Phytoextraction efficiency of Pteris vittata grown on a naturally As-rich soil and characterization of As-resistant rhizosphere bacteria.

This study evaluated the phytoextraction capacity of the fern Pteris vittata grown on a natural arsenic-rich soil of volcanic-origin from the Viterbo area in central Italy. This calcareous soil is characterized by an average arsenic concentration of 750 mg kg-1, of which 28% is bioavailable. By means of micro-energy dispersive X-ray fluorescence spectrometry (µ-XRF) we detected As in P. vittata fronds after just 10 days of growth, while a high As concentrations in fronds (5,000 mg kg-1), determined by Inductively coupled plasma-optical emission spectrometry (ICP-OES), was reached after 5.5 months. Sixteen arsenate-tolerant bacterial strains were isolated from the P. vittata rhizosphere, a majority of which belong to the Bacillus genus, and of this majority only two have been previously associated with As. Six bacterial isolates were highly As-resistant (> 100 mM) two of which, homologous to Paenarthrobacter ureafaciens and Beijerinckia fluminensis, produced a high amount of IAA and siderophores and have never been isolated from P. vittata roots. Furthermore, five isolates contained the arsenate reductase gene (arsC). We conclude that P. vittata can efficiently phytoextract As when grown on this natural As-rich soil and a consortium of bacteria, largely different from that usually found in As-polluted soils, has been found in P. vittata rhizosphere.

Gene-ecology of durum wheat HMW glutenin reflects their diffusion from the center of origin.

The production of many food items processed from wheat grain relies on the use of high gluten strength flours. As a result, about 80% of the allelic variability in the genes encoding the glutenin proteins has been lost in the shift from landraces to modern cultivars. Here, the allelic variability in the genes encoding the high molecular weight glutenin subunits (HMW-GSs) has been characterized in 152 durum wheat lines developed from a set of landraces. The allelic composition at the two Glu-1 loci (Glu-A1 and -B1) was obtained at both the protein and the DNA level. The former locus was represented by three alleles, of which the null allele Glu-A1c was the most common. The Glu-B1 locus was more variable, with fifteen alleles represented, of which Glu-B1b (HMW-GSs 7 + 8), -B1d (6 + 8) and -B1e (20 + 20) were the most frequently occurring. The composition of HMW-GSs has been used to make inferences regarding the diffusion and diversification of durum wheat. The relationships of these allelic frequencies with their geographical distribution within the Mediterranean basin is discussed in terms of gene-ecology.

Proteomic analysis in the lichen Physcia adscendens exposed to cadmium stress.

This work was undertaken to explore the potential of proteomics to dissect parallel and consecutive events of cadmium stress response in the lichen Physcia adscendens (Fr.) H. Olivier. Thalli were exposed to 0 (control) and 36 microM Cd for 6, 18, 24 and 48 h. Two-dimensional electrophoresis and mass spectrometry analyses showed an 80-85% spot identity between 6 and 18 h vs. 24 and 48 h of Cd exposure. Putative heat-shock proteins and glutathione S-transferase generally increased their expression all over the Cd treatments. By contrast, ABC transporters were underexpressed after 6-18 h, but in some cases induced after 24-48 h of Cd exposure. The cytochrome P450 appeared to have a variable expression pattern over time. Overall these data suggest that a considerable importance in the response of P. adscendens thalli to Cd stress can be assumed by differential expression of various protein families.

Analysis of protein profiles of genetically modified potato tubers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Traceability of genetically modified (GM) foods demands the development of appropriate reliable techniques in order to identify and quantify peptide or nucleic acid residues in GM plants and food products through the food chain. In this study the applicability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was demonstrated for the characterization of proteins of transformed and untransformed potato (Solanum Tuberosum L.) tubers. In GM tubers the expression level of the G1-1 gene, which regulates transition from dormancy to sprouting tubers, was inhibited by antisense technology. The analysis of antisense transformed lines showed that several of them exhibited a significant delay in sprouting relative to the control lines, in accordance with a decrease in the transcript level. Preliminary attempts to compare the protein patterns obtained from transformed and control lines using traditional electrophoresis were not able to reveal differences in the low-kDa range. Instead, MALDI-TOFMS applied to total peptide extract without any purification was able to distinguish spectral patterns of transformed and untransformed lines. In particular, several characteristic peaks from m/z 4373 to 4932 were detected only in the mass spectra of GM tuber samples.

Differential display-mediated isolation of a genomic sequence for a putative mitochondrial LMW HSP specifically expressed in condition of induced thermotolerance in Arabidopsis thaliana (L.) heynh.

Plants of Arabidopsis thaliana pre-treated at 37 degrees C for 2 h can survive an otherwise lethal heat shock at 45 degrees C. Differential display reverse transcriptase-PCR (DDRT-PCR) was utilized to clone DNA fragments corresponding to mRNAs specifically expressed in conditions of induced thermotolerance or of expression of thermotolerance. One of these DDRT-PCR fragments enabled the isolation of a genomic clone pAt1.3EX, containing the sequence Athsp23.5, the gene for a low-molecular-weight (LMW) heat shock protein (HSP), AtHSP23.5. Athsp23.5 is low- or single-copy in the Arabidopsis genome and its open reading frame is interrupted by a 137 bp intron. Analysis of the sequence suggests AtHSP23.5 is targeted to the mitochondrion. The steady-state level of the AtHSP23.5 mRNA varied significantly according to the heat treatment, increasing on heat shock (transfer from 22 degrees C to 37 degrees C), with a further increase during expression of thermotolerance (transfer from 22 degrees C to 37 degrees C and then to 45 degrees C). Expression was low after an abrupt stress (from 22 degrees C to 45 degrees C). This behaviour was different from that observed for other LMW HSP mRNAs that were present at high level at 37 degrees C, but did not increase significantly in condition of expression of thermotolerance, and reached a considerable steady-state level also during the abrupt stress at 45 degrees C. The retrotranscription of AtHSP23.5 mRNA followed by amplification with two primers encompassing the intron allowed for the isolation of an almost full-length cDNA sequence. The sequence analysis of the two cDNAs obtained from condition 22 degrees C-->37 degrees C and condition 22 degrees C-->45 degrees C suggested that in both cases the intron had been correctly spliced. The importance of correct intron splicing in survival at high temperatures and the role of mitochondrial HSP in induction and expression of thermotolerance are discussed.