Spirostanol saponins of Allium porrum L.

An investigation of the extracts from bulbs of Allium porrum L. has led to the isolation of four spirostanol saponins. Two of them are new compounds and have been identified as: (25R)-5 alpha-spirostan-3 beta, 6 beta-diol 3-O-{O-beta-D-glucopyranosyl-(1-->2)-O-[beta-D-xylopyranosyl-(1-->3)]-O- beta -D-glucopyranosyl-(1-->4)-beta-D-galactopyranoside} (3) and (25R)-5 alpha-spirostan-3 beta,6 beta-diol 3-O-{O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->2)-O- [beta-D-xylopyranosyl-(1-->3)]-O-beta-D-glucopyranosyl-(1-->4)-beta-D- galactopyranoside} (4). The isolated compounds were evaluated for their antifungal activity.     

Chitinase in roots of mycorrhizal Allium porrum: regulation and localization

Chitinase (EC 3.2.1.14) activity was measured in roots of Allium prorrum L. (leek) during development of a vesicular-arbuscular mycorrhizal symbiosis with Glomus versiforme (Karst.) Berch. During the early stages of infection, between 10 and 20 d after inoculation, the specific activity of chitinase was higher in mycorrhizal roots than in the uninfected controls. However, 60–90 d after inoculation, when the symbiosis was fully established, the mycorrhizal roots contained much less chitinase than control roots. Chitinase was purified from A. porrum roots. An antiserum against beanleaf chitinase was found to cross-react specifically with chitinase in the extracts from non-mycorrhizal and mycorrhizal A. porrum roots. This antiserum was used for the immunocytochemical localization of the enzyme with fluorescent and gold-labelled probes. Chitinase was localized in the vacuoles and in the extracellular spaces of non-mycorrhizal and mycorrhizal roots. There was no immunolabelling on the fungal cell walls in the intercellular or the intracellular phases. It is concluded that the chitin in the fungal walls is inaccessible to plant chitinase. This casts doubts on the possible involvement of this hydrolase in the development of the mycorrhizal fungus. However, fungal penetration does appear to cause a typical defense response in the first stages that is later depressed.     

Polygalacturonase activity and location in arbuscular mycorrhizal roots of Allium porrum L.

Polygalacturonase activity and location were analysed in leek roots (Allium porrum L.) colonized by Glomus versiforme (Karst.) Berch, an arbuscular mycorrhizal (AM) fungus. Polygalacturonase activity in mycorrhizal roots did not differ quantitatively from that found in nonmycorrhizal roots on all of the four harvesting dates. Fractionation of mycorrhizal root extracts by ion-exchange chromatography showed that expression of polygalacturonase was specific to the mutualistic association. Immunofluorescence and immunogold experiments were carried out to locate the polygalacturonase in mycorrhizal roots using a polyclonal antibody raised against a Fusarium moniliforme endopolygalacturonase. Immunolabelling was observed all over the arbuscules (intracellular fungal structures) but particularly at the interface between the arbuscule and the plant membrane. Since pectins are located in this area, we suggest that polygalacturonase produced during the symbiosis could play a role in plant pectin degradation.     

Formation of chiasmata in the synchronous meiotic cycle of Lilium longiflorum

The results of treatment of meiotic cells of Lilium longiflorum by cycloheximide at the time of chiasma initiation and formation suggest that in the sequential phases of nuclear development, complete chiasma suppression resulting in achiasmate cells is attained prior to a quantitative reduction of chiasma frequency. Reduction of chiasma frequency and complete suppression are believed to be based on two different mechanisms.     

Partial purification of the acyl-CoA elongase of Allium porrum leaves

Acyl-CoA elongase has been partially purified from leek (Allium porrum L.) epidermal cells. The microsomal elongase is first solubilized by Triton X-100. The solubilized proteins are then submitted to anion exchange chromatography on DEAE-cellulose and, finally, to gel filtration on Ultrogel 34 AcA. The purification of the elongase activity is accompanied by the enrichment in three major protein bands of 59, 61, and 65 kDa. The partially purified elongase is highly delipidated (about 10 mol lipid/mol of 60- to 65-kDa protein) and phosphatidylserine and phosphatidylethanolamine account respectively for 60 and 40% of the remaining phospholipids. The partially purified elongase retains some activities associated with fatty acid biosynthesis. The overall activity is strongly stimulated by the addition of exogenous lipids. In the presence of a mixture of PS, PE, and PC the C18-CoA elongase activity is increased more than sixfold. The Km value of stearoyl-CoA, in the presence of lipid vesicles, was determined to be 1.7 microM.     

A Comparison of Leek (Allium porrum) and Onion (Allium cepa) Seed Development

Leek and onion seed dry weight increased exponentially for thefirst 31 days after flowering (DAF) but thereafter the increasein dry weight was slower. Before maximum seed dry weight wasreached at 45 DAF in onion and 59 to 66 DAF in leek, seed moisturecontent, seed oxygen uptake and conductivity of the seed steepwater fell from initially high levels. Although some seeds germinated31 DAF in both species, full germination in both was not reacheduntil 66–80 DAF. Tolerance of the seed to artificial dryingimmediately after harvesting occurred 45 DAF in onion and 74DAF in leek. Free nuclear division continued in the endospermuntil 17–22 DAF in onion and until 31–35 DAF inleek but it was not until 45 DAF in onion and 66 DAF in leekthat the embryo and endosperm filled the cavity formed by thepericarp. After formation of cell walls in the endosperm thepattern of change in cell number in both species was similar.The shrunken appearance of the seed coat in leek, which occurredearly in seed development, was associated with the period offree nuclear division in the endosperm and, in addition, thepericarp was thinner than in onion. There was no evidence thatthe shrunken seed coat early in development was associated withself as opposed to open-pollination. Allium porrum, Allium cepa, seed development, endosperm, embryo, cell number, germination, respiration, seed leachates     

Expression and localization of polygalacturonase during the outgrowth of lateral roots in Allium porrum L.

The presence of polygalacturonase and its correlation with the formation of lateral roots in leek (Allium porrum L.) seedlings have been investigated. During root growth, a steady increase in polygalacturonase activity was associated with that of the lateral root primordia. Fractionation of root extract by fast protein liquid chromatography resolved at least two polygalacturonase isoforms. One of the isoforms, a 75-kdalton protein, strongly reacted on Western blots probed with a polyclonal antibody raised against tomato polygalacturonase. It also reacted with both polyclonal and monoclonal antisera raised against Fusarium moniliforme polygalacturonase. In situ localization with these three antibodies showed that polygalacturonase was present over the meristems of lateral root primordia. Antibodies against pectins (Knox et al. 1990, Planta 181, 512–521) detected large amounts of pectic material filling the area between the apex of the primordium and the mother root tissues. We suggest that a polygalacturonase plays an important role in leek root morphogenesis, particularly during lateral root outgrowth.Abbreviations FPLC fast protein liquid chromatography - RGU one unit of polygalacturonase activity - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis The Authors are grateful to Dr. Dean Della Penna (Department of Vegetable Crops, University of California, Davis, Calif., USA) for generously providing the polyclonal antibody raised against the tomato polygalacturonase. This research was supported by National Research of Italy, Special project RAISA, Subproject N2, N360.     

Agrobacterium tumefaciens-mediated transformation of leek (Allium porrum) and garlic (Allium sativum)

Transgenic leek (Allium porrum) and garlic (Allium sativum) plants have been recovered by the selective culturing of immature leek and garlic embryos via Agrobacterium-mediated transformation using a method similar to that described by Eady et al. (Plant Cell Rep 19:376–381, 2000) for onion transformation. This method involved the use of a binary vector containing the m-gfp-ER reporter gene and nptII selectable marker, and followed the protocol developed previously for the transformation of onions with only minor modifications pertaining to the post-transformation selection procedure which was simplified to have just a single selection regime. Transgenic cultures were selected for their ability to express the m-gfp-ER reporter gene and grown in the presence of geneticin (20 mg/l). The presence of transgenes in the genome of the plants was confirmed using TAIL-PCR and Southern analysis. This is the first report of leek and true seed garlic transformation. It now makes possible the integration of useful agronomic and quality traits into these crops.     

Field studies of leaf development and expansion in the leek (Allium porrum)

An analysis of leek leaf development and expansion was carried out over three seasons using field-grown plants of three varieties which were directly sown at different dates or transplanted from controlled conditions. In all cases, successive leaves appeared (tip visible) at equal intervals of accumulated temperature. Detailed analysis of a single sowing in 1985 showed that the regularity of leaf appearance was a consequence of the coordinated response to accumulated temperature of leaf initiation (plastochron 100°C days > 0°C) and leaf blade and sheath extension. For each successive leaf, an additional 32°C days were required between initiation and appearance to allow for the linear increase in ‘sheath’ height, giving a phyllochron of 132°C days. Direct measurement of leaf extension before and after leaf appearance, and of the length of the leaf extension zone, confirmed that the rate of leaf extension, in terms of accumulated tempeature, was constant, and independent of leaf number. However, there were differences between seasons and between varieties in the responses of leaf appearance, leaf extension and ‘sheath’ length to accumulated temperature. It was concluded that the simple ontogenetic increase in leaf dimensions, which was a feature of all the crops studied, was a consequence of the progressive increase in the duration of leaf expansion.     

Silver staining two types of meiotic nodules.

We have developed a reliable method for silver staining nodules on synaptonemal complexes (SCs) of tomato (Lycopersicon esculentum). This technique involves hypotonically bursting primary microsporocytes, fixing SC spreads with paraformaldehyde, and incubating the spreads at 40 degrees C in a 33% aqueous silver nitrate solution covered with nylon mesh. When tomato SCs were stained by this method, nodules were observed with the same distribution and frequency as nodules stained with uranyl acetate and lead citrate. Incubation in silver nitrate at higher temperatures caused the loss of some or all nodules. The pattern of loss suggests that two types of nodules coexist during late zygonema and early pachynema and that one type becomes the late nodules of mid-pachynema through early diplonema.     

AFLP marking of the genotypes of leek (Allium porrum) varieties

The results of the AFLP analysis of 16 leek (Allium porrum) accessions and related species of the sections of the genus Allium are presented. Restriction enzymes and primer combinations for the identification of the genotypes of the A. porrum accessions were chosen. As a result, 265 polymorphic AFLP fragments were amplified for 25 analyzed genotypes, and specific spectra of DNA fragments were obtained for each accession. A total of 24 fragments specific for the A. porrum genome was detected, of which only two characterized the genotypes of individual accessions. A wide range of genetic diversity (0.11-0.32) was revealed for the A. porrum varieties and lines used in the analysis. The highest level of similarity in the analyzed set of accessions was found between A. porrum and sand leek (A. scorodoprasum).     

Mitochondrial DNA variation and crossability of leek (Allium porrum) and its wild relatives from the Allium ampeloprasum complex

 Mitochondrial (mt) DNA variation in the cultigens leek, kurrat and prei-anak is limited compared to that of their wild relatives in the Allium ampeloprasum complex. The phylogenetic relationships among these cultigens and their wild relatives is quite close, with the majority of the species clustering within one mitochondrial clade. The presence in leek of an extra-mitochondrial genetic element was noted. Analysis of crossability showed that all species were interfertile with leek. It is suggested that the genetic variation present within the A. ampeloprasum complex could be exploited in order to broaden the genetic basis of leek. Received: 14 August 1996 / Accepted: 23 August 1996     

Meiotic synapsis of the Allium porrum B chromosome: evidence for a derived isochromosome origin.

Ultrastructural analysis of B chromosome synapsis in surface-spread (2B) pollen mother cells of the leek, Allium porrum, has clarified their structural organization and shed new light on their origin. In pachytene cells containing two B chromosomes, these chromosomes either formed a pair of univalents showing foldback hairpin loops or synapsed together to form bivalents of several different types. The synaptic configurations of univalents and bivalents indicate that these B chromosomes have a basically isochromosome organization, but this is modified by a slight centric shift giving an arm ratio of 1.1:1. This analysis adds to the growing number of B chromosomes that have been shown to be isochromosomes or isochromosome derivatives. Key words : Allium porrum, B chromosomes, synapsis, synaptonemal complex, isochromosome.     

C-band proximity of chiasmata and absence of terminalisation in Allium flavum (Liliaceae)

Chiasmata in male meiosis of Allium flavum from early diplotene to metaphase I are found to occur almost exclusively very close to the terminal and intercalary C-bands. Heterozygosity of intercalary C-bands, where one homologue has one band missing, allows the direct proof that chiasmata do not terminalise and therefore mark the point of exchange.     

Determination of antidiabetic activity in Allium cepa (onion) tissue cultures.

Seedling, seedling parts and callus cultures of onion were tested for their antidiabetic activity by feeding the tissue-extracts to diabetic rats. The results indicated much higher antidiabetic activity in callus cultures as compared to natural bulbs of onion. These results may be of pharmaceutical significance since the callus can be used as an alternative source for the isolation of antidiabetic compounds.     

The amino acid sequence of cytochrome c from Allium porrum L. (leek)

The amino acid sequence of leek cytochrome c was determined with 0.4μmol of protein. The sequence was deduced solely from a chymotryptic digest. The cytochrome was homologous with other plant cytochromes c of mitochondrial origin. Leek cytochrome c has an N-acetylated `tail' as compared with mammalian cytochrome c, and two residues of ε-N-trimethyl-lysine. Unlike other plant cytochromes c, leek cytochrome c has glutamic acid or glutamine in position 11, leucine in position 20 and alanine in position 51. 4-Hydroxyproline partially substitutes for proline in position 79. Experimental details are given in a supplementary paper that has been deposited as Supplementary Publication SUP 50012, at the National Lending Library for Science and Technology, Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1973) 131, 5.