Sergio Mapelli

Ancient Humans Influenced the Current Spatial Genetic Structure of Common Walnut Populations in Asia

Common walnut (Juglans regia L) is an economically important species cultivated worldwide for its wood and nuts. It is generally accepted that J. regia survived and grew spontaneously in almost completely isolated stands in its Asian native range after the Last Glacial Maximum. Despite its natural geographic isolation, J. regia evolved over many centuries under the influence of human management and exploitation. We evaluated the hypothesis that the current distribution of natural genetic resources of common walnut in Asia is, at least in part, the product of ancient anthropogenic dispersal, human cultural interactions, and afforestation. Genetic analysis combined with ethno-linguistic and historical data indicated that ancient trade routes such as the Persian Royal Road and Silk Road enabled long-distance dispersal of J. regia from Iran and Trans-Caucasus to Central Asia, and from Western to Eastern China. Ancient commerce also disrupted the local spatial genetic structure of autochthonous walnut populations between Tashkent and Samarkand (Central-Eastern Uzbekistan), where the northern and central routes of the Northern Silk Road converged. A significant association between ancient language phyla and the genetic structure of walnut populations is reported even after adjustment for geographic distances that could have affected both walnut gene flow and human commerce over the centuries. Beyond the economic importance of common walnut, our study delineates an alternative approach for understanding how the genetic resources of long-lived perennial tree species may be affected by the interaction of geography and human history.

Auxin and GTPase activity in membranes from aerobic and anaerobic rice coleoptile

Summary The natural auxin IAA increased the GTPase activity in membrane vesicles prepared from aerobic rice coleoptiles. The effect was evident at short times (30 sec). In membranes from coleoptiles grown in anoxia (a condition in which the tissue is insensitive to auxin) the hormone displayed a weaker effect on GTPase activity. These data, taken together with those previously reported, strongly suggest the involvement of GTP-binding proteins in auxin signal transduction in rice coleoptile.

Rethinking the history of common walnut (Juglans regia L.) in Europe: Its origins and human interactions

Common walnut (Juglans regia L) is an economically important species cultivated worldwide for its high-quality wood and nuts. It is generally accepted that after the last glaciation J. regia survived and grew in almost completely isolated stands in Asia, and that ancient humans dispersed walnuts across Asia and into new habitats via trade and cultural expansion. The history of walnut in Europe is a matter of debate, however. In this study, we estimated the genetic diversity and structure of 91 Eurasian walnut populations using 14 neutral microsatellites. By integrating fossil pollen, cultural, and historical data with population genetics, and approximate Bayesian analysis, we reconstructed the demographic history of walnut and its routes of dispersal across Europe. The genetic data confirmed the presence of walnut in glacial refugia in the Balkans and western Europe. We conclude that human-mediated admixture between Anatolian and Balkan walnut germplasm started in the Early Bronze Age, and between western Europe and the Balkans in eastern Europe during the Roman Empire. A population size expansion and subsequent decline in northeastern and western Europe was detected in the last five centuries. The actual distribution of walnut in Europe resulted from the combined effects of expansion/contraction from multiple refugia after the Last Glacial Maximum and its human exploitation over the last 5,000 years.

Two Putative G-Protein α Subunits Dissociate from Rice Coleoptile Membranes after GTP Stimulation

Summary The antibody raised against an aminoacidic sequence that is conserved among many animal G protein α subunits (anti-α common antibody) recognized some membrane proteins from rice coleoptile on immunoblot. Two of them, showing apparent molecular weights of 28 and 30 kDa, dissociated from aerobic and anoxic coleoptile membranes following GTPγS or GTP stimulation, but not after GDP addition. Furthermore, anti-α common antibody could be used to immunoprecipitate a saturable GTP binding activity from the supernatant of [ 35 S]GTPγS-stimulated membranes, but not after [ 3 H]GDP addition.

Polyamine Spermine Protects Young Pea Plants Against Ultraviolet-C Radiation

ABSTRACT The effects of ultraviolet-C (UV-C) irradiation and polyamine spermine on the content of some stress marker and non-enzymatic antioxidants in leaves of young pea plants were investigated. UV-C irradiation led to a decrease in pea fresh weight, the content of leaf pigments and free proline, accompanied with an increase in malondialdehyde. The initial augmentation in the free thiol levels was transient in UV-C treated plants and finally a substantial decrease was found. Spermine led to a significant augmentation of free thiols and proline content along with a decline in total phenols, but these alterations diminished during the experimental period. Based on comparative analyses of the results obtained for plants treated with UV-C and polyamine, it could be concluded that preliminary application of spermine protects pea plants against irradiation, by maintaining normal plant growth, stabilizing cell membranes and activating non-enzymatic antioxidants.

Biochemical Seed Traits of Camelina sativa – An Emerging Oilseed Crop for Biofuel: Environmental and Genetic Influences

Camelina (Camelina sativa (L.) Crantz) is an attractive alternative and sustainable oilseed crop for multipurpose uses, including as a biofuel feedstock. To evaluate the value of C. sativa in Lombardia (north Italy), seven genotypes were cultivated under different climates of two consecutive years and growing seasons; quality and quantity of seed, oil, and flour were analyzed. Genotypes mainly influenced seed weight (0.98–1.56 g/1000 seeds), protein (245-401 mg/g), glucosinolates, and phytic acid. Oil content (27.5%–37.2%) and fatty acid (FA) composition varied with year and growing season among genotypes. Oils were rich in linolenic and linoleic acids (68.4%–80.8%). The monounsaturated acids ranged from 16.4%–25.6%, although erucic acid was much lower at 4.30%. Saturated FAs represented a small fraction. Low free FAs content (0.01%–0.81%) and different amounts of tocopherols (0.44-2.69 μg/mg) in oils depended on years. Correlations among seed and biochemical traits were found. Genotypes with low protein and high phytic acid contents would not be the best for flour quality. Genotypes showing high levels of protein and C18:3/C18:2 fatty acids ratio could be useful for humans and livestock. Genotype with relatively high C18:1 fatty acid content can be used mainly for biofuel production. Altogether, the data indicated that C. sativa cultivation could be promoted as an economically profitable oilseed crop in north Italian environments.

Endogenous Phytohormones and Germination of Rice Under Anoxia: Indoleacetic Acid and Abscisic Acid

Indole acetic acid (IAA) and abscisic acid (ABA) are present in cereal seeds, and it is believed they play roles in seed maturation and germination. Modification of environmental conditions can inhibit or modify germination and seedling elongation. Our aim is to analyse the role played by IAA and ABA during the anoxic germination of rice (Oryza sativa), the only crop plant able to germinate in the absence of oxygen. Examination of the metabolism of IAA and ABA in rice seeds during the first week of anoxic germination shows that IAA esters are not hydrolysed, while ABA is released rapidly into the growth medium. Comparison of flooding tolerant and intolerant rice cultivars (Japonica and Indica ecotypes respectively) indicates that IAA levels are not closely related to the elongation capacity of the anaerobic coleoptile. However, an ability to excrete ABA may be an adaptative mechanism that enhances the elongation of anaerobic coleoptiles.