Background: Translational and post-translational protein modifications play a key role in the response of plants to pathogen infection. Among the latter, phosphorylation is critical in modulating protein structure, localization and interaction with other partners. In this work, we used a multiplex staining approach with 2D gels to study quantitative changes in the proteome and phosphoproteome of Flavescence dorée-affected and recovered ‘Barbera’ grapevines, compared to healthy plants. Results: We identified 48 proteins that differentially changed in abundance, phosphorylation, or both in response to Flavescence dorée phytoplasma infection. Most of them did not show any significant difference in recovered plants, which, by contrast, were characterized by changes in abundance, phosphorylation, or both for 17 proteins not detected in infected plants. Some enzymes involved in the antioxidant response that were up-regulated in infected plants, such as isocitrate dehydrogenase and glutathione S-transferase, returned to healthy-state levels in recovered plants. Others belonging to the same functional category were even down-regulated in recovered plants (oxidoreductase GLYR1 and ascorbate peroxidase). Our proteomic approach thus agreed with previously published biochemical and RT-qPCR data which reported down-regulation of scavenging enzymes and accumulation of H₂O₂ in recovered plants, possibly suggesting a role for this molecule in remission from infection. Fifteen differentially phosphorylated proteins (| ratio | > 2, p < 0.05) were identified in infected compared to healthy plants, including proteins involved in photosynthesis, response to stress and the antioxidant system. Many were not differentially phosphorylated in recovered compared to healthy plants, pointing to their specific role in responding to infection, followed by a return to a steady-state phosphorylation level after remission of symptoms. Gene ontology (GO) enrichment and statistical analysis showed that the general main category “response to stimulus” was over-represented in both infected and recovered plants but, in the latter, the specific child category “response to biotic stimulus” was no longer found, suggesting a return to steady-state levels for those proteins specifically required for defence against pathogens. Conclusions: Proteomic data were integrated into biological networks and their interactions were represented through a hypothetical model, showing the effects of protein modulation on primary metabolic ways and related secondary pathways. By following a multiplex-staining approach, we obtained new data on grapevine proteome pathways that specifically change at the phosphorylation level during phytoplasma infection and following recovery, focusing for the first time on phosphoproteome changes during pathogen infection in this host.

The transition from vegetative mycelium to fruit body in truffles requires differentiation processes which lead to edible fruit bodies (ascomata) consisting of different cell and tissue types. The identification of genes differentially expressed during these developmental processes can contribute greatly to a better understanding of truffle morphogenesis. A cDNA library was constructed from vegetative mycelium RNAs of the white truffle Tuber borchii , and 214 cDNAs were sequenced. Up to 58% of the expressed sequence tags corresponded to known genes. The majority of the identified sequences represented housekeeping proteins, i.e., proteins involved in gene or protein expression, cell wall formation, primary and secondary metabolism, and signaling pathways. We screened 171 arrayed cDNAs by using cDNA probes constructed from mRNAs of vegetative mycelium and ascomata to identify fruit body-regulated genes. Comparisons of signals from vegetative mycelium and fruit bodies bearing 15 or 70% mature spores revealed significant differences in the expression levels for up to 33% of the investigated genes. The expression levels for six highly regulated genes were confirmed by RNA blot analyses. The expression of glutamine synthetase, 5-aminolevulinic acid synthetase, isocitrate lyase, thioredoxin, glucan 1,3-β-glucosidase, and UDP-glucose:sterol glucosyl transferase was highly up-regulated, suggesting that amino acid biosynthesis, the glyoxylate cycle pathway, and cell wall synthesis are strikingly altered during morphogenesis.

The genome sequences of mycorrhizal fungi will provide new opportunities for studying the biology and the evolution underlying this symbiotic lifestyle. The generation of null mutants at the wild-type loci is one of the best methods for gene-function assignment in the post-genomic era. To our knowledge, the generation of superoxide dismutase 1 (SOD1)-null mutants in the ericoid mycorrhizal fungus Oidiodendron maius is the first example of a gene-targeted disruption via homologous recombination in a mycorrhizal fungus. The disruption of OmSOD1 by Agrobacterium-mediated transformation resulted in the presence of oxidative stress markers, even in the absence of external superimposed stresses, and an increased sensitivity to reactive oxygen species (ROS)-generating substances, especially to menadione. A reduction in conidiation and in the percentage of mycorrhization of Vaccinium myrtillus roots was also observed. The latter findings establish the pivotal role of SOD1 as an important factor in the relationship between O. maius and its symbiotic partner. The lack of this ROS-scavenger may cause an imbalance in the redox homeostasis during host colonization and an alteration in the delicate dialogue between the fungus and its host plant.

Molecular changes associated with response to powdery mildew (PM) caused by Erysiphe necator have been largely explored in Vitis vinifera cultivars, but little is known on transcriptional and metabolic modifications following application of resistance elicitors against this disease. In this study, the whole transcriptome sequencing, and hormone and metabolite analyses were combined to dissect long-term defense mechanisms induced by molecular reprogramming events in PM-infected ‘Moscato’ and ‘Nebbiolo’ leaves treated with three resistance inducers: acibenzolar-S-methyl, potassium phosphonate, and laminarin. Although all compounds were effective in counteracting the disease, acibenzolar-S-methyl caused the most intense transcriptional modifications in both cultivars. These involved a strong down-regulation of photosynthesis and energy metabolism and changes in carbohydrate accumulation and partitioning that most likely shifted the plant growth-defense trade-off towards the establishment of disease resistance processes. It was also shown that genotype-associated metabolic signals significantly affected the cultivar defense machinery. Indeed, ‘Nebbiolo’ and ‘Moscato’ built up different defense strategies, often enhanced by the application of a specific elicitor, which resulted in either reinforcement of early defense mechanisms (e.g., epicuticular wax deposition and overexpression of pathogenesis-related genes in ‘Nebbiolo’), or accumulation of endogenous hormones and antimicrobial compounds (e.g., high content of abscisic acid, jasmonic acid, and viniferin in ‘Moscato’).

Two bacterial symbionts of the European pest leafhopper, Macrosteles quadripunctulatus (Hemiptera: Cicadellidae), were fully sequenced. “ Candidatus Sulcia muelleri” and “ Ca . Nasuia deltocephalinicola” represent two of the smallest known bacterial genomes at 190 kb and 112 kb, respectively. Genome sequences are nearly identical to strains reported from the closely related host species, M. quadrilineatus .

Two full-length cDNAs (OmZnT1 and OmFET) encoding membrane transporters were identified by yeast functional screening in the heavy metal tolerant ericoid mycorrhizal isolate Oidiodendron maius Zn. OmZnT1 belongs to the Zn-Type subfamily of the cation diffusion facilitators, whereas OmFET belongs to the family of iron permeases. Their properties were investigated in yeast by functional complementation of mutants affected in metal uptake and metal tolerance. Heterologous expression of OmZnT1 and OmFET in a Zn-sensitive yeast mutant restored the wild-type phenotype. Additionally, OmZnT1 expression also restored cobalt tolerance in a Co-sensitive mutant. A GFP fusion protein revealed that OmZnT1 was targeted to the endoplasmic reticulum membrane, a result consistent with a function for OmZnT1 in metal sequestration. Similarly to other iron permeases, OmFET-GFP was localized on the plasma membrane. OmFET restored the growth of uptake-defective strains for iron and zinc. Zinc-sensitive yeast mutants expressing OmFET specifically accumulated magnesium, as compared to cells transformed with the empty vector. We suggest that OmFET may counteract zinc toxicity by increasing entry of magnesium into the cell.