What is a plant gall and how do insects make them?

Abstract only availableGalls are novel plant organs, produced under the insect's direction. These ecotopic organs provide food and shelter for the developing larvae. The cell of many galls are richer in starch and sugars than normal tissues and the insect uses this rich food to grow in a protected place. In a previous study of galls on grape leaves, the lab found that plant genes specifying the vegetative-to-reproductive transition and fruit and seed identity were expressed in developing galls. To fully test the hypothesis that insects make plant galls by upregulating fruit genes, one needs to block expression of the genes and show that a gall can't be made. This is difficult to do in grape but can be done in poplar, so we are working with galls on poplar leaves. In poplar leaves with or without galls, sectioned and stained using Toluene Blue O dye and examined under polarized light at 20 magnification, we identified changes that galls make in leaf development. We detected a number of histological changes in galled leaves, including patterning of xylem & phloem, palisade and spongy parenchyma. We prepared RNA from fruit, ungalled leaf and galled leaf to study diffences in their expression of meristem identity and carpel genes. Although we didn't have time to do the gene expression work, we predict that the expression of fruit genes will be elevated in the gall tissue compared to surrounding normal leaf tissue.Gyeongsang National Universit

The SIB Swiss Institute of Bioinformatics' resources: focus on curated databases

The SIB Swiss Institute of Bioinformatics (www.isb-sib.ch) provides world-class bioinformatics databases, software tools, services and training to the international life science community in academia and industry. These solutions allow life scientists to turn the exponentially growing amount of data into knowledge. Here, we provide an overview of SIB's resources and competence areas, with a strong focus on curated databases and SIB's most popular and widely used resources. In particular, SIB's Bioinformatics resource portal ExPASy features over 150 resources, including UniProtKB/Swiss-Prot, ENZYME, PROSITE, neXtProt, STRING, UniCarbKB, SugarBindDB, SwissRegulon, EPD, arrayMap, Bgee, SWISS-MODEL Repository, OMA, OrthoDB and other databases, which are briefly described in this article

The ecology and endemism of Cirsium pitcheri in Michigan.

http://deepblue.lib.umich.edu/bitstream/2027.42/53274/1/1708.pdfDescription of 1708.pdf : Access restricted to on-site users at the U-M Biological Station

Flexible resource allocation during plant defense responses

Plants are organisms composed of modules connected by xylem and phloem transport streams. Attack by both insects and pathogens elicits sometimes rapid defense responses in the attacked module. We have also known for some time that proteins are often reallocated away from pathogen-infected tissues, while the same infection sites may draw carbohydrates to them. This has been interpreted as a tug of war in which the plant withdraws critical resources to block microbial growth while the microbes attempt to acquire more resources. Sink-source regulated transport among modules of critical resources, particularly carbon and nitrogen, is also altered in response to attack. Insects and jasmonate can increase local sink strength, drawing carbohydrates that support defense production. Shortly after attack, carbohydrates may also be drawn to the root. The rate and direction of movement of photosynthate or signals in phloem in response to attack is subject to constraints that include branching, degree of connection among tissues, distance between sources and sinks, proximity, strength, and number of competing sinks, and phloem loading/unloading regulators. Movement of materials (e.g., amino acids, signals) to or from attack sites in xylem is less well understood but is partly driven by transpiration. The root is an influential sink and may regulate sink-source interactions and transport above and below ground as well as between the plant and the rhizosphere and nearby, connected plants. Research on resource translocation in response to pathogens or herbivores has focused on biochemical mechanisms; whole-plant research is needed to determine which, if any, of these plant behaviors actually influence plant fitness

Roles for jasmonate- and ethylene- induced transcription factors in the ability of Arabidopsis to respond differentially to damage caused by two insect herbivores

Plant responses to insects and wounding involve substantial transcriptional reprogramming that integrates hormonal, metabolic, and physiological events. The ability to respond differentially to various stresses, including wounding, generally involves hormone signaling and trans-acting regulatory factors. Evidence of the importance of transcription factors (TFs) in responses to insects is also accumulating. However, the relationships among hormone signaling, TF activity, and ability to respond specifically to different insects are uncertain. We examined transcriptional and hormonal changes in Arabidopsis thaliana after herbivory by larvae of two lepidopteran species, Spodoptera exigua (Hübner) and Pieris rapae L. over a 24-hour time course. Transcriptional responses to the two insects differed and were frequently weaker or absent in response to the specialist P. rapae. Using microarray analysis and qRT-PCR, we found 141 transcription factors, including many AP2/ERFs (Ethylene Response Factors) and selected defense-related genes, to be differentially regulated in response to the two insect species or wounding. Jasmonic Acid (JA), JA-isoleucine, and ethylene production by Arabidopsis plants increased after attack by both insect species. However, the amounts and timing of ethylene production differed between the two herbivory treatments. Our results support the hypothesis that the different responses to these two insects involve modifications of JA-signaling events and activation of different subsets of ERF transcription factors, resulting in different degrees of divergence from responses to wounding alone

Major Signaling Pathways Modulate Arabidopsis Glucosinolate Accumulation and Response to Both Phloem-Feeding and Chewing Insects

Plant responses to enemies are coordinated by several interacting signaling systems. Molecular and genetic studies with mutants and exogenous signal application suggest that jasmonate (JA)-, salicylate (SA)-, and ethylene (ET)-mediated pathways modulate expression of portions of the defense phenotype in Arabidopsis (Arabidopsis thaliana), but have not yet linked these observations directly with plant responses to insect attack. We compared the glucosinolate (GS) profiles of rosette leaves of 4-week-old mutant and transgenic Arabidopsis (Columbia) plants compromised in these three major signaling pathways, and characterized responses by those plants to feeding by two phloem-feeding aphids (generalist Myzus persicae and specialist Brevicoryne brassicae) and one generalist caterpillar species (Spodoptera exigua Hubner). Blocked JA signaling in coronatine-insensitive (coi1) and enhanced expression of SA-signaled disease resistance in hypersensitive response-like (hrl1) mutants reduced constitutive GS concentrations, while blocking SA signaling at the mediator protein npr1 mutant (NPR) increased them. There was no significant impact on constitutive GS contents of blocking ET signaling (at ET resistant [etr1]) or reducing SA concentrations (nahG transgene). We found increased GS accumulation in response to insect feeding, which required functional NPR1 and ETR1 but not COI1 or SA. Insect feeding caused increases primarily in short-chain aliphatic methylsulfinyl GS. By contrast, responses to exogenous JA, a frequent experimental surrogate for insect attack, were characterized by an increase in indolyl GS. Insect performance, measured as population increase or weight increase, was negatively related to GS levels, but we found evidence that other, ET-regulated factors may also be influential. Plant resistance to (consumption by) S. exigua was not related to insect growth because some plant chemistries inhibited growth while others inhibited feeding. These major signaling pathways modulate Arabidopsis GS accumulation and response to both phloem-feeding and chewing insects, often antagonistically; NPR appears to be central to these interactions. Our results indicate that exogenous signal application and plant consumption measures may not provide useful measures of plant responses to actual insect feeding

Herbivore-induced phenolic accumulation is dependent on the presence of intact source leaves.

<p>The accumulation of total phenolics (A,B), anthocyanins (C,D) and flavonoids (E,F) were measured locally, within herbivore-damaged leaves (A,C,E), and in young, systemic leaves (B,D,F). Bars represent means ±SE. n = 16/treatment group. Results of analysis of variance are summarized in Tables A-C in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123899#pone.0123899.s001" target="_blank">S1 File</a>. Asterisks indicate significant differences between clip-caged control and herbivore-damaged plants for a given leaf type (<i>P</i> < 0.05 Tukey’s <i>post hoc</i> comparisons).</p