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Madison, WI, United States

Bethke P.C.,Vegetable Crops Research Unit | Bethke P.C.,University of Wisconsin - Madison | Busse J.S.,Vegetable Crops Research Unit
American Journal of Potato Research | Year: 2010

The quality of potato (Solanum tuberosum) tubers coming out of storage depends on the state of the tubers going into storage. Experiments determined the effects of vine-kill treatment and harvest date on the post-harvest physiology of potato tubers stored for up to 12 weeks. Potato cultivar Russet Burbank grown in central Wisconsin was harvested in late July when tubers were immature, in late August, and in early September after complete natural senescence of vines. Prior to the first two harvests, vines were either desiccated with diquat dibromide or were untreated. Data were collected at harvest and in storage for skin set, tuber respiration rate, and tuber sucrose, glucose, and fructose contents. Skin set at harvest was increased by use of the desiccant at the early harvest date, but not at the middle harvest date. Early harvest without vine kill resulted in elevated tuber bud-end glucose contents in storage. Early harvest with vine kill treatment resulted in increased rates of respiration in storage that persisted through December. Neither tuber sucrose nor glucose content 6 weeks after harvest was a good predictor of tuber glucose content 12 weeks after harvest. These data demonstrate that vine-kill treatment and tuber maturity at harvest have long-term effects on tuber quality. © 2010 Potato Association of America.

Hogan C.S.,University of Wisconsin - Madison | Mole B.M.,University of North Carolina at Chapel Hill | Grant S.R.,University of North Carolina at Chapel Hill | Willis D.K.,University of Wisconsin - Madison | And 2 more authors.
PLoS ONE | Year: 2013

Pectobacterium species are enterobacterial plant-pathogens that cause soft rot disease in diverse plant species. Unlike hemi-biotrophic plant pathogenic bacteria, the type III secretion system (T3SS) of Pectobacterium carotovorum subsp. carotovorum (P. carotovorum) appears to secrete only one effector protein, DspE. Previously, we found that the T3SS regulator HrpL and the effector DspE are required for P. carotovorum pathogenesis on leaves. Here, we identified genes up-regulated by HrpL, visualized expression of dspE in leaves, and established that DspE causes host cell death. DspE required its full length and WxxxE-like motifs, which are characteristic of the AvrE-family effectors, for host cell death. We also examined expression in plant leaves and showed that hrpL is required for the expression of dspE and hrpN, and that the loss of a functional T3SS had unexpected effects on expression of other genes during leaf infection. These data support a model where P. carotovorum uses the T3SS early in leaf infection to initiate pathogenesis through elicitation of DspE-mediated host cell death.

Hao L.-Y.,University of Wisconsin - Madison | Willis D.K.,University of Wisconsin - Madison | Willis D.K.,Vegetable Crops Research Unit | Andrews-Polymenis H.,Texas A&M University | And 3 more authors.
Applied and Environmental Microbiology | Year: 2012

Contaminated fresh produce has become the number one vector of nontyphoidal salmonellosis to humans. However, Salmonella enterica genes essential for the life cycle of the organism outside the mammalian host are for the most part unknown. Screening deletion mutants led to the discovery that an aroA mutant had a significant root colonization defect due to a failure to replicate. AroA is part of the chorismic acid biosynthesis pathway, a central metabolic node involved in aromatic amino acid and siderophore production. Addition of tryptophan or phenylalanine to alfalfa root exudates did not restore aroA mutant replication. However, addition of ferrous sulfate restored replication of the aroA mutant, as well as alfalfa colonization. Tryptophan and phenylalanine auxotrophs had minor plant colonization defects, suggesting that suboptimal concentrations of these amino acids in root exudates were not major limiting factors for Salmonella replication. An entB mutant defective in siderophore biosynthesis had colonization and growth defects similar to those of the aroA mutant, and the defective phenotype was complemented by the addition of ferrous sulfate. Biosynthetic genes of each Salmonella siderophore, enterobactin and salmochelin, were upregulated in alfalfa root exudates, yet only enterobactin was sufficient for plant survival and persistence. Similar results in lettuce leaves indicate that siderophore biosynthesis is a widespread or perhaps universal plant colonization fitness factor for Salmonella, unlike phytobacterial pathogens, such as Pseudomonas and Xanthomonas. © 2012, American Society for Microbiology.

Vinje M.A.,University of Wisconsin - Madison | Vinje M.A.,Cereal Crops Research Unit | Willis D.K.,University of Wisconsin - Madison | Willis D.K.,Vegetable Crops Research Unit | And 3 more authors.
Planta | Year: 2011

Two barley (Hordeum vulgare L.) β-amylase genes (Bmy1 and Bmy2) were studied during the late maturation phase of grain development in four genotypes. The Bmy1 and Bmy2 DNA and amino acid sequences are extremely similar. The largest sequence differences are in the introns, seventh exon, and 3′ UTR. Accumulation of Bmy2 mRNA was examined in developing grain at 17, 19, and 21 days after anthesis (DAA). One genotype, PI 296897, had significantly higher Bmy2 RNA transcript accumulation than the other three genotypes at all developmental stages. All four genotypes had Bmy2 mRNA levels decrease from 17 to 19 DAA, and remain the same from 19 to 21 DAA. Levels of Bmy1 mRNA were twenty thousand to over one hundred thousand times more than Bmy2 mRNA levels in genotypes Legacy, Harrington, and Ashqelon at all developmental stages and PI 296897 at 19 and 21 DAA. PI 296897 had five thousand times more Bmy1 mRNA than Bmy2 mRNA at 17 DAA. However, Bmy2 protein was not found at 17 DAA in any genotype. The presence of Bmy2 was immunologically detected at 19 DAA and was present in greater amounts at 21 DAA. Also, Bmy2 protein was found to be stored in mature grain and localized in the soluble fraction. However, Bmy1 protein was far more prevalent than Bmy2 at all developmental stages in all genotypes. Thus, the vast majority of β-amylase activity in developing and mature grain can be attributed to endosperm-specific β-amylase. © 2011 Springer-Verlag (outside the USA).

del Pilar Marquez-Villavicencio M.,University of Wisconsin - Madison | Weber B.,University of Wisconsin - Madison | Witherell R.A.,University of Wisconsin - Madison | Willis D.K.,University of Wisconsin - Madison | And 2 more authors.
PLoS ONE | Year: 2011

Pectobacterium species are necrotrophic bacterial pathogens that cause soft rot diseases in potatoes and several other crops worldwide. Gene expression data identified Pectobacterium carotovorum subsp. carotovorum budB, which encodes the α-acetolactate synthase enzyme in the 2,3-butanediol pathway, as more highly expressed in potato tubers than potato stems. This pathway is of interest because volatiles produced by the 2,3-butanediol pathway have been shown to act as plant growth promoting molecules, insect attractants, and, in other bacterial species, affect virulence and fitness. Disruption of the 2,3-butanediol pathway reduced virulence of P. c. subsp. carotovorum WPP14 on potato tubers and impaired alkalinization of growth medium and potato tubers under anaerobic conditions. Alkalinization of the milieu via this pathway may aid in plant cell maceration since Pectobacterium pectate lyases are most active at alkaline pH.

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