Integrated approach to investigate molecular mechanisms in woody root response to bending

The studies presented in this PhD thesis have the general aim to contribute in the understanding the complex and almost unknown “world” of woody root biology. In particular the work has been focused on two major issues: 1) root response to mechanical stress and 2) mechanisms involved in lateral root emission from a secondary structure. Results of these studies are described in the chapter I and chapter II. Chapter I. The response of Populus nigra woody root to mechanical stress imposed by bending. To investigate the root response to mechanical stress, during the first period of the PhD project an experimental system represented by bent poplar taproots has been set up. The first results obtained by the analysis of this experimental system are reported in the paper published by Scippa et al., (2008). The data obtained showed that poplar taproot responds to mechanical stress increasing the lateral root emissions, biomass and lignin content, activating stress-responsive genes and altering the metabolic pathways. Starting from these results, in the second phase, to dissect the mechanisms involved in the woody root response to bending a temporal and spatial analysis have been carried out. In particular after modeling the forces distribution along the bent taproot, the morphological and lignin changes were analyzed together with the alteration of proteins profiles. The use of 2DE coupled to the MS/MS allowed the identification of 211 well resolved proteins which represent the first woody root proteome map. In addition all the data obtained at the different level of investigation were further verified and elaborated by multivariate statistical analysis identifying important temporal and spatial protein markers. Chapter II. Identification and characterization of an activation-tagged gene encoding an AP2/ERF protein that regulates lateral root emission. To investigate mechanisms involved in lateral root emission from a secondary structure, a suitable experimental system is required. In details, after screening of 627 independent activation-tagged transgenic lines in tissue culture, a transgenic hybrid poplar (Populus tremula X Populus alba), with dominant root phenotype, was identified. The cause of the observed phenotype was the hyperactivation (insertion of a strong 35S transcriptional enhancer) of the gene encoding for a protein of AP2/ERF family (PtaERF003). The root phenotype was increased through IAA application to the growth medium and metabolic profiling was characterized. The data obtained address the use of the transgene as model to further identify the molecular factors controlling lateral root emission from the secondary growth. In addition the possibility of producing trees with strongly lateral root phenotype could have significant economic and environmental benefits, including ensure of a good anchorage, slopes stabilization and reduced risk of landslides.Dottorato di ricerca in Ambiente e Territorio (XXII ciclo

Lentils biodiversity: the characterization of two local landraces

A multi-disciplinary approach was used to characterize two autochthonous lentil landraces from Molise region (Central Italy). Different mature seed populations for each landrace were provided by the Molise Germoplasm Bank at the University of Molise (Pesche, Italy), and analyzed at the morphological and molecular (DNA and protein) levels. Nuclear ISSR markers were used to assess genetic differences, whereas phenotypic variability was detected by biochemical (proteomics) and morphological analyses. The genetic and phenotypic diversity of the two lentil landraces were well assessed in relation to their geographical provenance, supporting further studies to identify landrace markers

Reaction Wood Anatomical Traits and Hormonal Profiles in Poplar Bent Stem and Root

Reaction wood (RW) formation is an innate physiological response of woody plants to counteract mechanical constraints in nature, reinforce structure and redirect growth toward the vertical direction. Differences and/or similarities between stem and root response to mechanical constraints remain almost unknown especially in relation to phytohormones distribution and RW characteristics. Thus, Populus nigra stem and root subjected to static non-destructive mid-term bending treatment were analyzed. The distribution of tension and compression forces was firstly modeled along the main bent stem and root axis; then, anatomical features, chemical composition, and a complete auxin and cytokinin metabolite profiles of the stretched convex and compressed concave side of three different bent stem and root sectors were analyzed. The results showed that in bent stems RW was produced on the upper stretched convex side whereas in bent roots it was produced on the lower compressed concave side. Anatomical features and chemical analysis showed that bent stem RW was characterized by a low number of vessel, poor lignification, and high carbohydrate, and thus gelatinous layer in fiber cell wall. Conversely, in bent root, RW was characterized by high vessel number and area, without any significant variation in carbohydrate and lignin content. An antagonistic interaction of auxins and different cytokinin forms/conjugates seems to regulate critical aspects of RW formation/development in stem and root to facilitate upward/downward organ bending. The observed differences between the response stem and root to bending highlight how hormonal signaling is highly organ-dependent

The effects of biochar and its combination with compost on lettuce (Lactuca sativa L.) growth, soil properties, and soil microbial activity and abundance

Impacts of biochar application in combination with organic fertilizer, such as compost, are not fully understood. In this study, we tested the effects of biochar amendment, compost addition, and their combination on lettuce plants grown in a soil poor in nutrients; soil microbiological, chemical, and physical characteristics were analyzed, together with plant growth and physiology. An initial screening was also done to evaluate the effect of biochar and compost toxicity, using cress plants and earthworms. Results showed that compost amendment had clear and positive effects on plant growth and yield and on soil chemical characteristics. However, we demonstrated that also the biochar alone stimulated lettuce leaves number and total biomass, improving soil total nitrogen and phosphorus contents, as well as total carbon, and enhancing related microbial communities. Nevertheless, combining biochar and compost, no positive synergic and summative effects were observed. Our results thus demonstrate that in a soil poor in nutrients the biochar alone could be effectively used to enhance soil fertility and plant growth and biomass yield. However, we can speculate that the combination of compost and biochar may enhance and sustain soil biophysical and chemical characteristics and improve crop productivity over time