Diane E. Ullman

Bio: Diane E. Ullman is an academic researcher from University of California, Davis. The author has contributed to research in topics: Thrips & Western flower thrips. The author has an hindex of 36, co-authored 92 publications receiving 4823 citations. Previous affiliations of Diane E. Ullman include University of Hawaii & University of Hawaii at Manoa.

The nematode resistance gene Mi of tomato confers resistance against the potato aphid

Abstract: Resistance against the aphid Macrosiphum euphorbiae previously was observed in tomato and attributed to a novel gene, designated Meu-1, tightly linked to the nematode resistance gene, Mi. Recent cloning of Mi allowed us to determine whether Meu-1 and Mi are the same gene. We show that Mi is expressed in leaves, that aphid resistance is isolate-specific, and that susceptible tomato transformed with Mi is resistant to the same aphid isolates as the original resistant lines. We conclude that Mi and Meu-1 are the same gene and that Mi mediates resistance against both aphids and nematodes, organisms belonging to different phyla. Mi is the first example of a plant resistance gene active against two such distantly related organisms. Furthermore, it is the first isolate-specific insect resistance gene to be cloned and belongs to the nucleotide-binding, leucine-rich repeat family of resistance genes.

Tospoviruses: diagnosis, molecular biology, phylogeny, and vector relationships.

Abstract: The disease known as "spotted wilt" was first described in Australia in 1 9 1 5 ( 16) and shown to have a viral etiology b y Samuel et al i n 1930 ( 14 1 ). Since that time, viruses similar or identical to the tomato spotted wilt virus (TSWV) have been the cause of plant diseases epidemics in tropical, subtropical, and temperate regions throughout the Northern hemisphere, Western Europe, and Asia (2, 7, 19 , 29, 30, 55, 56, 78, 80, 105 , 108, 1 5 1 , 1 53 , 170). Major economic losses are due in large part to an extremely wide host range involving more than 500 species of plants in more than 50 families that

Infection with a plant virus modifies vector feeding behavior.

Abstract: Vector infection by some animal-infecting parasites results in altered feeding that enhances transmission. Modification of vector behavior is of broad adaptive significance, as parasite fitness relies on passage to a new host, and vector feeding is nearly always essential for transmission. Although several plant viruses infect their insect vectors, we have shown that vector infection by a plant virus alters feeding behavior. Here we show that infection with Tomato spotted wilt virus (TSWV), type member of the only plant-infecting genus in the Bunyaviridae, alters the feeding behavior of its thrips vector, Frankliniella occidentalis (Pergande). Male thrips infected with TSWV fed more than uninfected males, with the frequency of all feeding behaviors increasing by up to threefold, thus increasing the probability of virus inoculation. Importantly, infected males made almost three times more noningestion probes (probes in which they salivate, but leave cells largely undamaged) compared with uninfected males. A functional cell is requisite for TSWV infection and cell-to-cell movement; thus, this behavior is most likely to establish virus infection. Some animal-infecting members of the Bunyaviridae (La Crosse virus and Rift Valley fever virus) also cause increased biting rates in infected vectors. Concomitantly, these data support the hypothesis that capacity to modify vector feeding behavior is a conserved trait among plant- and animal-infecting members of the Bunyaviridae that evolved as a mechanism to enhance virus transmission. Our results underscore the evolutionary importance of vector behavioral modification to diverse parasites with host ranges spanning both plant and animal kingdoms.

Tospovirus replication in insect vector cells: immunocytochemical evidence that the nonstructural protein encoded by the S RNA of tomato spotted wilt tospovirus is present in thrips vector cells.

Abstract: Tomato spotted wilt tospovirus (TSWV) is an insect-transmitted virus that is the type member of the Tospovirus genus, which is the only genus in the family Bunyaviridae containing viruses that infect plants. Direct evidence that Tospoviruses replicate in their thrips vectors has been difficult to obtain because of limitations to definitively detect replicative intermediates of TSWV or to immunolabel vector tissues. A nonstructural protein is encoded by the small RNA of TSWV, and translation of the NSs protein occurs from a subgenomic RNA formed after transcription of viral sense RNA. This protein is designated as nonstructural because it is found only in TSWV-infected cells and has not been found in assembled virions []

Cross-talk between jasmonate and salicylate plant defense pathways: effects on several plant parasites

Abstract: Plants are often attacked by many herbivorous insects and pathogens at the same time. Two important suites of responses to attack are mediated by plant hormones, jasmonate and salicylate, which independently provide resistance to herbivorous insects and pathogens, respectively. Several lines of evidence suggest that there is negative cross-talk between the jasmonate and salicylate response pathways. This biochemical link between general plant defense strategies means that deploying defenses against one attacker can positively or negatively affect other attackers. In this study, we tested for cross-talk in the jasmonate and salicylate signaling pathways in a wild tomato and examined the effects of cross-talk on an array of herbivores of cultivated tomato plants. In the wild cultivar, induction of defenses signaled by salicylate reduced biochemical expression of the jasmonate pathway but did not influence performance of S. exigua caterpillars. This indicates that the signal interaction is not a result of agricultural selection. In cultivated tomato, biochemical attenuation of the activity of a defense protein (polyphenol oxidase) in dual-elicited plants resulted in increased of performance of cabbage looper caterpillars, but not thrips, spider mites, hornworm caterpillars or the bacteria Pseudomonas syringae pv. tomato. In addition, we tested the effects of jasmonate-induced resistance on the ability of thrips to vector tomato spotted wilt virus. Although thrips fed less on induced plants, this did not affect the level of disease. Thus, the negative interaction between jasmonate and salicylate signaling had biological consequences for two lepidopteran larvae but not for several other herbivores tested or on the spread of a disease.

Plant pathogens and integrated defence responses to infection.

Abstract: Plants cannot move to escape environmental challenges. Biotic stresses result from a battery of potential pathogens: fungi, bacteria, nematodes and insects intercept the photosynthate produced by plants, and viruses use replication machinery at the host's expense. Plants, in turn, have evolved sophisticated mechanisms to perceive such attacks, and to translate that perception into an adaptive response. Here, we review the current knowledge of recognition-dependent disease resistance in plants. We include a few crucial concepts to compare and contrast plant innate immunity with that more commonly associated with animals. There are appreciable differences, but also surprising parallels.

Systemic acquired resistance

Abstract: Systemic acquired resistance (SAR) is a mechanism of induced defense that confers long-lasting protection against a broad spectrum of microorganisms. SAR requires the signal molecule salicylic acid (SA) and is associated with accumulation of pathogenesis-related proteins, which are thought to contribute to resistance. Much progress has been made recently in elucidating the mechanism of SAR. Using the model plant Arabidopsis, it was discovered that the isochorismate pathway is the major source of SA during SAR. In response to SA, the positive regulator protein NPR1 moves to the nucleus where it interacts with TGA transcription factors to induce defense gene expression, thus activating SAR. Exciting new data suggest that the mobile signal for SAR might be a lipid molecule. We discuss the molecular and genetic data that have contributed to our understanding of SAR and present a model describing the sequence of events leading from initial infection to the induction of defense genes.

Plant Immunity to Insect Herbivores

Abstract: Herbivorous insects use diverse feeding strategies to obtain nutrients from their host plants. Rather than acting as passive victims in these interactions, plants respond to herbivory with the production of toxins and defensive proteins that target physiological processes in the insect. Herbivore-challenged plants also emit volatiles that attract insect predators and bolster resistance to future threats. This highly dynamic form of immunity is initiated by the recognition of insect oral secretions and signals from injured plant cells. These initial cues are transmitted within the plant by signal transduction pathways that include calcium ion fluxes, phosphorylation cascades, and, in particular, the jasmonate pathway, which plays a central and conserved role in promoting resistance to a broad spectrum of insects. A detailed understanding of plant immunity to arthropod herbivores will provide new insights into basic mechanisms of chemical communication and plant-animal coevolution and may also facilitate new approaches to crop protection and improvement.

Induced systemic resistance by beneficial microbes

Abstract: Beneficial microbes in the microbiome of plant roots improve plant health. Induced systemic resistance (ISR) emerged as an important mechanism by which selected plant growth–promoting bacteria and fungi in the rhizosphere prime the whole plant body for enhanced defense against a broad range of pathogens and insect herbivores. A wide variety of root-associated mutualists, including Pseudomonas, Bacillus, Trichoderma, and mycorrhiza species sensitize the plant immune system for enhanced defense without directly activating costly defenses. This review focuses on molecular processes at the interface between plant roots and ISR-eliciting mutualists, and on the progress in our understanding of ISR signaling and systemic defense priming. The central role of the root-specific transcription factor MYB72 in the onset of ISR and the role of phytohormones and defense regulatory proteins in the expression of ISR in aboveground plant parts are highlighted. Finally, the ecological function of ISR-inducing microbes in the root microbiome is discussed.

The Myriad Plant Responses to Herbivores.

Abstract: Plant responses to herbivores are complex. Genes activated on herbivore attack are strongly correlated with the mode of herbivore feeding and the degree of tissue damage at the feeding site. Phloem-feeding whiteflies and aphids that produce little injury to plant foliage are perceived as pathogens and activate the salicylic acid (SA)-dependent and jasmonic acid (JA)/ethylene-dependent signaling pathways. Differential expression of plant genes in response to closely related insect species suggest that some elicitors generated by phloem-feeding insects are species-specific and are dependent on the herbivore's developmental stage. Other elicitors for defense-gene activation are likely to be more ubiquitous. Analogies to the pathogen-incompatible reactions are found. Chewing insects such as caterpillars and beetles and cell-content feeders such as mites and thrips cause more extensive tissue damage and activate wound-signaling pathways. Herbivore feeding is not equivalent to mechanical wounding. Wound responses are a part of the induced responses that accompany herbivore feeding. Herbivores induce direct defenses that interfere with herbivore feeding, growth and development, fecundity, and fertility. In addition, herbivores induce an array of volatiles that creates an indirect mechanism of defense. Volatile blends provide specific cues to attract herbivore parasites and predators to infested plants. The nature of the elicitors for volatile production is discussed.