No abstract

The maize gene b-32, normally expressed in the maize (Zea mays) endosperm, encodes for a RIP (Ribosome Inactivating Protein) characterised by antifungal activity. Transgenic wheat plants were obtained via biolistic transformation, in which the b-32 gene is driven by the 35SCaMV promoter in association with the bar gene as a selectable marker. Plants were brought to homozygosity through genetic analysis of progeny and pathogenicity tests were performed on the fourth generation. Six homozygous b-32 wheat lines were characterised. All plants had a normal phenotype, not distinguishable from the control cv. Veery except for slightly smaller size, flowered and set seeds. Western blot analyses confirmed b-32 expression during the plant life cycle in the various tissues. Each line differed in the b-32 content in leaf protein extracts and the transgenic protein expression level was maintained at least up to 10 days after anthesis. Pathogenicity tests for Fusarium head blight (FHB) were performed on the b-32 transgenic wheat lines in comparison to the parental cv. Veery. Resistance to FHB was evaluated by the single floret injection inoculation method on immature spikes with spores of Fusarium culmorum. In all the transgenic lines, a similar reduction in FHB symptoms, not dependent on the level of b-32 protein, has been observed (20% and 30% relative to the control, respectively 7 and 14 days after inoculation). Percentage of tombstone kernels at maturity was also recorded; in all transgenic lines disease control for this parameter was around 25%. The data obtained indicate that maize b-32 was effective as in vivo antifungal protein reducing FHB symptoms in wheat lines expressing the maize RIP protein.

A maize histone deacetylase gene was identified as a homolog of yeast Hda1. The predicted protein corresponds to a previously purified maize deacetylase that is active as a protein monomer with a molecular weight of 48,000 and is expressed in all tissues of germinating embryos. Hda1 is synthesized as an enzymatically inactive protein with an apparent molecular weight of 84,000 that is processed to the active 48-kD form by proteolytic removal of the C-terminal part, presumably via a 65-kD intermediate. The enzymatically inactive 84-kD protein also is part of a 300-kD protein complex of unknown function. The proteolytic cleavage of ZmHda1 is regulated during maize embryo germination in vivo. Expression of the recombinant full-length protein and the 48-kD form confirmed that only the smaller enzyme form is active as a histone deacetylase. In line with this finding, we show that the 48-kD protein is able to repress transcription efficiently in a reporter gene assay, whereas the full-length protein, including the C-terminal part, lacks full repression activity. This report on the processing of Hda1-p84 to enzymatically active Hda1-p48 demonstrates that proteolytic cleavage is a mechanism to regulate the function of Rpd3/Hda1-type histone deacetylases.

The agronomic management of symbiotic (S) inoculations, by means of bio-fertilizers (BF), is aimed at inducing modifications of the plant rhizosphere and thereafter of the phenotype and yield of the crop. It is here shown that the yield response of maize to a symbiotic treatment may be correlated to six easy-to-calculate indicator variables on the basis of the raw foliar pH, NIR-Spectroscopy of leaves, and the NIRS of hay litter-bags from soils. It has been confirmed, in a set of thirteen pairwise comparisons of Symbiotic (S) soil inoculated by BF vs. Control (non-inoculated soil; C), that the inoculation on average acidified the leaves by-3.7% pH units (P<0.0001). The responses in yield ranged from +25.2% to-9.2% (av.ge +3.5%; P = 0.03), but with average null responses in two centers and a significant response (+11%) in a third center. NIR-Tomoscopy scans (No. 574) were also performed on the leaves, and in addition, hay-litter-bags that had previously been buried in fields were dug up after two months, and 431 NIR-scans were acquired. The effect-size on the yield was expressed as the logarithm of the response ratio, i.e. the mean of the inoculated Symbiotic treatment divided by the mean of the non-inoculated Control for each pairwise comparison. A multiple regression model was developed to predict the symbiotic response to the treatment using six independent variables, including the squared litter-bag fingerprints, and an R 2 adj. level of 0.78 (P=0.01) was reached, with a standard error of ±4%. Validation in one external maize field, with a positive response to bio-fertilizers, demonstrates the juxtaposition of the estimated and accomplished yield. In a second experiment, with 40 pairwise comparisons, the two tested maize varieties did not respond to five types of bio-fertilizer, and the negative results were predicted at 84% (P 0.0012). The soil biota is a key factor for the application of appropriate microbial inoculants in the field, but the genotype/ genotype interactions between the microbial strain (s) and the crop cultivar (s) require prior screening to obtain the desired results.

We analysed a total of 2258 grain samples over a 3-year period (2006-2008) from 93 storage centers in the principal maize cultivation area of Italy to establish the levels of fumonisin contamination. Fumonisin concentrations were measured using ELISA (RIDASCREEN) fumonisin test kits. Mean levels of contamination were remarkably high in each year, with the highest value in 2006 (10.9 mg/kg) and the lowest in 2008 (4.8 mg/kg). Similarly, for each year, variations were quite large: from