Microbial Symbionts in Insects Influence Down-Regulation of Defense Genes in Maize

Diabrotica virgifera virgifera larvae are root-feeding insects and significant pests to maize in North America and Europe. Little is known regarding how plants respond to insect attack of roots, thus complicating the selection for plant defense targets. Diabrotica virgifera virgifera is the most successful species in its genus and is the only Diabrotica beetle harboring an almost species-wide Wolbachia infection. Diabrotica virgifera virgifera are infected with Wolbachia and the typical gut flora found in soil-living, phytophagous insects. Diabrotica virgifera virgifera larvae cannot be reared aseptically and thus, it is not possible to observe the response of maize to effects of insect gut flora or other transient microbes. Because Wolbachia are heritable, it is possible to investigate whether Wolbachia infection affects the regulation of maize defenses. To answer if the success of Diabrotica virgifera virgifera is the result of microbial infection, Diabrotica virgifera virgifera were treated with antibiotics to eliminate Wolbachia and a microarray experiment was performed. Direct comparisons made between the response of maize root tissue to the feeding of antibiotic treated and untreated Diabrotica virgifera virgifera show down-regulation of plant defenses in the untreated insects compared to the antibiotic treated and control treatments. Results were confirmed via QRT-PCR. Biological and behavioral assays indicate that microbes have integrated into Diabrotica virgifera virgifera physiology without inducing negative effects and that antibiotic treatment did not affect the behavior or biology of the insect. The expression data and suggest that the pressure of microbes, which are most likely Wolbachia, mediate the down-regulation of many maize defenses via their insect hosts. This is the first report of a potential link between a microbial symbiont of an insect and a silencing effect in the insect host plant. This is also the first expression profile for a plant attacked by a root-feeding insect

Quorum sensing modulation of a putative glycosyltransferase gene cluster essential for Xanthomonas campestris biofilm formation

10.1111/j.1462-2920.2010.02288.xEnvironmental Microbiology12123159-3170ENMI

Response of mitochondrial alternative oxidase (AOX) to light signals

Mitochondrial alternative oxidase (AOX), the unique respiratory terminal oxidase in plants, catalyzes energy wasteful cyanide (CN)-resistant respiration and plays a role in optimizing photosynthesis. Recent studies from our group indicated that AOX plays a crucial role in chloroplast protection under extreme environments, such as high light (HL). Genetic data suggest that AOX is upregulated by light that was mediated by photoreceptors (phytochromes, phototropins and cryptochromes), and it also might have a particular role in relieving the overreduction of chloroplasts. Physiological analyses further suggest that AOX is essential for the dark-tolight transition, especially in the course of de-etiolation. In this mini-review, we highlight recent progress in understanding the beneficial interaction between photosynthesis and mitochondria metabolism and discuss the possible role and mechanism of AOX in dissipation of excess reduced equivalents for chloroplasts under high light condition