Rootstock-scion interaction affecting citrus response to CTV infection: a proteomic view.

Citrus tristeza virus (CTV) is the causal agent of various diseases with dramatic effects on citrus crops worldwide. Most Citrus species, grown on their own roots, are symptomless hosts for many CTV isolates. However, depending on different scion-rootstock combination, CTV infection should result in distinct syndromes, being 'tristeza' the more severe one, leading to a complete decline of the susceptible plants in a few weeks. Transcriptomic analyses revealed several genes involved either in defense response, or systemic acquired resistance, as well as transcription factors and components of the phosphorylation cascades, to be differentially regulated during CTV infection in Citrus aurantifolia species. To date little is known about the molecular mechanism of this host-pathogen interaction, and about the rootstock effect on citrus response to CTV infection. In this work, the response to CTV infection has been investigated in tolerant and susceptible scion-rootstock combinations by two-dimensional gel electrophoresis (2DE). A total of 125 protein spots have been found to be differently accumulated and/or phosphorylated between the two rootstock combinations. Downregulation in tolerant plants upon CTV infection was detected for proteins involved in reactive oxygen species (ROS) scavenging and defense response, suggesting a probable acclimation response able to minimize the systemic effects of virus infection. Some of these proteins resulted to be modulated also in absence of virus infection, revealing a rootstock effect on scion proteome modulation. Moreover, the phospho-modulation of proteins involved in ROS scavenging and defense response, further supports their involvement either in scion-rootstock crosstalk or in the establishment of tolerance/susceptibility to CTV infection.

Morpho-physiolological and qualitative traits of a bread wheat collection spanning a century of breeding in Italy.

Evaluation and characterization are crucial steps in the exploitation of germplasm collections. The Sant'Angelo Lodigiano unit of the Consiglio per la ricerca in agricoltura e l'analisi dell'economia agraria (CREA) maintains a broad collection of Triticum spp, including more than 4000 genotypes of T. aestivum. Such collection represents a wide source of genetic variability for many agronomic and qualitative traits, extremely useful in modern breeding programs. The collection size, however, makes very difficult its management as a whole. A reduced subset, representing the process of wheat breeding in Italy during the last hundred years, was hence identified for an in-depth characterization. The lines were cropped in two locations over two growing seasons, and analyzed using 16 morpho-agronomic and qualitative descriptors. Most of the analysed characters showed a broad variation throughout the collection, allowing to follow the plant ideotype changes across the breeding progress in Italy during the 20th century.

Analysis of Quality-Related Parameters in Mature Kernels of Polygalacturonase Inhibiting Protein (PGIP) Transgenic Bread Wheat Infected with Fusarium graminearum.

Fusarium head blight, caused by the fungus Fusarium graminearum, has a detrimental effect on both productivity and qualitative properties of wheat. To evaluate its impact on wheat flour, we compared its effect on quality-related parameters between a transgenic bread wheat line expressing a bean polygalacturonase inhibiting protein (PGIP) and its control line. We have compared metabolic proteins, the amounts of gluten proteins and their relative ratios, starch content, yield, extent of pathogen contamination, and deoxynivalenol (DON) accumulation. These comparisons showed that Fusarium significantly decreases the amount of starch in infected control plants, but not in infected PGIP plants. The flour of PGIP plants contained also a lower amount of pathogen biomass and DON accumulation. Conversely, both gluten and metabolic proteins were not significantly influenced either by the transgene or by fungal infection. These results indicate that the transgenic PGIP expression reduces the level of infection, without changing significantly the wheat seed proteome and other quality-related parameters.

Emerging knowledge from genome sequencing of crop species.

Extensive insights into the genome composition, organization, and evolution have been gained from the plant genome sequencing and annotation ongoing projects. The analysis of crop genomes provided surprising evidences with important implications in plant origin and evolution: genome duplication, ancestral re-arrangements and unexpected polyploidization events opened new doors to address fundamental questions related to species proliferation, adaptation, and functional modulations. Detailed paleogenomic analysis led to many speculation on how chromosomes have been shaped over time in terms of gene content and order. The completion of the genome sequences of several major crops, prompted to a detailed identification and annotation of transposable elements: new hypothesis related to their composition, chromosomal distribution, insertion models, amplification rate, and evolution patterns are coming up. Availability of full genome sequence of several crop species as well as from many accessions within species is providing new keys for biodiversity exploitation and interpretation. Re-sequencing is enabling high-throughput genotyping to identify a wealth of SNP and afterward to produce haplotype maps necessary to accurately associate molecular variation to phenotype. Conservation genomics is emerging as a powerful tool to explain adaptation, genetic drift, natural selection, hybridization and to estimate genetic variation, fitness and population's viability.

Comparative proteome analysis of metabolic proteins from seeds of durum wheat (cv. Svevo) subjected to heat stress.

In Central and Southern Italy, where durum wheat represents one of the most widely cultivated crops, grain filling occurs during Spring, a period characterized by sudden increases in temperature. Wheat grain proteins are classified into albumins, globulins, and prolamins. The nonprolamin fractions include proteins with metabolic activity or structural function. In order to investigate the consequences of heat stress on the accumulation of nonprolamin proteins in mature durum wheat kernels, the Italian cultivar Svevo was subjected to two thermal regimes (heat stress versus control). The 2-D patterns of nonprolamin proteins were monitored to identify polypeptides affected by heat stress during grain fill. This study shows that heat stress alters significantly the durum wheat seed proteome, although the changes range is only between 1.2- and 2.2-fold. This analysis revealed 132 differentially expressed polypeptides, 47 of which were identified by MALDI-TOF and MALDI-TOF-TOF MS and included HSPs, proteins involved in the glycolysis and carbohydrate metabolism, as well as stress-related proteins. Many of the heat-induced polypeptides are considered to be allergenic for sensitive individuals.