Giuseppe Patrignani

The Origin of Clonal Diversity and Structure of Populus alba in Sardinia: Evidence from Nuclear and Plastid Microsatellite Markers

BACKGROUND AND AIMS Populus alba is a thermophilic forest tree present in the Mediterranean basin. Its habitat is highly fragmented and its distribution range has been subject to long-term human interference, resulting in debate surrounding whether certain populations are native or exotic in origin. In particular, populations from the islands of Corsica and Sardinia are of uncertain origin. While populations of P. alba mainly reproduce sexually, clonal reproduction is also common. The aims of this study were to locate and molecularly characterize the poorly studied island populations of P. alba and compare these with samples from various spatial scales, in order to provide information on the genetic structure and phylogeography of this species. This information will provide evidence on whether the species is native to Sardinia, which is important for the development of conservation strategies. METHODS DNA extracts were obtained from the following P. alba trees: 159 from Sardinia, 47 from Ticino regional park (northern Italy), 15 acquired from an Italian Germoplasm Bank (IRC; Italian Reference Collection) and 28 from the Mediterranean basin (MB). Genetic polymorphisms were revealed at nuclear and chloroplast DNA (cpDNA) microsatellite loci, both at the island scale (Sardinia) and at broader scales, for comparative assessment of the genetic and genotypic diversity and phylogeography. KEY RESULTS Based on nuclear microsatellite loci, Sardinian white poplar consists of a small number of genets (26), each of which is represented by several ramets. Despite the uniqueness of the Sardinian haplotypes and the very low value of genetic diversity at the cpDNA level (vK = 0.15), the HT (0.60) and the AR (3.61) values, estimated at the nuclear level for Sardinia, were comparable with those of the other populations and collections. CONCLUSIONS The uniqueness of the cpDNA haplotypes, the prevalence of clonality and the restricted number of genets recorded suggest that Sardinian white poplar could be a floristic relict of the native flora of the island, which has spread through available habitats on the island mainly by means of vegetative propagation and human activities.

Ultrastructural studies on the developing secretory nodules of Hypericum perforatum

Summary The secretory nodule of Hypericum perforatum represents a very interesting gland. In fact, many of its active compounds, such as hypericin and hyperforin, are therapeutic agents. We observed, by transmission electron microscopy, the development of the structures, which appeared different from most plant glands, in leaves of H. perforatum . As observed by several authors, they appeared as a solid black cluster of cells without cavities and with some particular cell structures. Generally, young nodules show meristematic features. During development, cellular components degenerate and secrete materials accumulated first in vacuoles and then in a periplasmic space and cell walls. Finally, the cells were filled with black material. The outer flat cells surrounding the nodules appeared morphologically different from the inner cells and showed unusual vesicles in the periplasmic spaces. Ultrastructural observations suggest the secretion of materials could be eccrine.

Genetic structure and introgression in riparian populations of Populus alba L.

Abstract White poplar (Populus alba) is a widespread species of the northern hemisphere. Introgressed populations or hybrid zones with the related species of the European aspen (Populus tremula) have been suggested as potential venues for the identification of functionally important variation for germplasm conservation, restoration efforts and tree breeding. Data on the genetic diversity and structure of introgressed P. alba are available only for sympatric populations from central Europe. Here, clonality, introgression and spatial genetic patterns were evaluated in three riparian populations of P. alba along the Ticino, Paglia‐Tevere and Cesano river drainages in Italy. Samples of all three populations were typed for five nuclear microsatellite markers and 137 polymorphic amplified fragment length polymorphisms. Microsatellite‐based inbreeding co‐efficients (F IS) were significantly positive in all three populations. Genetic diversity was consistently highest in Ticino, the population with the highest level of introgression from P. tremula. Population differentiation (F ST) was low between the Ticino valley in northern Italy and the Cesano valley in central Italy and between the central Italian populations of Cesano and Paglia‐Tevere, consistent with a role of the Appenine mountain range as a barrier to gene flow between adjacent drainage areas. Introgression was not the primary determinant of within‐population spatial genetic structure (SGS) in the studied populations.

Nucleus and nucleolus in pea root meristems are affected by variations in moisture content

ABSTRACT This paper examines the morphological and biochemical variations occurring in the nucleus when considerable changes in moisture content take place in the tissue. The tissue used for this investigation was the root meristem of Pisum sativum L. at three different developmental stages: during seed maturation, during seed germination and during a vegetative stage. These different developmental stages were representative of three different degrees of moisture content. Seed maturation represented the case of tissue undergoing desiccation whereas seed germination represented the case of tissue undergoing hydration. PEG-treated seedlings represented the case of a vegetative tissue subjected to water stress. The data demonstrated that when moisture content in root meristems was low, the nucleus underwent a reduction in diameter and a change in chromatin arrangement. The nucleolus shrank considerably in diameter and became less visible. These events were simultaneous to qualitative and quantitative variati...

Modification of chromatin organisation at low water potential in cultured cells of Solanum tuberosum: Possible involvement of dehydrins

ABSTRACT To understand the mechanisms which enable the nucleus to function under low water potential, the morphology and biochemistry of potato cell nuclei were studied. Conformational modifications were observed in the chromatin of nuclei of cells growing under low water potential. These modifications include a higher number of heterochromatic centres, enlargement of the nuclear diameter, and a different accessibility of DNA to the action of restriction enzymes. Biochemical analyses showed that these chromatin modifications may coincide with quantitative and qualitative variations of several nuclear proteins, some of which may belong to the dehydrin family. We especially focussed our attention on a 45-kDa protein that is heat-stable and is recognised by an antibody raised against the conserved domain of dehydrins. The survival of potato cells in an environment where water availability is low may depend on several simultaneous events regarding the nucleus. The accumulation in the nucleus of specific proteins such as dehydrins could be required to stabilise the chromatin by means of their molecule-salvation action. Further studies are in progress to check whether or not variations in chromatin organisation may be one of the numerous traits that a cell must acquire to become water-stress resistant.

Spatial arrangement of the fibres in developing and mature endocarp of Luffa cylindrica Roem

ABSTRACT Luffa cylindrica bears peculiar pepo-like fruits, which are characterised by a fibrous endocarp. Mature endocarps, so far utilised as a “vegetable sponge“, are the object of studies for packing devices. By means of scanning, fluorescence and confocal microscopes, we investigated the arrangement and composition of the fibres in Luffa endocarps at different developmental stages in order to explain their functional properties.

Leaf morphology and carbon isotope discrimination values in eyebane (Euphorbia maculata L.)

Abstract Within the Euphorbiaceae, there are species belonging to the C3, C4 and CAM photosynthetic groups. Leaf anatomy and ultrastructure together with carbon isotope discrimination measurements indicated that Euphorbia maculata L., grown and collected in an urban area, is a C4 species ascribable to the NADP‐ME photosynthetic type.

Ultrastructure of the stem of the aquatic plantCallitriche stagnalis L.

The submerged stem ofCallitriche stagnalis L. has been studied by light and electron microscopy. The presence of plastids with an “opaque body” are noted in the parenchymatic cells near the conducting elements as well as many microtubules associated with polyribosomes and vesicles near the cell wall. It is of particular interest to note that the tracheids are connected to the pith lacuna and each other to form only one conducting cylinder, so that functionally theCallitriche stele seems to be a protostele. This reduction of the stele is probably due to the environment conditions, since by floral morphology this aquatic plant is considered an evolved species.

Proteins and chlorophyllase activity in Hedera helix L. with green or variegated leaves

Abstract Chlorophyllase activity and photosynthetic membrane proteins of two lots of Hedera helix were studied. Both the HV variety with variegated leaves and HC variety with green leaves were observed. Proteins from green, white and white-green portions of leaves differing in age were compared using dodecyl-sulfate-polyacrylamide gel electrophoresis. The white or white-green regions of Hedera helix var. aureomarginata (HV) did not differ significantly in chlorophyllase activity.