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Plant Biology Research Profiles

Researcher: Nick Carpita

Figure 1:  Mixed-linkage (1→3),(1→4)-ß-D-glucans are unbranched cell-wall polymers composed of cellotriosyl, cellotetraosyl, and smaller amounts of higher cellodextrins connected by single (1→3)-ß- linkages These polymers are only found in grasses and closely related species, and are found at only specific times during development They are the causal agents in the ability of some cereal brans, such as oat and barley, to lower serum cholesterol in humans and insulin demand by diabetics. Click image to enlarge	Figure 2:  The mixed-linkage ß-glucans are made in the Golgi apparatus, packaged into secretory vesicles, and transported to the cell surface where they are tightly integrated into the cellulosic network We have optimized flotation centrifugation in sucrose gradients for convenient and rapid isolation of maize Golgi for synthesis of ß-glucans in vitro with radiolabeled substrate Oligomers diagnostic of ß-glucan are generated by a special enzyme, and separated by HPLC, and quantified by an electrochemical detector. Click image to enlarge
Figure 3:  From data described in detail in Urbanowicz et al. (2004), we propose that the mixed-linkage ß-glucan synthase complex is the topologic equivalent of cellulose synthase It consists of a core synthase forming a channel in the Golgi membrane and an extrinsic glucosyl transferase that is equally necessary for synthesis, which is located on the cytoplasmic side of the membrane As the polymer is made, it is extruded into the lumen of the Golgi. Click image to enlarge	Figure 4:  In collaboration with Dr. Steve Scofield in Agronomy, Dr. Mick Held, a post-doctoral associate in the Carpita lab, is currently using viral-induced gene silencing, or “VIGS”, to identify the genes encoding the core synthase.

Links:

Nick Carpita Faculty Page

Publications:

• Urbanowicz, B. R., C. Rayon, N. C. Carpita 2004. Topology of the maize mixed-linkage (1→3),(1→4)-ß-D-glucan synthase at the Golgi membrane.  Plant Physiol. 134, 758–768.
• Buckeridge, M. S., C. Rayon, B. Urbanowicz, M. A. S. Tine, N. C. Carpita 2004. Mixed linkage (1→3),(1→4)-ß-D-glucans of grasses Cereal Chem.81, 115-127.
• Carpita, N. C., M. Defernez, K. Findlay, B. Wells, D. A. Shoue, G. Catchpole, R. H. Wilson, and M. C. McCann 2001. Cell wall architecture of the elongating maize coleoptile Plant Physiol127, 551-565.
• Carpita, N., M. Tierney, and M. Campbell 2001. Molecular biology of the plant cell wall:  Searching for the genes that define structure, architecture and wall dynamics Plant Mol. Biol. 47, 1-5.
• Vergara, C. E., N. C. Carpita 2001 ß-D-Glycan synthases and the CesA gene family:  Lessons to be learned from themixed-linkage (1→3),(1→4)ß-D-glucan synthase.Plant Mol. Biol.47, 145-160.
• Buckeridge, M. S., C. E. Vergara, and N. C. Carpita 2001 Insight into multi-site mechanisms of glycosyl transfer in (1→4)ß-D-glycans provided by the cereal mixed-linkage (1→3),1→4)ß-D-glucan synthase. Phytochemistry 57, 1045-1053. [
• Kim, J-B., A. T. Olek, and N. C. Carpita 2000 Cell-wall and membrane-associated exo-ß-D-glucanases from developing maize seedlings Plant Physiol.123, 471-485.
• Buckeridge, M. S., C. E. Vergara, and N. C. Carpita 1999 Mechanism of synthesis of a cereal mixed-linkage (1→3),(1→4)ß-D-glucan:  Evidence for multiple sites of glucosyl transfer in the synthase complex Plant Physiol.120, 1105-1116.

Insertion of CYP86B1 into chloroplastic membranes is both specific and sensitive to protease digestion. [35S]-Labeled- (a) CYP86B1, (b) CYP73A5 (an ER localized protein) and (c) pSS were incubated with pea chloroplasts in the absence of ATP (a) or in the presence of 4 mM ATP (b and c) for 30 min. After import, chloroplasts were incubated with (+) or without (-) Thermolysin (Th.) for 30 min at 4°C in the dark. Protease reactions were quenched with EDTA and chloroplast fractions were isolated and analyzed.

Links:

Ron Coolbaugh Faculty Page

Midwest Cytochrome P450 Symposium

Publications:

• Jennings, J.C. J.A. Banks, and R.C. Coolbaugh. 1996. Subtractive hybridization between cDNAs from untreated and AMO-1618-treated cultures of Gibberella fujikuroi. Plant and Cell Physiol. 37: 847-854.
• Watson, Christy, John Froehlich, Caroline Josefsson, Clint Chapple, Francis Durst, Irene Benveniste, and Ronald Coolbaugh. 2001. Localization of CYP86B1 in the outer envelope of chloroplasts. Plant and Cell Physiology. 42:873-878.

Collaboration/Grants:

Ralph Nicholson, Plant Pathology, Purdue Philippe Urban, CNRS, France

Barry Pittendrigh, Entomology, Purdue John Froehlich, PRL, Michigan State

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Plant Pathology Research Profiles

Researcher: Larry Dunkle
Description: A gene previously unknown in fungi was discovered among a group of regulatory genes whose expression is increased during the formation of conidia (asexual spores) by Setosphaeria turcica, the fungal pathogen causing northern leaf blight of corn. This gene, designated StCRY1, corresponds to a cryptochrome-type photoreceptor known to mediate blue-light responses in plants and animals, including human. Cryptochromes are photolyase-like blue-light receptors containing flavin and pterin chromophores, but no photolyase or other biochemical activity has been demonstrated for a cryptochrome. In plants, cryptochromes, often interacting with phytochrome or phototropin, regulate photomorphogenesis and light-induced gene expression. In animals, cryptochromes function in the entrainment of the circadian clock by physically interacting with central oscillator components. No cryptochrome-like genes have been examined to date in any other fungus, but a phylogenetic analysis of genes with substantial sequence similarity to StCRY1 indicates that CRY1 homologues exist in the genomes of plant pathogenic fungi but not in the genomes of saprophytic fungi. Expression of StCRY1 in S. turcica is repressed by light but rapidly induced to high levels in darkness, which is required for completion of conidiation in this fungal pathogen. The functional characterization of fungal cryptochromes likely will reveal interesting and important roles of this class of photoreceptors in plant pathogenesis as well as fungal morphogenesis. We are testing our hypothesis that the cryptochrome gene product is a blue-light receptor that regulates conidiation and influences development and virulence in S. turcica, Magnaporthe grisea (the rice blast fungus), and Fusarium graminearum (the wheat scab fungus) by gene disruption and analyses of the mutant phenotypes.

Lesions of northern corn leaf blight and a conidium produced by the fungal pathogen Setosphaeria turcica (top). Cultures incubated in continuous light are arrested after production of conidiophores but produce conidia when transferred to darkness (bottom). Images on the right side are a ribbon diagram and a tertiary model of a plant cryptochrome (from Lin and Shatlin, 2003).

Links:

Larry Dunkle Faculty Page

Publications:

• Flaherty, J.E. and L.D. Dunkle. 2005. Identification and expression analysis of signal transduction genes induced during conidiation in Exserohilum turcicum. Fungal Genet. Biol. 42: 471-481.

Assistantships:

Are not available with this researcher.

• Investigation of the overwintering capacity of Magnaporthe grisea, the causal agent of gray leaf spot of perennial ryegrass. The objective of this research is to understand the influence of environmental conditions on the overwinter survival of the pathogen so that we will be able to accurately assess the threat of disease epidemics during summer months.
• Evaluations of the sensitivity of populations of Sclerotinia homoeocarpa to fungicides. Golf course superintendents rely on fungicides to control dollar spot (caused by S. homoeocarpa). After a period of use, fungal populations may lose some or all of their sensitivity to the fungicide, resulting in unacceptable levels of disease. The objective of this research is to define the levels of sensitivity in S. homoeocarpa isolates across Indiana, and help superintendents make informed decisions about fungicides for dollar spot control.
• Investigation of the influence of environmental parameters on brown patch of creeping bentgrass. Brown patch develops during warm nights with long dew periods. The objective of this research is to more accurately define the conditions that promote brown patch establishment and spread. Once those factors are defined, turf managers will be better able to anticipate disease outbreaks and make timely sprays to avoid serious turf damage.

Gray leaf spot lesions on perennial ryegrass	Dollar spot management research plots	Brown patch symptoms on creeping bentgrass

Links:

Richard Latin Faculty Page

Turfgrass Disease Profiles

Publications:

• Harmon, P. F., and Latin, R. 2005.  Winter survival of the perennial ryegrass pathogen Magnaporthe oryzae in north central Indiana.   Plant Disease 89:412-418.
• Latin, R.  2005.  Managing take all patch of creeping bentgrass on sand-based greens. Golf Course Management 73:2:101-105.
• Hardebeck, G. A., Reicher, Z. J., Turco, R. F., and Latin, R. 2004.  Application of Pseudomonas aureofaciens strain Tx-1 for control of dollar spot and brown patch on fair height turfgrass.  HortSci. 39:1750-1753.
• Latin, R. and Harmon, P. 2004.  Managing gray leaf spot in the Midwest. Golf Course Management 72:10:89-92.
• Latin, R. 2004.  New turfgrass diseases.  Grounds Maintenance. V3: 25-31. 
• Harmon, P. F. and Latin, R. 2003. Gray Leaf Spot of Perennial Ryegrass. Online. Plant Health Progress doi:10.1094/PHP-2003-12XX-01-D
• Harmon, P. F., Dunkle, L. D., and Latin R. 2003. A rapid PCR-based method for the detection of Magnaporthe oryzae from infected perennial ryegrass. Plant Dis. 87:1072-1076.
• Harmon, P.F., Rane, K.K., Ruhl, G.E., and Latin, R. 2000. First report of gray leaf spot on perennial ryegrass in Indiana. Plant Disease 84: 492.
• Gross, M.K., Santini, J., Tikhonova, I., and Latin, R. 1998. The influence of temperature and leaf wetness duration on infection of perennial ryegrass by Rhizoctonia solani. Plant Dis. 82: 1012-1016.

Assistantships:

A graduate research assistantship is available at the M.S. or Ph.D. level. Contact Dr. Richard Latin about this opportunity.

Collaboration/Grants:

Golf Course Superintendents Association of America Midwest Regional Turf Foundation

Dr. Zac Reicher, Agronomy, Purdue University Dr. Tim Gibb, Entomology, Purdue University Dr. Lee Burpee, Plant Pathology, University of Georgia

Researcher : Guri Johal
Description: Dr. Johal’s research expertise is in maize genetics and pathology and he uses a combination of genetic, genomic and molecular approaches to investigate how maize plants grow and cope with stresses imposed by an ever-changing environment. His long-term aspirations are to generate biological tools and knowledge that may be used to produce crops in a beneficial yet environmentally friendly and sustainable manner. Presently, the Johal lab is engaged in two distinct but overlapping areas of research in maize pathology.

The first concerns the maize leaf blight and ear rot disease caused by race 1 of Cochliobolus carbonum, a fungal pathogen that employs a host-selective toxin (HC-toxin) to accomplish host infection. Dr. Johal’s research on this pathosystem has led to some major milestones in the discipline of plant pathology. These include: the first ever cloning of a disease resistance gene in plants, elucidation that this resistance gene (called Hm1) provides protection by inactivating HC-toxin, and the revelation of genetic and molecular events that led to the genesis of the leaf blight and ear rot disease. Current research on this pathosystem seeks to elucidate the mechanism(s) by which HC-toxin facilitates colonization of maize tissues by C. carbonum race 1.

Leaf blight and ear mold disease of maize caused by C. carbonum race 1. Plants on the left were pictured at the time of inoculation. Same plants are shown on the right three weeks later.

Johal’s second area of research involves mutants that form disease-like symptoms in the absence of pathogens. Called disease lesion mimics, these mutants are proving to be excellent tools for unraveling how plants cope with diverse stresses and how programmed death of cells is regulated and executed in plants. Johal was one of the first to recognize this potential of lesion mimic mutants, and he has contributed enormously to advance this area. Thus far his group has cloned three lesion mimic genes, with many more in the pipeline for isolation and characterization.

More than 50 disease lesion mimic mutants have been isolated in maize. Shown here are Les10 (A), les2014 (B), lls1 (C), and Les9 (D).

Links:

Guri Johal Faculty Page

Publications:

• Penning, B.W., G.S. Johal and M.M. McMullen. 2004. A major suppressor of cell death, slm1, modifies the expression of the maize (Zea mays L.) lesion mimic mutation les23. Genome 47: 961-969.
• Multani, D.S., S.P. Briggs, M.A. Chamberlin, J.J. Blakeslee, A.S. Murphy, and G.S. Johal. 2003. Loss of an MDR transporter in compact stalks of maize br2 and sorghum dw3 mutants. Science 302: 81-4.
  Links to Abstract or Full Text
• Gray, J., P.S. Close, S.P. Briggs and G.S. Johal. 1997. A novel suppressor of cell death in plants encoded by the Lls1 gene of maize. Cell 89: 25-31.
• Johal, G.S. and S.P. Briggs. 1992. Reductase activity encoded by the HM1 disease resistance gene in maize. Science 258: 985-987.

Assistantships:

Are not currently available with this researcher.

Another of Shaner's research areas is partial resistance of wheat and oat to rust fungi. This resistance appears to be more durable than hypersensitive resistance. Shaner has characterized this resistance phenotypically and genetically, and has investigated its ability to retard development of rust in the field. He has also investigated the ability of the wheat leaf rust fungus to overcome partial resistance.

Shaner also evaluates the efficacy of fungicides for control of leaf diseases of seed corn. Seed corn production is a major industry in Indiana. Many inbreds are susceptible to foliar diseases. Fungicides can provide effective and economical control of these diseases. Field trials are designed to compare various application schedules and products for their ability to reduce severity of disease and improve yield and seed quality.

Wheat heads 16 days after point inoculation with Fusarium graminearum. Left: Resistant plant. Right: susceptible plant.	Different reactions of the same cultivar according to method of inoculation. Left: Entire head is blighted after spores of F. graminearum are sprayed onto entire head. Right: Almost no blight develops when spores are  placed only in a single floret (point inoculation).	Point inoculation of a wheat head with spores of Fusarium graminearum. A 15 µl drop of spore suspension is placed in one upper floret.

Links:

Gregory Shaner Faculty Page

Publications:

• Bai, G., Kolb, F., Shaner, G., Domier, L. 1999. Amplified fragment length polymorphism markers linked to a major quantitative trait locus controlling scab resistance in wheat. Phytopathology 89:343-348.
• Bai, G.-H., Shaner, G., Ohm, H. 2000. Inheritance of resistance to Fusarium graminearum in wheat. Theor. Appl. Genet. 100:1-8.
• Bai, G-H, Shaner, G. 1996. Variation in Fusarium graminearum and cultivar resistance to wheat scab. Plant Dis. 80:975-979.
• Desjardins, A. E., Proctor, R. H., Bai, G., McCormick, S. P., Shaner, G. Buechley, G., Hohn, T. H. 1996. Reduced virulence of trichothecene-nonproducing mutants of Gibberella zeae in wheat field tests. Molec. Plant-Microbe Interactions 9:775-781.
• Francl, L., Shaner, G., Bergstrom, G. Gilbert, J., Pedersen, W., Dill-Macky, R., Sweets, L., Corwin, B., Jin, Y., Dallenberg, D., Wiersma, J. 1999. Daily inoculum levels of Gibberella zeae on wheat spikes. Plant Dis. 83:662-666.
• Shaner, G., Buechley, G., Nyquist, W. E. 1997. Inheritance of latent period of Puccinia recondita in wheat. Crop Sci. 37:748-756.

Assistantships:

Are available with this researcher.

Researcher : Ralph Nicholson
Description: Research involves identifying the compounds made by sorghum and corn that protect these plants from disease. In sorghum, resistance compounds are deoxyanthocyanidins. They function as phytoalexins. Because they are colored, they are "easy" to work with and provide a significant tool for learning about how the plant protects itself from fungal pathogens. In corn, the compounds are phenylpropanoid phenols. All of these compounds have been shown to be toxic to fungi.

Other research involves learning how fungi "stick" to plants. If a fungus cannot stick, then disease cannot occur. Colletotrichum graminicola spores stick to leaves within minutes of contact. The same thing happens with the sorghum anthracnose fungus, Colletotrichum sublineolum. Importantly, spores only stick if the leaf surface is very hydrophobic. Another pathogen we work with is the fungus, Blumeria graminis that causes powdery mildew of barley. With each of these fungi we are trying to understand how the extracellular matrix is released. Collaborative work has led to the discovery that some of the components of the matrix function as "messengers" in signal transduction. We seek to determine if plants with less hydrophobic leaves can serve as tools for resistance. We have started to learn what the adhesive molecules are and when they are produced by various fungal pathogens.

Conidia of Colletotrichum graminicola stained with neutral red to measure conidial survival when stored for up to 80 days in a "moist" environment.

Links:

Ralph Nicholson Faculty Page

Publications:

• Boddu J, Svabek C, Sekhon R, Gevens A, Nicholson RL, Jones AD, Pedersen JF, Gustine DL, Chopra S. 2005. Expression of a putative flavonoid 3’ hydroxylase in sorghum mesocotyls synthesizing 3-deoxyanbthocyanidins. Physiological and Molecular Plant Pathology. 65:101-113
• Nielsen KA, Gotfredsen CH, Buch-Pedersen MJ. AmmitzbØll H, Mattsson O, Duus JØ, Nicholson RL. 2004 Physiological and Molecular Plant Pathology 65:167-196.
• Wharton, P and Nicholson, RL. 2000. Temporal synthesis and radiolabelling of the sorghum 3-deoxyanthocyanidin phytoalexins and the anthocyanin 3-dimalonyl glucoside. New Phytologist 145:457-469
• Nielsen, KA, Nicholson, RL., Carver TLW, Kunoh H, and Oliver, R.P. 2000 First touch: An immediate  response  to surface recognition in conidia of Blumeria graminis Physiological and Molecular Plant Pathologhy 56:63-70.
• Deising, H., Nicholson, R.L., Haug, M., Howard, R.J., and Mendgen, K. 1992 Adhesion pad formation and the involvement of surface localized  cutinase and esterases in the attachment of Uredospores  to the host cuticle The Plant Cell 4:1011-1111.
• Snyder, B.A., and Nicholson, R.L. 1990 Synthesis of Phytoalexins  in Sorghum as a Site Specific Response to Fungal Ingress Science 248:1637-1639.

Assistantships:

Are currently not available with this researcher.

Collaboration/Grants:

• Dr. Hitoshi Kunoh at Mie University (Tsu, Japan)
• Dr. Kirsten Nielsen at the Royal Veterinary and Agriculture University (Copenhagen, Denmark)
• Dr. Timothy Carver (Aberystwyth, Wales)
• National Science Foundation grant

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Weed Science Research Profiles

Links:

Carole Lembi Faculty Page

"Why Aquatic Herbicides Affect Aquatic Plants and Not You"

Cylindrospermopsis and Pseudanabaena

Publications:

• Lembi, C. A. 2000. Relative tolerance of mat-forming algae to copper. J. Aquat. Plant Manage. 38:68-70.
• Berry, H. A. and C. A. Lembi. 2000. Effects of temperature and irradiance on the seasonal variation of a Spirogyra (Chlorophyta) population in a midwestern lake (U.S.A.). J. Phycol. 36: 841-851.
• Glomski, L.A., K.V. Wood, R.L. Nicholson, and C.A. Lembi. 2002. The search for exudates from Eurasian watermilfoil and hydrilla. J. Aquatic Plant Management 40:17-22.

Acknowledgments:

Many thanks to Debra Lubelski, our laboratory technician, for her help and dedication.

Collaboration/Grants:

H. Lynn Walker, Louisiana Tech University

Ralph Nicholson , Botany & Plant Pathology, Purdue

The second area my program is working involves interactions between winter annual weeds and soybean cyst nematode Soybean cyst nematode (SCN) is a viable threat to profitable soybean production in the Indiana and the entire Midwest. Winter annual weed populations in production fields have been increasing due to the widespread adoption of conservation tillage practices and reduced reliance on herbicides with soil residual activity. Among the many negative impacts of winter annual weeds is that a number of these species can serve as alternate hosts for SCN. Current integrated pest management systems for SCN include rotation to a non-host crop and use of SCN resistant soybean varieties. However, these management recommendations may be inadequate if SCN is able to reproduce on winter annual weeds when soybean is not present My group  has initiated studies to evaluate the long-term impact of winter weed management tactics on SCN populations and we are attempting to more closely document the reproductive capability of SCN on alternative hosts such as purple deadnettle.

The third area we are investigating involves giant ragweed interference in corn, control of insect infested plants, and determining the predominate insect species found in giant ragweed during the growing season.Giant ragweed is poorly controlled by all soil-applied herbicides currently labeled in corn and soybean. Giant ragweed also serves as a host for a number of stalk boring insects including the common stalk borer and European corn borer. Control of insect-infested plants with postemergence herbicides such as glyphosate is occasionally compromised It is well known that corn is sensitive to early-season weed competition, however, broadleaf weed interference and its impact on nitrogen accumulation is poorly understood at the current time My group is conducting both field and greenhouse studies to address the impact of low densities of giant ragweed on nitrogen accumulation and corn yield, and to gain a greater understanding about the interactions between insect infestations and postemergence herbicide activity.

Links:

Bill Johnson Faculty Page

Purdue Weed Science Page

Purdue Horseweed Page

Annual Integrated Weed Management Research Report

Publications:

• Creech*, J.E., W. G. Johnson, J. Faghihi, V. Ferris, and A. Westphal. 2005. First report of soybean cyst nematode reproduction on purple deadnettle under field conditions. Online. Crop Management doi. (in press).
• Gibson*, K.D., W.G. Johnson, and D. Hilger. 2005. Farmer perceptions of problematic corn and soybean weeds in Indiana. Weed Technol. (in press).
• Johnson*, B., J. Barnes, K. Gibson, and S. Weller. 2004. Late season weed escapes in Indiana soybean fields. Online. Crop Management doi:10.1094/CM-2004-0923-01-BR.
• Barnes, J., B. Johnson*,  K. Gibson, and S. Weller. 2004. Crop rotation and tillage system influence late-season incidence of giant ragweed and horseweed in Indiana soybean. Online. Crop Management doi:10.1094/CM-2004-0923-02-BR.

Acknowledgements:

Many thanks are expressed to the graduate students and AP staff who have made major contributions to this research program. These individuals include Earl Creech, Vince Davis, Reece Dewell, Glenn Nice, and Eric Ott.

Assistantships:

Are not available with this researcher at the current time.

Collaboration/Grants:

Rhamnus frangula	Garlic Mustard (Alliaria petiolata)

Links:

Kevin Gibson Faculty Page

Publications: See faculty page for recent publications.

Assistantships:

Are available with this researcher.

	Figure 1. Clone ALT1 from Altamont, IL shows significant levels of resistance. Plants treated with glyphosate concentrations significantly higher than the recommended rate (1X = 0.63 kg ae/ha) were not killed. Plants treated with the recommended rate were only slightly stunted. In comparison, most clones tested ("susceptible clones") were killed or severely stunted by the recommended rate (not shown).
Kathy Anderson has been evaluating the bioherbicide potential of the fungus Myrothecium verrucaria. She has shown that the fungus is highly effective for the control of a wide range of important weed species (Figure 2). The fungus causes damage to these weeds primarily by releasing phytotoxins into its culture medium. It is these toxins in the culture medium that control the weeds when sprayed, not infection by the fungus per se (Figure 3).
Figure 2. Impact of crude filtrates of Myrothecium verrucaria on selected weeds. LEFT: Control, RIGHT: Treated. Species top-to-bottom and left-to-right: Chenopodium album, Amaranthus tuberculatus, Xanthium strumarium, Abutilon theophrasti, Sesbania exaltata, Solanum ptycanthum, Sida spinosa, Digitaria sanguinalis, Cyperus esculentus.
	Figure 3. Effect of foliar application of different spore concentrations and filtrate concentrations from cultures of Myrothecium verrucaria upon dry weights of common lambsquarters (Chenopodium album).

Links:

For more information and related research, visit Steve Hallett's Faculty Page

Publications: See faculty page for recent publications.

Assistantships:

Are available with this researcher.