Papers by Lindsay Triplett
Phytobiomes Journal
Soil bacterial predators that use the biomass of bacterial hosts for growth (multiplication), ene... more Soil bacterial predators that use the biomass of bacterial hosts for growth (multiplication), energy, or replication have the potential to reduce bacterial populations in the wide variety of terrestrial ecosystems in which they are found. Bacterial predators, including bacteria-feeding nematodes, protists, bacteria ( Bdellovibrio and like organisms, Lysobacter, and myxobacteria), and bacteriophages are responsible for bacterial turnover in soils that lead to many ecosystem services. The demonstrated breadth and specificity of bacterial host ranges for these predators make them interesting targets for the management of bacterial plant and human pathogens. However, there remain significant gaps in knowledge that will need to be filled in order to effectively utilize these predators for disease management. Here, we compared predatory strategies of the major groups of soil bacterial predators and outlined the gaps in knowledge or techniques that are limiting research. We offered specifi...
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Environmental Science & Technology, 2021
Micronutrients applied as nanoparticles of metal oxides have shown efficacy in vegetable and othe... more Micronutrients applied as nanoparticles of metal oxides have shown efficacy in vegetable and other crops for improving yield and reducing Fusarium diseases, but their role in ornamental crop management has not been investigated. In 2017, 2018, and 2020, nanoparticles of CuO, Mn2O3, or ZnO were foliarly applied at 500 μg/mL (0.6 mg/plant) to chrysanthemum transplants and planted in potting soil noninfested or infested with Fusarium oxysporum f. sp. chrysanthemi. An untreated control and a commercial fungicide, Fludioxonil, was also included. Chrysanthemums treated with nanoscale CuO had a 55, 30, and 32% reduction in disease severity ratings compared to untreated plants in 2017, 2018, and 2020, respectively. Specifically, the average dry biomass for the three years was reduced 22% by disease, but treatment with nanoscale CuO led to a 23% increase when compared to controls. Similar trends with plant height were observed. Horticultural quality was improved 28% with nano CuO and was equal to the fungicide. Nanoscale Mn2O3 and the fungicide did not consistently reduce disease ratings or increase dry biomass each year. Nanoscale ZnO was ineffective. Nanoscale CuO-treated plants had 24 to 48% more Cu/g tissue than controls (P < 0.001). These findings agree with past reports on food crops where single applications of nanoscale CuO improved plant health, growth, and yield and could offer significant impacts for managing plant diseases on ornamentals.
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GigaScience, 2019
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BackgroundRice molecular genetics, breeding, genetic diversity, and allied research (such as rice... more BackgroundRice molecular genetics, breeding, genetic diversity, and allied research (such as rice-pathogen interaction) have adopted sequencing technologies and high density genotyping platforms for genome variation analysis and gene discovery. Germplasm collections representing rice diversity, improved varieties and elite breeding materials are accessible through rice gene banks for use in research and breeding, with many having genome sequences and high density genotype data available. Combining phenotypic and genotypic information on these accessions enables genome-wide association analysis, which is driving quantitative trait loci (QTL) discovery and molecular marker development. Comparative sequence analyses across QTL regions facilitate the discovery of novel alleles. Analyses involving DNA sequences and large genotyping matrices for thousands of samples, however, pose a challenge to non-computer savvy rice researchers.FindingsWe adopted the Galaxy framework to build the feder...
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BackgroundLong-read sequencing facilitates assembly of complex genomic regions. In plants, loci c... more BackgroundLong-read sequencing facilitates assembly of complex genomic regions. In plants, loci containing nucleotide-binding, leucine-rich repeat (NLR) disease resistance genes are an important example of such regions. NLR genes make up one of the largest gene families in plants and are often clustered, evolving via duplication, contraction, and transposition. We recently mapped the Xo1 locus for resistance to bacterial blight and bacterial leaf streak, found in the American heirloom rice variety Carolina Gold Select, to a region that in the Nipponbare reference genome is rich in NLR genes.ResultsToward identification of the Xo1 gene, we combined Nanopore and Illumina reads to generate a high-quality genome assembly for Carolina Gold Select. We identified 529 full or partial NLR genes and discovered, relative to the reference, an expansion of NLR genes at the Xo1 locus. One NLR gene at Xo1 has high sequence similarity to the cloned, functionally similar Xa1 gene. Both harbor an int...
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Toxins, 2019
Toxin–antitoxin (TA) systems are diverse genetic modules with demonstrated roles in plasmid stabi... more Toxin–antitoxin (TA) systems are diverse genetic modules with demonstrated roles in plasmid stability, stress management, biofilm formation and antibiotic persistence. However, relatively little is known about their functional significance in plant pathogens. In this study we characterize type II and IV TA systems in the economically important plant pathogen Erwinia amylovora. Hidden Markov Model (HMM) and BLAST-based programs were used to predict the identity and distribution of putative TA systems among sequenced genomes of E. amylovora and other plant-associated Erwinia spp. Of six conserved TA systems tested for function from E. amylovora, three (CbtA/CbeA, ParE/RHH and Doc/PhD) were validated as functional. CbtA was toxic to E. amylovora, but not to Escherichia coli. While the E. coli homolog of CbtA elicits the formation of lemon-shaped cells upon overexpression and targets cytoskeletal proteins FtsZ and MreB, E. amylovora CbtA led to cell elongation and did not interact with ...
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Physiological and Molecular Plant Pathology, 2018
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Cell, 2017
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Phytopathology, May 23, 2017
Prevalence of Xanthomonas translucens, which causes cereal leaf streak (CLS) in cereal crops and ... more Prevalence of Xanthomonas translucens, which causes cereal leaf streak (CLS) in cereal crops and bacterial wilt in forage and turfgrass species, has increased in many regions in recent years. Because the pathogen is seedborne in economically important cereals, it is a concern for international and interstate germplasm exchange, and thus, reliable and robust protocols for its detection in seed are needed. However, historical confusion surrounding the taxonomy within the species has complicated the development of accurate and reliable diagnostic tools for X. translucens. Therefore, we sequenced genomes of 15 X. translucens strains representing six different pathovars and compared them with additional publicly available X. translucens genome sequences to obtain a genome-based phylogeny for robust classification of this species. Our results reveal three main clusters: one consisting of pathovar cerealis, one consisting of pathovars undulosa and translucens, and a third one consisting of...
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Frontiers in Plant Science, 2016
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Physiological and Molecular Plant Pathology, 2016
Abstract Transcriptional activator like (TAL) effectors are important virulence factors of severa... more Abstract Transcriptional activator like (TAL) effectors are important virulence factors of several plant pathogenic species of Xanthomonas. Members of this secreted protein family may activate transcription of; susceptibility factors, favoring disease, or resistance genes, triggering immunity. Accordingly, most research in this area has focused on the responses of a few model varieties of plants to the transcriptional activities of TAL effectors. However, a few studies suggest that plants may have evolved a diversity of additional responses to TAL effectors that are not well understood. These could include resistance to the effects of the TAL-activated susceptibility factors such as carbohydrate transporters, genomic multiplication of off-target effector binding sites, direct receptor recognition of the conserved TAL effector structure, or mutation of the host machinery required for TAL effector function. A better understanding of the diversity of plant responses to TAL effectors will be important for harnessing the potential of these proteins for agricultural applications.
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The Plant journal : for cell and molecular biology, Sep 20, 2016
The rice pathogens Xanthomonas oryzae pathovar (pv.) oryzae and pv. oryzicola produce numerous tr... more The rice pathogens Xanthomonas oryzae pathovar (pv.) oryzae and pv. oryzicola produce numerous transcription activator-like (TAL) effectors that increase bacterial virulence by activating expression of host susceptibility genes. Rice resistance mechanisms against TAL effectors include polymorphisms that prevent effector binding to susceptibility gene promoters, or that allow effector activation of resistance genes. This study identifies, in the heirloom variety Carolina Gold Select, a third mechanism of rice resistance involving TAL effectors. This resistance manifests through strong suppression of disease development in response to diverse TAL effectors from both X. oryzae pathovars. The resistance can be triggered by an effector with only 3.5 central repeats, is independent of the composition of the repeat variable diresidues that determine TAL effector binding specificity, and is independent of the transcriptional activation domain. We determined that the resistance is conferred ...
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Structure (London, England : 1993), Jan 2, 2015
Xanthomonas oryzae pv. oryzicola (Xoc) causes bacterial leaf streak (BLS) disease on rice plants.... more Xanthomonas oryzae pv. oryzicola (Xoc) causes bacterial leaf streak (BLS) disease on rice plants. Xoc delivers a type III effector AvrRxo1-ORF1 into rice plant cells that can be recognized by disease resistance (R) protein Rxo1, and triggers resistance to BLS disease. However, the mechanism and virulence role of AvrRxo1 is not known. In the genome of Xoc, AvrRxo1-ORF1 is adjacent to another gene AvrRxo1-ORF2, which was predicted to encode a molecular chaperone of AvrRxo1-ORF1. We report the co-purification and crystallization of the AvrRxo1-ORF1:AvrRxo1-ORF2 tetramer complex at 1.64 Å resolution. AvrRxo1-ORF1 has a T4 polynucleotide kinase domain, and expression of AvrRxo1-ORF1 suppresses bacterial growth in a manner dependent on the kinase motif. Although AvrRxo1-ORF2 binds AvrRxo1-ORF1, it is structurally different from typical effector-binding chaperones, in that it has a distinct fold containing a novel kinase-binding domain. AvrRxo1-ORF2 functions to suppress the bacteriostatic...
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Genomics of Plant-Associated Bacteria, 2014
ABSTRACT Xanthomonas oryzae pathovars oryzae and oryzicola cause bacterial leaf blight and bacter... more ABSTRACT Xanthomonas oryzae pathovars oryzae and oryzicola cause bacterial leaf blight and bacterial leaf streak of rice, respectively, two diseases that pose a significant threat to global rice yields. The first four complete genome sequences of X. oryzae strains yielded a wealth of information about virulence factor content, mobile genetic elements, and taxonomic differences among strains of X. oryzae pathovars oryzae and oryzicola. The genomes have been applied in systematic studies of gene function and expression and in comparative analyses of the differences between pathovars. X. oryzae genome sequences facilitated the current understanding of the evolutionary history and diversity of type III secreted effectors, including transcriptional activator-like (TAL) effectors, and contributed to the discovery of the code-mediating TAL effector recognition specificity. The genomes have also been instrumental in the development of improved tools for epidemiological typing and disease diagnostics. This chapter focuses on the contributions of genomic sequencing projects to the understanding of X. oryzae biology and diversity and the future questions that genomics will help address.
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Applied and environmental microbiology, 2014
Molecular diagnostics for crop diseases can enhance food security by enabling the rapid identific... more Molecular diagnostics for crop diseases can enhance food security by enabling the rapid identification of threatening pathogens and providing critical information for the deployment of disease management strategies. Loop-mediated isothermal amplification (LAMP) is a PCR-based tool that allows the rapid, highly specific amplification of target DNA sequences at a single temperature and is thus ideal for field-level diagnosis of plant diseases. We developed primers highly specific for two globally important rice pathogens, Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight (BB) disease, and X. oryzae pv. oryzicola, the causal agent of bacterial leaf streak disease (BLS), for use in reliable, sensitive LAMP assays. In addition to pathovar distinction, two assays that differentiate X. oryzae pv. oryzae by African or Asian lineage were developed. Using these LAMP primer sets, the presence of each pathogen was detected from DNA and bacterial cells, as well as leaf and seed...
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Antonie van Leeuwenhoek, 2015
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Annual Review of Phytopathology, 2014
Rice feeds more than half of the world's population. Rice blast, caused by the fungal pathoge... more Rice feeds more than half of the world's population. Rice blast, caused by the fungal pathogen Magnaporthe oryzae, and bacterial blight, caused by the bacterial pathogen Xanthomonas oryzae pv. oryzae, are major constraints to rice production worldwide. Genome sequencing and extensive molecular analysis has led to the identification of many new pathogen-associated molecular patterns (PAMPs) and avirulence and virulence effectors in both pathogens, as well as effector targets and receptors in the rice host. Characterization of these effectors, host targets, and resistance genes has provided new insight into innate immunity in plants. Some of the new findings, such as the binding activity of X. oryzae transcriptional activator–like (TAL) effectors to specific rice genomic sequences, are being used for the development of effective disease control methods and genome modification tools. This review summarizes the recent progress toward understanding the recognition and signaling event...
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Research in Microbiology, 2010
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Plant Disease, 2014
The vast amount of data available through next-generation sequencing technology is facilitating t... more The vast amount of data available through next-generation sequencing technology is facilitating the design of diagnostic marker systems. This study reports the use of draft genome sequences from the bacterial plant pathogen Pseudomonas fuscovaginae, the cause of sheath brown rot of rice, to describe the genetic diversity within a worldwide collection of strains representing the species. Based on a comparative analysis with the draft sequences, primers for a loop-mediated isothermal amplification (LAMP) assay were developed to identify P. fuscovaginae. The assay reported here reliably differentiated strains of P. fuscovaginae isolated from rice from a range of other bacteria that are commonly isolated from rice and other plants using a primer combination designated Pf8. The LAMP assay identified P. fuscovaginae purified DNA, live or heat-killed cells from pure cultures, and detected the bacterium in extracts or exudates from infected host plant material. The P. fuscovaginae LAMP assa...
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Phytopathology®, 2014
Seed sterility and grain discoloration limit rice production in Colombia and several Central Amer... more Seed sterility and grain discoloration limit rice production in Colombia and several Central American countries. In samples of discolored rice seed grown in Colombian fields, the species Burkholderia glumae and B. gladioli were isolated, and field isolates were compared phenotypically. An artificial inoculation assay was used to determine that, although both bacterial species cause symptoms on rice grains, B. glumae is a more aggressive pathogen, causing yield reduction and higher levels of grain sterility. To identify putative virulence genes differing between B. glumae and B. gladioli, four previously sequenced genomes of Asian and U.S. strains of the two pathogens were compared with each other and with two draft genomes of Colombian B. glumae and B. gladioli isolates generated for this study. Whereas previously characterized Burkholderia virulence factors are highly conserved between the two species, B. glumae and B. gladioli strains are predicted to encode distinct groups of gen...
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Papers by Lindsay Triplett