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Recombinam DNA technologies offer new methods of detecting animal diversity at various levels. DNA »fingerprinting« using cloned repetitive sequences can be used to distinguish between individuals within breeds and may thus be used for paternity testing (Jeffreys et al. 1985). The forensic value of evidence of this kind has given guarded approval by the UK Immigration Advisory Service in its annual report (Nature 1987). At the between-species level labeled total genomic DNA was used by Durnam et al. (1985) as probe in an in situ hybridization for speciesverification of chromosomal materials in human-rodent hybrid cell lines, and we recently described the use of .sup.3H-labeled genomic pig DNA probe for detection af swine chromosomes in swine-hamster hybrid cell lines (Thomsen & Christensen 1986).

▪ Abstract  The timing of the transition from vegetative to reproductive development is of great fundamental and applied interest but is still poorly understood. Recently, molecular-genetic approaches have been used to dissect this process in Arabidopsis. The genetic variation present among a large number of mutants with an early- or late-flowering phenotype, affecting the control of both environmental and endogenous factors that influence the transition to flowering, is described. The genetic, molecular, and physiological analyses have led to identification of different components involved, such as elements of photoperception and the circadian rhythm. Furthermore, elements involved in the signal transduction pathways to flowering have been identified by the cloning of some floral induction genes and their target genes.

The genus Citrus , comprising some of the most widely cultivated fruit crops worldwide, includes an uncertain number of species. Here we describe ten natural citrus species, using genomic, phylogenetic and biogeographic analyses of 60 accessions representing diverse citrus germ plasms, and propose that citrus diversified during the late Miocene epoch through a rapid southeast Asian radiation that correlates with a marked weakening of the monsoons. A second radiation enabled by migration across the Wallace line gave rise to the Australian limes in the early Pliocene epoch. Further identification and analyses of hybrids and admixed genomes provides insights into the genealogy of major commercial cultivars of citrus. Among mandarins and sweet orange, we find an extensive network of relatedness that illuminates the domestication of these groups. Widespread pummelo admixture among these mandarins and its correlation with fruit size and acidity suggests a plausible role of pummelo introgression in the selection of palatable mandarins. This work provides a new evolutionary framework for the genus Citrus . The origin, evolution and domestication of Citrus and the genealogy of the most important wild and cultivated citrus varieties. When life gave us lemons Citrus fruits are one of the most cultivated crops worldwide, yet the evolutionary relationships among citrus species remain uncertain. Daniel Rokhsar, Manuel Talon and colleagues analyse the genomes of 60 accessions that represent a diverse range of citrus species, including 30 newly sequenced citrus genomes. They characterize the diversity and evolution of citrus at the species level and identify interspecific citrus hybrids and admixtures—genetic mixing between previously isolated populations—that could be the result of human activities such as migration and agriculture. The authors identify 10 progenitor species and suggest that citrus originated in southeast Asia, diversifying during the late Miocene epoch through a rapid southeast Asian radiation that correlated with a changing climate, including the weakening of the monsoons. They also find extensive relatedness among mandarins and sweet oranges, showing a complex history of admixture during the domestication of these groups.

A characteristic feature of fish is the wide physiological range of blood parameters and also the large individual variations. The aim of this study was to compare the haematological profile, glucose and lactate levels of four teleost fish species (Gobius niger, Mugil cephalus, Sparus aurata, Dicentrarchus labrax) and to establish the similarities and differences between these species which are widely present in the Tyrrhenian Sea. To this end, glucose, lactate and complete haematological profiles were determined for 25 fish from each species. Statistical analysis confirmed statistical differences in blood parameters among the four species. Our findings show a lower level of glucose and higher levels of lactate, red blood cells and haemoglobin in M. cephalus with respect to the other species. White blood cell and thrombocyte counts have the same trend and result higher in S. aurata. The differences found in this study can be attributed to the feeding behaviour, life style and adaptation of the different fish species to the habitat in which they dwell.

During oil deposition in developing seeds of Arabidopsis, photosynthate is imported in the form of carbohydrates into the embryo and converted to triacylglycerols. To identify genes essential for this process and to investigate the molecular basis for the developmental regulation of oil accumulation, mutants producing wrinkled, incompletely filled seeds were isolated. A novel mutant locus, wrinkled1 (wri1), which maps to the bottom of chromosome 3 and causes an 80% reduction in seed oil content, was identified. Wild-type and homozygous wri1 mutant plantlets or mature plants were indistinguishable. However, developing homozygous wri1 seeds were impaired in the incorporation of sucrose and glucose into triacylglycerols, but incorporated pyruvate and acetate at an increased rate. Because the activities of several glycolytic enzymes, in particular hexokinase and pyrophosphate-dependent phosphofructokinase, are reduced in developing homozygous wri1 seeds, it is suggested that WRI1 is involved in the developmental regulation of carbohydrate metabolism during seed filling

Single, double, and triple null combinations of Arabidopsis mutants lacking the photoreceptors phytochrome (phy) A (phyA-201), phyB (phyB-5), and cryptochrome (cry) 1 (hy4-2.23n) were examined for de-etiolation responses in high-fluence red, far-red, blue, and broad-spectrum white light. Cotyledon unhooking, unfolding, and expansion, hypocotyl growth, and the accumulation of chlorophylls and anthocyanin in 5-d-old seedlings were measured under each light condition and in the dark. phyA was the major photoreceptor/effector for most far-red-light responses, although phyB and cry1 modulated anthocyanin accumulation in a phyA-dependent manner. phyB was the major photoreceptor in red light, although cry1 acted as a phyA/phyB-dependent modulator of chlorophyll accumulation under these conditions. All three photoreceptors contributed to most blue light deetiolation responses, either redundantly or additively; however, phyB acted as a modulator of cotyledon expansion dependent on the presence of cry1. As reported previously, flowering time in long days was promoted by phyA and inhibited by phyB, with each suppressing the other's effect. In addition to the effector/modulator relationships described above, measurements of hypocotyls from blue-light-grown seedlings demonstrated phytochrome activity in blue light and cry1 activity in a phyAphyB mutant background

The global genetic diversity of cassava and related Manihot species is revealed by sequencing of 53 cultivated and wild accessions and genotyping of 268 African cassavas, providing a vital resource for breeding. Cassava ( Manihot esculenta ) provides calories and nutrition for more than half a billion people. It was domesticated by native Amazonian peoples through cultivation of the wild progenitor M. esculenta ssp. flabellifolia and is now grown in tropical regions worldwide. Here we provide a high-quality genome assembly for cassava with improved contiguity, linkage, and completeness; almost 97% of genes are anchored to chromosomes. We find that paleotetraploidy in cassava is shared with the related rubber tree Hevea , providing a resource for comparative studies. We also sequence a global collection of 58 Manihot accessions, including cultivated and wild cassava accessions and related species such as Ceará or India rubber ( M. glaziovii ), and genotype 268 African cassava varieties. We find widespread interspecific admixture, and detect the genetic signature of past cassava breeding programs. As a clonally propagated crop, cassava is especially vulnerable to pathogens and abiotic stresses. This genomic resource will inform future genome-enabled breeding efforts to improve this staple crop.

Lignin, a complex phenolic polymer, is important for mechanical support, water transport, and defense in vascular plants. Compressive strength and hydrophobicity of xylem cell walls are imparted by the lignin polymer, which is deposited during the terminal differentiation of tracheids and other cell types. The resistance of xylem to compressive stresses imposed by water transport and by the mass of the plants is important to growth and development. In addition, the insolubility and complexity of the lignin polymer makes it resistant to degradation by most microorganisms. Therefore, lignin serves an important function in plant defense. Variation in lignin content, composition, and location is likely to affect these essential processes. The constraints on the amount, composition, and localization of lignin for normal xylem function and plant defense are not known. Lignin composition, quantity, and distribution also affect the agroindustrial uses of plant material. Digestibility and dietary conversion of herbaceous crops are affected by differences in lignin content and composition (Akin et al., 1986, 1991). Lignin is an undesirable component in the conversion of wood into pulp and paper; removal of lignin is a major step in the paper making process. Furthermore, the resistance of lignin to microbial degradation enhances its persistence in soils. Lignin is, therefore, a significant component in the global carbon cycle. The mechanisms of control of lignin composition and quantity have wide implications regarding the adaptation and evolution of land plants and provide a basis for improved genetic manipulation of lignin for agroindustrial end uses. In this Update, we will focus on the levels of control of lignin variation, including (a) metabolic control, (b) regulation of individual enzymes in the biosynthetic pathway, and (c) regulation of gene expression.

Japanese Spanish mackerel Scomberomorus niphonius is a commercially important species in the East China Sea and Yellow Sea, but there is limited knowledge of its genetic population structure. In order to detect its genetic structure, sequence variation of the first hypervariable segment of the control region was analyzed among eight populations of S. niphonius from the East China Sea and Yellow Sea. A total of 119 polymorphic sites were detected in the 505-bp segment of the control region among 134 individuals of S. niphonius, defining 112 haplotypes. Mean haplotype diversity and nucleotide diversity for the eight populations were 0.9963+-0.0017 and 0.0236+-0.0119, respectively. As expected, analysis of molecular variance detected no significant differences at all hierarchical levels, and most of the conventional population Phisub(ST) statistics were negative, indicating that no significant population genetic structure exists in the East China Sea and Yellow Sea. Moreover, the exact test of differentiation supported the null hypothesis that S. niphonius within the East China Sea and Yellow Sea constitutes a panmictic mtDNA gene pool. Neutrality tests and mismatch distribution revealed that S. niphonius underwent population expansion in the late Pleistocene. Strong dispersal capacity of larvae and adults, long-distance migrations, and ocean currents in the studied area could be the reasons for genetic homogeneity in this species in the East China Sea and Yellow Sea. Insufficient time to accumulate genetic variation might be another explanation for the lack of genetic structure in the East China Sea and Yellow Sea.

Grapevine fanleaf virus (GFLV), responsible for fanleaf degeneration, one of the most severe virus diseases of grapevines worldwide, causes substantial crop losses, reduces fruit quality and shortens longevity of grapevines. GFLV is transmitted from grapevine to grapevine by the ectoparasitic nematode Xiphinema index and belongs to genus Nepovirus, family Comoviridae. Since the discovery of the nematode vector in the late _50s and the identification of GFLV as the agent of fanleaf degeneration in the early _60s, a wealth of information was accumulated on its transmission, biological properties and serological characteristics, as well as on structure and expression of GFLV genome. Although dissemination of virus through propagation material has been drastically reduced over the past two decades by implementing rigorous certification schemes and establishing quarantine facilities, effective strategies are still needed to control GFLV in vineyards. Recently, significant progress has been made on the elucidation of the functions of most GFLV proteins, in particular the ones involved in critical steps of virus multiplication cycle, including RNA replication, cell-to-cell movement and transmission by X. index. New insights have also been gained into population structure and genomic variability among isolates from naturally infected vineyards, which have opened new pathways for designing alternative control strategies. This review article offers a comprehensive overview of the most significant advances made over the past 15 years on GFLV and discusses novel control strategies for one of the major threats to grapevine industry worldwide [Il Virus della foglia a ventaglio della vite (GFLV), responsabile della degenerazione a ventaglio, una delle più gravi malattie della vite a livello mondiale, causa rilevanti perdite produttive, riduce la qualità dell'uva e la longevità delle piante. Il GFLV viene trasmesso dal nematode ectoparassita Xiphinema index e appartiene al genere Nepovirus, famiglia Comoviridae. Dalla scoperta del vettore alla fine degli anni '50 e dall'identificazione del GFLV come agente della degenerazione a ventaglio nei primi anni '60, sono state accumulate molte informazioni su trasmissione, proprietà biologiche, caratteri sierologici e struttura ed espressione del genoma del GFLV. Sebbene la diffusione del virus col materiale di moltiplicazione sia stata ridotta drasticamente negli ultimi venti anni con rigorosi schemi di certificazione e strutture per la quarantena, sono tuttora necessarie strategie efficaci per il controllo del GFLV. Recentemente sono stati conseguiti progressi significativi sul chiarimento delle funzioni della maggior parte delle proteine del GFLV, in particolare quelle coinvolte nei passaggi critici del ciclo di moltiplicazione, comprendenti la replicazione dell'RNA, il movimento da cellula a cellula e la trasmissione tramite X. index. Sono state inoltre acquisite nuove informazioni sulla struttura e variabilità genomica delle popolazioni negli isolati provenienti da vigneti infetti naturalmente, che hanno aperto nuove strade per mettere a punto strategie di controllo alternative. Questa rassegna offre un panorama dei progressi più significativi conseguiti negli ultimi 15 anni sul GFLV e discute le strategie innovative di controllo di una delle maggiori minacce per la viticoltura mondiale]