Stefania Romeo

Proteomic analysis of Populus × euramericana (clone I-214) roots to identify key factors involved in zinc stress response.

Contamination of soil and water by heavy metals has become a widespread problem; environmental pollution by high zinc (Zn) concentration occurs frequently. Although poplar (Populus spp.) has been identified as suitable for phytoremediation approaches, its response to high Zn concentrations are still not clearly understood. For this reason, we investigated the effects of Zn in Populus×euramericana clone I-214 roots by proteomic analysis. Comparative experiments were conducted on rooted woody cuttings grown in nutrient solutions containing 1mM (treatment) or 1μM (control) Zn concentrations. A gel-based proteomic approach coupled with morphological and chemical analysis was used to identify differentially represented proteins in treated roots and to investigate the effect of Zn treatment on the poplar root system. Data shows that Zn was accumulated preferentially in roots, that the antioxidant system, the carbohydrate/energy and amino acid metabolisms were the main pathways modulated by Zn excess, and that mitochondria and vacuoles were the cellular organelles predominately affected by Zn stress. A coordination between cell death and proliferation/growth seems to occur under this condition to counteract the Zn-induced damage.

Heavy Metals Stress on Poplar: Molecular and Anatomical Modifications

Heavy metal stress responses vary from plant to plant depending on the type of heavy metals and require a coordinated interplay of complex physiological and biochemical processes, gene expression, protein modification and changes in metabolites compositions leading to proper stress signal and tolerance.

RNA sequencing of Populus x canadensis roots identifies key molecular mechanisms underlying physiological adaption to excess zinc

Populus x canadensis clone I-214 exhibits a general indicator phenotype in response to excess Zn, and a higher metal uptake in roots than in shoots with a reduced translocation to aerial parts under hydroponic conditions. This physiological adaptation seems mainly regulated by roots, although the molecular mechanisms that underlie these processes are still poorly understood. Here, differential expression analysis using RNA-sequencing technology was used to identify the molecular mechanisms involved in the response to excess Zn in root. In order to maximize specificity of detection of differentially expressed (DE) genes, we consider the intersection of genes identified by three distinct statistical approaches (61 up- and 19 down-regulated) and validate them by RT-qPCR, yielding an agreement of 93% between the two experimental techniques. Gene Ontology (GO) terms related to oxidation-reduction processes, transport and cellular iron ion homeostasis were enriched among DE genes, highlighting the importance of metal homeostasis in adaptation to excess Zn by P. x canadensis clone I-214. We identified the up-regulation of two Populus metal transporters (ZIP2 and NRAMP1) probably involved in metal uptake, and the down-regulation of a NAS4 gene involved in metal translocation. We identified also four Fe-homeostasis transcription factors (two bHLH38 genes, FIT and BTS) that were differentially expressed, probably for reducing Zn-induced Fe-deficiency. In particular, we suggest that the down-regulation of FIT transcription factor could be a mechanism to cope with Zn-induced Fe-deficiency in Populus. These results provide insight into the molecular mechanisms involved in adaption to excess Zn in Populus spp., but could also constitute a starting point for the identification and characterization of molecular markers or biotechnological targets for possible improvement of phytoremediation performances of poplar trees.

1H NMR and PCA-based analysis revealed variety dependent changes in phenolic contents of apple fruit after drying

Dry and fresh apples have been studied monitoring their polyphenolic profiles through 1H NMR, antioxidant capacity and total polyphenol content. Six ancient and underutilized apple varieties (Mantovana, Mora, Nesta, Cipolla, Ruggina, Sassola) and a commercial one (Golden Delicious) were dried with an air-drying system at 45°C for 19h. Although some of their polyphenol constituents were lost during drying, the antioxidant capacity of some apple varieties remained higher compared to Golden Delicious. This result is very important for ancient and underutilized varieties that are not consumed on large scale as fresh product since they have low attractiveness, due to their ugly appearance. Combining quantitative NMR spectroscopy with principal component analysis we have identified and quantified several polyphenols (such as catechin, epicathechin, and chlorogenic acid) that are important to establish the nutraceutical value of the different investigated apple varieties.