaporthe Oryzae ◽  
Tandem Repeats ◽  
Collateral Damage ◽  
High Frequencies ◽  
Chromosome Architecture ◽  
Molecular Alterations ◽  
Rdna Sequences ◽  
And Function ◽  
Independent Expansion

Abstract The fungus Magnaporthe oryzae causes devastating diseases of crops, including rice and wheat, and in various grasses. Strains from ryegrasses have highly unstable chromosome ends that undergo frequent rearrangements, and this has been associated with the presence of retrotransposons (Magnaporthe oryzae Telomeric Retrotransposons—MoTeRs) inserted in the telomeres. The objective of the present study was to determine the mechanisms by which MoTeRs promote telomere instability. Targeted cloning, mapping, and sequencing of parental and novel telomeric restriction fragments (TRFs), along with MinION sequencing of genomic DNA allowed us to document the precise molecular alterations underlying 109 newly-formed TRFs. These included truncations of subterminal rDNA sequences; acquisition of MoTeR insertions by ‘plain’ telomeres; insertion of the MAGGY retrotransposons into MoTeR arrays; MoTeR-independent expansion and contraction of subtelomeric tandem repeats; and a variety of rearrangements initiated through breaks in interstitial telomere tracts that are generated during MoTeR integration. Overall, we estimate that alterations occurred in approximately sixty percent of chromosomes (one in three telomeres) analyzed. Most importantly, we describe an entirely new mechanism by which transposons can promote genomic alterations at exceptionally high frequencies, and in a manner that can promote genome evolution while minimizing collateral damage to overall chromosome architecture and function.

scholarly journals Sensitivity of Mycosphaerella fijiensis from Banana to Trifloxystrobin

Plant Disease ◽  
2001 ◽  
Vol 85 (12) ◽  
pp. 1264-1270 ◽  
Author(s):  
K. M. Chin ◽  
M. Wirz ◽  
D. Laird
Keyword(s):  
Cross Resistance ◽  
In Vitro Tests ◽  
Mycosphaerella Fijiensis ◽  
In Planta ◽  
Baseline Sensitivity ◽  
Single Spore ◽  
Resistance Factors ◽  
Development Site ◽  
Disease Pressure

An ascospore germination method was developed and validated to assess the sensitivity of bulk samples of Mycosphaerella fijiensis to trifloxystrobin. Using this method, the sensitivity of 142 ascospore samples from banana plantations not treated with strobilurins was analyzed to establish a baseline of pathogen sensitivity. A bulk method was utilized for monitoring purposes because it avoids potential complications due to the isolation and propagation of single-spore isolates and enables the testing of larger samples. Following intensive use of strobilurins (6 to 11 applications per year) over 4 years, under conditions of high disease pressure and the absence of sanitary measures at a development site in Costa Rica, bulk samples with 50% effective concentration (EC50) resistance factors (RFs) in excess of 500 compared with the mean baseline sensitivity were detected. Single-ascospore isolates derived from spores germinating at the discriminatory dose of 3 μg/ml were also resistant, suggesting that the frequency of resistant individuals in bulk samples could be estimated from the relative numbers of ascospores growing at this dose. The resistance of selected isolates was confirmed in planta. In vitro tests with four resistant and two sensitive single-ascospore isolates collected from different locations and times indicated possible cross-resistance of trifloxystrobin to azoxystrobin, famoxadone, and fenamidone, but not to propiconazole.

A User-Friendly Method to Isolate and Single Spore the Fungi Magnaporthe oryzae and Magnaporthe grisea Obtained from Diseased Field Samples

2009 ◽  
Vol 10 (1) ◽  
pp. 37 ◽  
Author(s):  
Yulin Jia
Keyword(s):  
Magnaporthe Oryzae ◽  
Magnaporthe Grisea ◽  
Single Spore ◽  
Field Samples ◽  
User Friendly

Although M. oryzae has been studied under extensively for several decades worldwide, descriptions of methods for efficient single spore isolation from diseased leaves from the field are not available. The ability to isolate the fungus from field samples is essential for specialists around the globe to study M. oryzae. The objective of this study was to develop a user-friendly method to isolate and evaluate M. oryzae from field samples. Accepted for publication 30 September 2009. Published 15 December 2009.

scholarly journals Structures of Phytophthora RXLR Effector Proteins

2011 ◽  
Vol 286 (41) ◽  
pp. 35834-35842 ◽  
Author(s):  
Laurence S. Boutemy ◽  
Stuart R. F. King ◽  
Joe Win ◽  
Richard K. Hughes ◽  
Thomas A. Clarke ◽  
...  
Keyword(s):  
Immune System ◽  
Molecular Mechanisms ◽  
Tandem Repeats ◽  
Effector Proteins ◽  
Functional Adaptation ◽  
In Planta ◽  
Effector Domains ◽  
The Core ◽  
Plant Immune System ◽  
Molecular Stability

Phytopathogens deliver effector proteins inside host plant cells to promote infection. These proteins can also be sensed by the plant immune system, leading to restriction of pathogen growth. Effector genes can display signatures of positive selection and rapid evolution, presumably a consequence of their co-evolutionary arms race with plants. The molecular mechanisms underlying how effectors evolve to gain new virulence functions and/or evade the plant immune system are poorly understood. Here, we report the crystal structures of the effector domains from two oomycete RXLR proteins, Phytophthora capsici AVR3a11 and Phytophthora infestans PexRD2. Despite sharing <20% sequence identity in their effector domains, they display a conserved core α-helical fold. Bioinformatic analyses suggest that the core fold occurs in ∼44% of annotated Phytophthora RXLR effectors, both as a single domain and in tandem repeats of up to 11 units. Functionally important and polymorphic residues map to the surface of the structures, and PexRD2, but not AVR3a11, oligomerizes in planta. We conclude that the core α-helical fold enables functional adaptation of these fast evolving effectors through (i) insertion/deletions in loop regions between α-helices, (ii) extensions to the N and C termini, (iii) amino acid replacements in surface residues, (iv) tandem domain duplications, and (v) oligomerization. We hypothesize that the molecular stability provided by this core fold, combined with considerable potential for plasticity, underlies the evolution of effectors that maintain their virulence activities while evading recognition by the plant immune system.

Glomus indicum, a new arbuscular mycorrhizal fungus

Botany ◽  
2010 ◽  
Vol 88 (2) ◽  
pp. 132-143 ◽  
Author(s):  
Janusz Błaszkowski ◽  
Tesfaye Wubet ◽  
Variampally Sankar Harikumar ◽  
Przemysław Ryszka ◽  
François Buscot
Keyword(s):  
Plantago Lanceolata ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
Single Species ◽  
Spore Wall ◽  
Fungal Species ◽  
Phylogenetic Position ◽  
Single Spore ◽  
North East ◽  
Rdna Sequences

A new arbuscular mycorrhizal fungal species of the genus Glomus , Glomus indicum (Glomeromycota), forming small, hyaline spores in hypogeous aggregates is described and illustrated. The spores are globose to subglobose, (17–)32(–52) µm in diameter, rarely egg-shaped, oblong to irregular, 17–38 µm × 19–43 µm. The single spore wall of G. indicum consists of two hyaline layers: a mucilaginous, short-lived, thin outer layer staining pinkish to pink in Melzer's reagent and a laminate, smooth, permanent, thicker inner layer. Glomus indicum was found in the rhizosphere of Euphorbia heterophylla  L. naturally growing in coastal sands of Alappuzha in Kerala State of South India and Lactuca sativa  L. cultivated in Asmara, Eritrea, North East Africa. In single-species cultures with Plantago lanceolata  L. as the host plant, G. indicum formed vesicular-arbuscular mycorrhiza. Molecular analysis of the phylogenetic position of G. indicum based on both SSU and ITS rDNA sequences showed the fungus to be a new species with its own cluster. Besides the sites where the spores were observed, sequence types belonging to the G. indicum cluster were documented from environmental samples mainly in the USA, Estonia, and Australia, suggesting the wide occurrence of the species. A key to all known species of the Glomeromycota producing hyaline to light-coloured glomoid spores is provided.

scholarly journals First Report of Guinea Grass Smut Caused by Conidiosporomyces ayresii in Japan

Plant Disease ◽  
2012 ◽  
Vol 96 (1) ◽  
pp. 143-143 ◽  
Author(s):  
T. Tsukiboshi ◽  
M. Ebina ◽  
I. Okabe ◽  
K. Sugawara ◽  
K. Kouki
Keyword(s):  
28S Rdna ◽  
Smut Fungus ◽  
Panicum Maximum ◽  
Single Spore ◽  
First Report ◽  
Perennial Plant ◽  
Rdna Sequences ◽  
Plastic Bags ◽  
Guinea Grass ◽  
28S Rdna Sequence

Guinea grass (Panicum maximum Jacq.) is an important C-4 perennial plant that grows in southern Japan. In March 2010, a smut disease was found in grass that is cultivated in the Ishigaki Islands, Okinawa, in southernmost Japan. Spikelets of susceptible cultivars were swollen and filled with gray spore masses and seed production was substantially reduced. Two single-spore isolates of a smut fungus were obtained from infected spikelets and deposited at the NIAS Genebank, Japan as MAFF511519 and 511520. The 28S rDNA sequences of the isolates were analyzed as described by Boekhout et al. (1). The 28S rDNA sequence (GenBank Accession No. AB647346) of isolate MAFF511519 matched that of Conidiosporomyces ayresii (GenBank Accession No. AY819017) isolated from P. maximum with 99.8% similarity. Spores were pale brown to brown, globose to subglobose, verrucose, and 14 to 16 × 15 to 18 μm in diameter with relatively thick walls of 2 to 3 μm. With scanning electron microscopy, warts appeared dense and short with pointed tips. Spores germinated under wet conditions and produced masses of basidiospores. Basidiospores were aseptate, long, cylindrical, straight to slightly curved, 20 to 37 × 2 to 3 μm, and often germinated into Y-shaped conidia. This description matches previous descriptions (3) of C. ayresii (Berk.) Vánky (Tilletia ayresii Berk.) of the smut pathogen of guinea grass (2). The smut fungus was identified as C. ayresii on the basis of morphology and molecular phylogenetic analysis. To produce inoculum, the isolates were grown on potato dextrose agar at 25°C in the dark for 7 days. Two plants of cv. Ryukyu 5-gou with half-flowering heads were grown in a greenhouse for approximately 1 month and then inoculated by atomizing them with conidial suspensions of each isolate (106 conidia/ml). A plant sprayed with sterilized distilled water served as the control. Inoculated heads were covered with plastic bags for 48 h at 25°C. After 30 days, all inoculated plants were symptomatic with swollen spikelets releasing gray spores. Controls remained asymptomatic. The smut fungus was reisolated from released gray spores, confirming Koch's postulates. To our knowledge, this is the first report of smut caused by C. ayresii on guinea grass in Japan. References: (1) T. Boekhout et al. Stud. Mycol. 38:175, 1995. (2) J. M. Lenné and P. Trutmann. Diseases of Tropical Pasture Plants. CAB International, Wallingford, UK, 1994. (3) K. Vánky and R. Bauer. Mycotaxon 43:427, 1992.

scholarly journals Transcriptome Profiling of the Rice Blast Fungus Magnaporthe oryzae and Its Host Oryza sativa During Infection

2020 ◽  
Vol 33 (2) ◽  
pp. 141-144 ◽  
Author(s):  
Jongbum Jeon ◽  
Gir-Won Lee ◽  
Ki-Tae Kim ◽  
Sook-Young Park ◽  
Seongbeom Kim ◽  
...  
Keyword(s):  
Oryza Sativa ◽  
Magnaporthe Oryzae ◽  
Fungal Pathogen ◽  
Rice Blast ◽  
Transcriptome Profiling ◽  
Transcriptome Data ◽  
Highly Qualified ◽  
In Planta ◽  
Microbe Interactions ◽  
Fungal Genes

The rice blast (fungal pathogen: Magnaporthe oryzae and host: Oryza sativa) is one of the most important model pathosystems for understanding plant–microbe interactions. Although both genome sequences were published as the first cases of pathogen and host, only a few in planta transcriptome data during infection are available. Due to technical difficulties, previously reported fungal transcriptome data are not highly qualified to comprehensively profile the expression of fungal genes during infection. Here, we report the high-quality transcriptomes of M. oryzae and rice during infection using a sheath infection-based RNA sequencing approach. This comprehensive expression profiling of the fungal pathogen and its host will provide a better platform for understanding the plant–microbe interactions at the genomic level and serve as a valuable resource for the research community.

scholarly journals Analysis of in planta Expressed Orphan Genes in the Rice Blast Fungus Magnaporthe oryzae

2014 ◽  
Vol 30 (4) ◽  
pp. 367-374 ◽  
Author(s):  
Md. Abu Sadat ◽  
Junhyun Jeon ◽  
Albely Afifa Mir ◽  
Seongbeom Kim ◽  
Jaeyoung Choi ◽  
...  
Keyword(s):  
Magnaporthe Oryzae ◽  
Rice Blast ◽  
Rice Blast Fungus ◽  
In Planta ◽  
Orphan Genes ◽  
Blast Fungus

scholarly journals Identification and analysis of in planta expressed genes of Magnaporthe oryzae

BMC Genomics ◽  
2010 ◽  
Vol 11 (1) ◽  
pp. 104 ◽  
Author(s):  
Soonok Kim ◽  
Jongsun Park ◽  
Sook-Young Park ◽  
Thomas K Mitchell ◽  
Yong-Hwan Lee
Keyword(s):  
Magnaporthe Oryzae ◽  
In Planta

scholarly journals Endophytic Colonization and In Planta Nitrogen Fixation by a Herbaspirillum sp. Isolated from Wild Rice Species

2001 ◽  
Vol 67 (11) ◽  
pp. 5285-5293 ◽  
Author(s):  
Adel Elbeltagy ◽  
Kiyo Nishioka ◽  
Tadashi Sato ◽  
Hisa Suzuki ◽  
Bin Ye ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Wild Rice ◽  
Fluorescent Protein ◽  
In Planta ◽  
Cultivated Rice ◽  
Phenotypic Properties ◽  
Rice Varieties ◽  
Bacterial Populations ◽  
Rdna Sequences ◽  
Wild Rice Species

ABSTRACT Nitrogen-fixing bacteria were isolated from the stems of wild and cultivated rice on a modified Rennie medium. Based on 16S ribosomal DNA (rDNA) sequences, the diazotrophic isolates were phylogenetically close to four genera: Herbaspirillum,Ideonella, Enterobacter, andAzospirillum. Phenotypic properties and signature sequences of 16S rDNA indicated that three isolates (B65, B501, and B512) belong to the Herbaspirillum genus. To examine whether Herbaspirillum sp. strain B501 isolated from wild rice, Oryza officinalis, endophytically colonizes rice plants, the gfp gene encoding green fluorescent protein (GFP) was introduced into the bacteria. Observations by fluorescence stereomicroscopy showed that the GFP-tagged bacteria colonized shoots and seeds of aseptically grown seedlings of the original wild rice after inoculation of the seeds. Conversely, for cultivated rice Oryza sativa, no GFP fluorescence was observed for shoots and only weak signals were observed for seeds. Observations by fluorescence and electron microscopy revealed that Herbaspirillum sp. strain B501 colonized mainly intercellular spaces in the leaves of wild rice. Colony counts of surface-sterilized rice seedlings inoculated with the GFP-tagged bacteria indicated significantly more bacterial populations inside the original wild rice than in cultivated rice varieties. Moreover, after bacterial inoculation, in planta nitrogen fixation in young seedlings of wild rice, O. officinalis, was detected by the acetylene reduction and 15N2gas incorporation assays. Therefore, we conclude thatHerbaspirillum sp. strain B501 is a diazotrophic endophyte compatible with wild rice, particularly O. officinalis.

Sign in / Sign up

Export Citation Format

Share Document