Analysis of the Molecular Dialogue Between Gray Mold (Botrytis cinerea) and Grapevine (Vitis vinifera) Reveals a Clear Shift in Defense Mechanisms During Berry Ripening.

Mature grapevine berries at the harvesting stage (MB) are very susceptible to the gray mold fungus Botrytis cinerea, while veraison berries (VB) are not. We conducted simultaneous microscopic and transcriptomic analyses of the pathogen and the host to investigate the infection process developed by B. cinerea on MB versus VB, and the plant defense mechanisms deployed to stop the fungus spreading. On the pathogen side, our genome-wide transcriptomic data revealed that B. cinerea genes upregulated during infection of MB are enriched in functional categories related to necrotrophy, such as degradation of the plant cell wall, proteolysis, membrane transport, reactive oxygen species (ROS) generation, and detoxification. Quantitative-polymerase chain reaction on a set of representative genes related to virulence and microscopic observations further demonstrated that the infection is also initiated on VB but is stopped at the penetration stage. On the plant side, genome-wide transcriptomic analysis and metabolic data revealed a defense pathway switch during berry ripening. In response to B. cinerea inoculation, VB activated a burst of ROS, the salicylate-dependent defense pathway, the synthesis of the resveratrol phytoalexin, and cell-wall strengthening. On the contrary, in infected MB, the jasmonate-dependent pathway was activated, which did not stop the fungal necrotrophic process.

Combined transcript, proteome, and metabolite analysis of transgenic maize seeds engineered for enhanced carotenoid synthesis reveals pleotropic effects in core metabolism.

The aim of this study was to assess whether endosperm-specific carotenoid biosynthesis influenced core metabolic processes in maize embryo and endosperm and how global seed metabolism adapted to this expanded biosynthetic capacity. Although enhancement of carotenoid biosynthesis was targeted to the endosperm of maize kernels, a concurrent up-regulation of sterol and fatty acid biosynthesis in the embryo was measured. Targeted terpenoid analysis, and non-targeted metabolomic, proteomic, and transcriptomic profiling revealed changes especially in carbohydrate metabolism in the transgenic line. In-depth analysis of the data, including changes of metabolite pools and increased enzyme and transcript concentrations, gave a first insight into the metabolic variation precipitated by the higher up-stream metabolite demand by the extended biosynthesis capacities for terpenoids and fatty acids. An integrative model is put forward to explain the metabolic regulation for the increased provision of terpenoid and fatty acid precursors, particularly glyceraldehyde 3-phosphate and pyruvate or acetyl-CoA from imported fructose and glucose. The model was supported by higher activities of fructokinase, glucose 6-phosphate isomerase, and fructose 1,6-bisphosphate aldolase indicating a higher flux through the glycolytic pathway. Although pyruvate and acetyl-CoA utilization was higher in the engineered line, pyruvate kinase activity was lower. A sufficient provision of both metabolites may be supported by a by-pass in a reaction sequence involving phosphoenolpyruvate carboxylase, malate dehydrogenase, and malic enzyme.

Sulfiredoxin protects mice from lipopolysaccharide-induced endotoxic shock.

Peroxiredoxins constitute a major family of cysteine-based peroxide-scavenging enzymes. They carry an intriguing redox switch by undergoing substrate-mediated inactivation via overoxidation of their catalytic cysteine to the sulfinic acid form that is reverted by reduction catalyzed by the sulfinic acid reductase sulfiredoxin (Srx). The biological significance of such inactivation is not understood, nor is the function of Srx1. To address this question, we generated a mouse line with a null deletion of the Srx1-encoding Srxn1 gene. We show here that Srxn1(-/-) mice are perfectly viable and do not suffer from any apparent defects under laboratory conditions, but have an abnormal response to lipopolysaccharide that manifests by increased mortality during endotoxic shock. Microarray-based mRNA profiles show that although the response of Srxn1(-/-) mice to lipopolysaccharide is typical, spanning all spectrum and all pathways of innate immunity, it is delayed by several hours and remains intense when the response of Srxn1(+/+) mice has already dissipated. These data indicate that Srx1 activity protects mice from the lethality of endotoxic shock, adding this enzyme to other host factors, as NRF2 and peroxiredoxin 2, which by regulating cellular reactive oxygen species levels act as important modifiers in the pathogenesis of sepsis.