Modulation of class III peroxidase pathways and phenylpropanoids in Arundo donax under salt and phosphorus stress.

Arundo donax L. is an invasive species that has been recently employed for biomass production due to its well-known ability to colonize harsh environment. Based on previous observations, the present study investigated the potential role of phenylpropanoids and class III peroxidases to confer adaptation through biochemical and transcriptomic analysis in A. donax after Na+ and P excess supply, both in single stress and in combination, and after growth at low P level. The levels of hydrogen peroxide, flavonoids (i.e., quercetin, apigenin and kaempferol derivatives) and the activity of class III peroxidases, as well as the expression of several genes encoding for their enzymes involved in their biosynthesis, increased when Na+ was supplied in combination with P. These results suggest that those biomolecules are involved in the response of A. donax, to the presence of +Na and P in the soil. Moreover, even though at the sampling time no significant accumulation of lignin has been determined, the trend of accumulation of such metabolite and most of all the increase of several transcripts involved in its synthesis was found. This work for the first time indicates the need for further investigation devoted to elucidating whether the strengthening of cell walls via lignin synthesis is one of the mechanisms used by A. donax to adapt to harsh environments.

Transcription factors PRE3 and WOX11 are involved in the formation of new lateral roots from secondary growth taproot in A. thaliana.

The spatial deployment of lateral roots determines the ability of a plant to interact with the surrounding environment for nutrition and anchorage. This paper shows that besides the pericycle, the vascular cambium becomes active in Arabidopsis thaliana taproot at a later stage of development and is also able to form new lateral roots. To demonstrate the above, we implemented a two-step approach in which the first step leads to development of a secondary structure in A. thaliana taproot, and the second applies a mechanical stress on the vascular cambium to initiate formation of a new lateral root primordium. GUS staining showed PRE3, DR5 and WOX11 signals in the cambial zone of the root during new lateral root formation. An advanced level of wood formation, characterized by the presence of medullar rays, was achieved. Preliminary investigations suggest the involvement of auxin and two transcription factors (PRE3/ATBS1/bHLH135/TMO7 and WOX11) in the transition of some vascular cambium initials from a role as producers of xylem/phloem mother cells to founder cells of a new lateral root primordium.

The influence of slope on Spartium junceum root system: morphological, anatomical and biomechanical adaptation.

Root systems have a pivotal role in plant anchorage and their mechanical interactions with the soil may contribute to soil reinforcement and stabilization of slide-prone slopes. In order to understand the responses of root system to mechanical stress induced by slope, samples of Spartium junceum L., growing in slope and in plane natural conditions, were compared in their morphology, biomechanical properties and anatomical features. Soils sampled in slope and plane revealed similar characteristics, with the exception of organic matter content and penetrometer resistance, both higher in slope. Slope significantly influenced root morphology and in particular the distribution of lateral roots along the soil depth. Indeed, first-order lateral roots of plants growing on slope condition showed an asymmetric distribution between up- and down-slope. Contrarily, this asymmetric distribution was not observed in plants growing in plane. The tensile strength was higher in lateral roots growing up-slope and in plane conditions than in those growing down-slope. Anatomical investigations revealed that, while roots grown up-slope had higher area covered by xylem fibers, the ratio of xylem and phloem fibers to root diameter did not differ among the three conditions, as also, no differences were found for xylem fiber cell wall thickness. Roots growing up-slope were the main contributors to anchorage properties, which included higher strength and higher number of fibers in the xylematic tissues. Results suggested that a combination of root-specific morphological, anatomical and biomechanical traits, determines anchorage functions in slope conditions.

Interspecific variation in functional traits of oak seedlings (Quercus ilex, Quercus trojana, Quercus virgiliana) grown under artificial drought and fire conditions.

To face summer drought and wildfire in Mediterranean-type ecosystems, plants adopt different strategies that involve considerable rearrangements of biomass allocation and physiological activity. This paper analyses morphological and physiological traits in seedlings of three oak species (Quercus ilex, Quercus trojana and Quercus virgiliana) co-occurring under natural conditions. The aim of this study was to evaluate species-specific characteristics and the response of these oak seedlings to drought stress and fire treatment. Seedlings were kept in a growth chamber that mimicked natural environmental conditions. All three species showed a good degree of tolerance to drought and fire treatments. Differences in specific biomass allocation patterns and physiological traits resulted in phenotypic differences between species. In Q. ilex, drought tolerance depended upon adjustment of the allocation pattern. Q. trojana seedlings undergoing mild to severe drought presented a higher photosystem II (PSII) efficiency than control seedlings. Moreover, Q. trojana showed a very large root system, which corresponded to higher soil area exploitation, and bigger leaf midrib vascular bundles than the other two species. Morphological and physiological performances indicated Q. trojana as the most tolerant to drought and fire. These characteristics contribute to a high recruitment potential of Q. trojana seedlings, which might be the reason for the dominance of this species under natural conditions. Drought increase as a result of climate change is expected to favour Q. trojana, leading to an increase in its spatial distribution.

An integrated approach to the characterization of two autochthonous lentil (Lens culinaris) landraces of Molise (south-central Italy).

Plant biodiversity must be safeguarded because it constitutes a resource of genes that may be used, for instance, in breeding programs. Lentil (Lens culinaris Medik.) is one of the most ancient crops of the Mediterranean region. Extensive differentiation of L. culinaris over millennia has resulted in a myriad of different landraces. However, in more recent times many landraces have disappeared consequent to environmental and socioeconomic changes. To promote the survival of endangered lentil landraces, we have investigated the genetic relationship between two ancient landrace cultivated in Capracotta and Conca Casale (Molise, south-central Italy) and widely spread commercial varieties using an integrated approach consisting of studies at morphological, DNA and protein level. Seeds of these two landraces were collected from local farmers and conserved in the Molise germoplasm bank. The two local landraces were well differentiated from each other, and the Conca Casale landrace was separated from the commercial varieties at morphological, protein and DNA level. The Capracotta landrace, was well separated from the commercial varieties, except Castelluccio di Norcia, at DNA level showing a more complex and heterogeneous segregation at morphological and biochemical level. The correlation between morphological, DNA and protein data, illustrates that proteomics is a powerful tool with which to complement the analysis of biodiversity in ecotypes of a single plant species and to identify physiological and/or environmental markers.

The H1 histone variant of tomato, H1-S, is targeted to the nucleus and accumulates in chromatin in response to water-deficit stress.

Water deficit has a significant impact on patterns of gene expression. Based on the deduced amino acid sequence, it has been proposed that the drought and abscisic acid-induced gene (his1-s) of tomato (Lycopersicon esculentum Mill.) encodes an H1 histone variant. To study the role of H1-S it is important to understand the expression characteristics of the protein. To identify the his1-s product in vivo the his1-s cDNA was fused to a (His)6 tag and overexpressed in Escherichia coli. The H1-S fusion protein was used to generate an antibody that recognized a protein with an apparent molecular weight of 31 kDa that accumulates in response to water deficit in the whole plant and detached leaves. A time course of his1-s expression showed that protein accumulation is delayed compared to the mRNA accumulation in both the whole plant and detached leaves. Cellular fractionation, immunofluorescence and H1-S::beta-glucuronidase fusion analyses in transgenic tissues were used to determine the cellular localization of H1-S. The results showed that H1-S accumulates in nuclei and is associated with chromatin of wilted tomato leaves. The drought- and abscisic acid-induced gene his1-s encodes a linker-histone subtype specifically accumulated in the nuclei and chromatin of tomato leaves subjected to water-deficit conditions. Although the molecular mechanism of H1-S function is still unclear, the expression characteristics of H1-S are consistent with a potential role of this protein in the regulation of gene expression in response to water deficit.