w4-Mutable line in soybean

An unstable mutation for anthocyanin pigmentation in soybean (Giycine max [L.] Merr.) was identified in 1983. The mutability is conditioned by an allele at the w4 locus that is recessive to wild type. The population containing the mutable allele is known as the w4-mutable line. Most plants in the line have chimeric flowers with purple sectors on a near-white background. The mutable allele yields germinal revertants at a rate that varies from 5 to 10% per generation, and the revertant alleles are stable. Approximately 1% of the progenies derived from germinal revertant plants contain mutations at other loci These features, as well as the occurrence of pale flower phenotypes and changes of state, suggest that a transposable element system is producing the unstable phenotype. Several new mutants were isolated in an experiment designed to tag loci. The first three chlorophyll-deficient mutants found (CD-1, CD-2, and CD-3) are inherited as single-gene recessives. Each of the mutants lacks the same two mitochondrial malate dehydrogenase (MDH) bands. No recombination has been detected between the MDH phenotype and the chlorophyll-deficient phenotype. Genetic data indicate that the three mutants are allelic, and additional evidence suggests that each of the CD mutants is the result of a deletion. In the CD-1, CD-2, and CD-3 mutants, the deletions result in the silencing of an MDH locus, atypical chloroplast development, and an altered chlorophyll composition. Additional mutants for root necrosis, partial and near sterility, chlorophyll deficiency, and flower color isolated from the transposon tagging study have provided material for future research.     

Eucalyptus stomata with occluded anterior chambers

Summary This paper describes variations of a mode of stomatal development already described in a species (E. orbifolia) ofEucalyptus L'Herit. (Carr andCarr, Protoplasma 96, 127, 1978) in which the outer part of the stomatal pore (ostiole) is formed by the creation of a break in the thin layer of cuticle lying over the stomatal chamber. In a number of species with a thick cuticle (e.g., E. cooperana) the process of breakthrough is different: additions to the guard cell upper thickenings extend from them as ridges, pressing the leaf cuticle outwards. Breakthrough of the cuticle occurs above the tips of these extensions. The anterior chamber is lined throughout by the extensions, which become heavily cutinized. This mode of stomatal development is typical of many other species of eucalypts, including those dealt with in this paper.In addition, inE. halophila thickenings develop on the end walls of the anterior chamber above the unusual upturned poles of the guard cells. Cutinized thickenings, pseudo-outer stomatal ledges are also formed on the upper guard cell walls. All these wall thickenings occlude the anterior chamber, leaving only a narrow passage in the form of a letter H.Similar occlusions are found inE. balladoniensis but here the thickenings are developed into the chamber from its lateral walls. InE. gracilis, and the related speciesE. celastroides andE. calycogona, less regular occluding thickenings develop principally from the lateral walls of the chamber. In addition, large pseudo-outer stomatal ledges may be formed.These phenomena are discussed in terms of the mechanism underlying the formation of the occluding thickenings and the possibility of their adaptive significance.     

Excision of an Active CACTA-Like Transposable Element From DFR2 Causes Variegated Flowers in Soybean [Glycine max (L.) Merr.]

Active endogenous transposable elements, useful tools for gene isolation, have not been reported from any legume species. An active transposable element was suggested to reside in the W4 locus that governs flower color in soybean. Through biochemical and molecular analyses of several revertants of the w4-m allele, we have shown that the W4 locus encodes dihydroflavonol-4-reductase 2 (DFR2). w4-m has arisen through insertion of Tgm9, a 20,548-bp CACTA-like transposable element, into the second intron of DFR2. Tgm9 showed high nucleic acid sequence identity to Tgmt*. Its 5′ and 3′ terminal inverted repeats start with conserved CACTA sequence. The 3′ subterminal region is highly repetitive. Tgm9 carries TNP1- and TNP2-like transposase genes that are expressed in the mutable line, T322 (w4-m). The element excises at a high frequency from both somatic and germinal tissues. Following excision, reinsertions of Tgm9 into the DFR2 promoter generated novel stable alleles, w4-dp (dilute purple flowers) and w4-p (pale flowers). We hypothesize that the element is fractured during transposition, and truncated versions of the element in new insertion sites cause stable mutations. The highly active endogenous transposon, Tgm9, should facilitate genomics studies specifically that relate to legume biology.IN soybean [Glycine max (L.) Merr.], five loci W1, W3, W4, Wm, and Wp control the pigmentations in flowers and hypocotyls (Palmer et al. 2004). Soybean plants with genotype W1_ w3w3 W4_ Wm_ Wp_ produce wild-type purple flowers (Figure 1) and purple hypocotyls. Mutations at the W4 locus in the W1_ background result in altered pigment accumulation patterns in petals and reduced levels of purple pigments in flowers and hypocotyls. Four mutant alleles, w4, w4-m, w4-dp, and w4-p have been mapped to this locus. The w4 allele represents a spontaneous mutation, which produces near-white flowers (Figure 1) and green hypocotyls (Hartwig and Hinson 1962; Groose and Palmer 1991). The w4-m allele was identified from a cross between two experimental breeding lines with white and purple flowers, respectively (Palmer et al. 1989; Weigelt et al. 1990). w4-m is characterized by variegated flowers (Figure 1) and green hypocotyls with purple sectors (Groose et al. 1988).Open in a separate windowFigure 1.—Variation in flower color among soybean lines carrying different W4 alleles.w4-m has been proposed to harbor a class II transposable element (Palmer et al. 1989). Presumably, somatic excision of the putative transposable element results in the variegated (Groose et al. 1988) and germinal excision wild-type phenotypes, purple flowers and purple pigments on hypocotyls (Palmer et al. 1989; Groose et al. 1990). The mutable line carrying w4-m undergoes germinal reversion at a very high frequency, about 6% per generation (Groose et al. 1990). Approximately 1% of the progeny derived from germinal revertants contain new mutations in unlinked loci, presumably resulting from reinsertion of the element (Palmer et al. 1989). For example, female partial-sterile 1 (Fsp1), female partial-sterile 2 (Fsp2), female partial-sterile 3 (Fsp3), and female partial-sterile 4 (Fsp4) were isolated from progenies of germinal revertants with purple flowers and were mapped to molecular linkage groups (MLG) C2, A2, F, and G, respectively (Kato and Palmer 2004). Similarly, 36 male-sterile, female-sterile mutants mapped to the st8 region on MLG J (Kato and Palmer 2003; Palmer et al. 2008a), 24 necrotic root (rn) mutants mapped to the rn locus on MLG G (Palmer et al. 2008b), and three Mdh1-n y20 mutants, mapped to a chromosomal region on MLG H (Palmer et al. 1989; Xu and Palmer 2005b), were isolated among progenies of germinal revertants.In addition to germinal revertants with purple flowers, the w4 mutable line also generated intermediate stable revertants that produce flowers with variable pigment intensities ranging from purple to near-white (Figure 1). Two stable intermediate revertants, w4-dp and w4-p, are allelic to W4. Plants carrying w4-dp or w4-p alleles produce dilute purple flowers or pale flowers, respectively (Figure 1) (Palmer and Groose 1993; Xu and Palmer 2005a).Pigment formation requires two types of genes: structural genes that encode anthocyanin biosynthetic enzymes [e.g., CHS (chalcone synthase), F3H (flavanone 3-hydroxylase), DFR (dihydroflavonol-4-reductase), ANS (anthocyanidin synthase); Figure S1] and regulatory genes that control expression of structural genes (Holton and Cornish 1995). Among the five genes, W1, W3, W4, Wp, and Wm, controlling pigment biosynthesis in soybean, four have been characterized at the molecular level (Figure S1). W1 encodes a flavonoid 5′, 3′-hydroxylase (Zabala and Vodkin 2007). W3 cosegregates with a DFR gene, Wp encodes a flavonone 3-hydroxylase (F3H), and Wm encodes a flavonol synthase (FLS) (Fasoula et al. 1995; Zabala and Vodkin 2005; Takahashi et al. 2007).Nine CACTA-type class II transposable elements, Tgm1, Tgm2, Tgm3, Tgm4, Tgm5, Tgm6, Tgm7, Tgm-Express1, and Tgmt*, have been reported in soybean (Rhodes and Vodkin 1988; Zabala and Vodkin 2005, 2008). Tgm-Express1 causes mutation in Wp (Zabala and Vodkin 2005) and Tgmt* ({"type":"entrez-nucleotide","attrs":{"text":"EU190440","term_id":"158514866","term_text":"EU190440"}}EU190440) in T that encodes a flavonoid 3′ hydroxylase (F3′H) (Zabala and Vodkin 2003, 2008). The objectives of the present study were to characterize the W4 locus and then investigate whether the w4-m allele harbors an active transposable element. Our results showed that a CACTA-like transposable element located in a dihydroflavonol-4-reductase gene causes variegated flower phenotype in soybean.     

Effects of supplied cinnamic acids and biosynthetic intermediates on the anthocyanins accumulated by wild carrot suspension cultures

Anthocyanins isolated and characterized from the wild carrot suspension cultures used here were 3-O--D-glucopyranosyl-(16)-[-D-xylopyranosyl-(12)-]-D<-galactopyranosylcyanidin (1), 3-O-[-D- xylopyranosyl-(12)--D-galactopyranosyl]cyanidin (2), 3-O-(6-O-sinapoyl)--D-glucopyranosyl-(16)-[-D- xylopyranosyl-(12)-]-D-galactopyranos ylcyanidin (3), 3-O-(6-O-feruoyl)--D-glucopyranosyl-(16)-[- D-xylopyranosyl-(12)-]-D-galactopyranosylcyanidin (4), 3-O-(6-O-coumaroyl)--D-glucopyranosyl-(16)- [-D-xylopyranosyl-(12)-]-D-galactopyrano sylcyanidin (5), 3-O-[6-O-(3,4,5-trimethoxycinnamoyl)]-- D-glucopyranosyl-(16)-[-D-xylopyranosyl-(12)-]-D-galactopyranosylcyanidin (6), 3-O-[6-O-(3,4-dime- thoxycinnamoyl)]--D-glucopyranosyl-(16)-[-D-xylopyranosyl-(12)-]-D-galactopyranosylcyanidin (7), 3-O-[(6-O-sinapoyl)--D-glucopyranosyl-(16)--D-galactopyranosyl]cyanidin (8), and 3-O-(-D-galactopyranosyl)cyanidin (9). Except when cinnamic acids were provided in the culture medium, the major anthocyanin present in the two clones examined was 2. When the naturally occurring and some non-naturally occurring cinnamic acids were provided individually in the medium, 1 and 2 were minor components and the anthocyanin acylated with the supplied cinnamic acid, namely 3, 4, 5, 6, or 7 was the major anthocyanin present in the tissue. When caffeic acid was provided the major anthocyanin in the tissue was 4, thereby suggesting that the caffeic acid was methylated before its use in anthocyanin biosynthesis. Other cinnamic acids supplied had limited effects on the anthocyanins accumulated and appeared not to result in the accumulation of new anthocyanins by the tissue. Thus the tissue can use some but not all analogues of sinapic acid to acylate anthocyanins. Additional anthocyanins were detected in extracts of the wild carrot tissue cultures using mass spectrometry (both MS/MS and HPLC/MS). The additional compounds detected have also been found in cultures of black carrot, an Afghan cultivar of Daucus carota ssp. sativa and the flowers of wild carrot giving no evidence for qualitative differences in the anthocyanins synthesized by subspecies, cell cultures from subspecies, or clones from cell cultures. There are major differences in the amounts of individual anthocyanins found in cultures from different subspecies and in different clones from cell cultures. Here anthocyanins without acyl groups were usually found in the tissues and their accumulation is discussed. On the basis of the structures of the isolated anthocyanins, a likely pathway from cyanidin to the accumulated anthocyanins is proposed and discussed.Abbreviations Sin sinapoyl - Fer feruoyl - 4-Coum. 4-coumaroyl - 3,4-MeO₂Cin 3,4-dimethoxyeinnamoyl - 3,4,5-MeO₃Cin 3,4,5-trimethoxycinnamoyl - Cya cyanidin     

Purification and characterization of two intracellular β-glucosidases from the Neurospora crassa mutant cell-1

Two intracellular -glucosidases (E.C. 3.2.1.21) were purified from the filamentous fungus Neurospora crassa, mutant cell-1 (FGSC no. 4335) and characterized. The extent of purification were 2.55- and 28.89-fold for -glucosidase A and -glucosidase B, respectively. -Glucosidase A was a dimeric protein, and B a monomeric protein, with molecular masses of 178 and 106 kDa, respectively. Both isoenzymes were glycoproteins with relatively high carbohydrate contents (-glucosidase A, 29.2%; -glucosidase B, 34.2%). The isoelectric points determined by IEF were 6.27 and 4.72, respectively. pH optima for activity were determined to be 5.0 and 5.5, and temperature optima to be 55 and 60 °C, for -glucosidases A and B, respectively. Both purified -glucosidases. especially -glucosidase B, showed relatively high stability against pH and temperature. Both enzymes were stable in the pH range of 5.0–9.0. The activities were completely retained up to 48 h at temperatures below 40 °C. At higher temperatures, enzymes were relatively unstable and lost their activities at 60 °C after 24 h. Both -glucosidases were highly activated by CuCl₂, and inhibited by SnCl₂ and KMnO₄. Hg²⁺ and Ag⁺ also inhibited severely -glucosidase B. The K _m and V _max values of the isoenzymes against cellobiose as substrate were 1.50 mM and 12.2mol min^–1 mg^–1 for -glucosidase A and 2.76 mM and 143.5 mol min^–1 mg^–1 for -glucosidase B.     

Molecular characterization of rDt, a maize transposon of the “Dotted” controlling element system

Summary We have molecularly cloned the rDt transposon, one component of the classic Dotted two-element system of controlling elements. The rDt transposon was identified as a DNA insertion in each of two independent mutation events of the maize A1 gene, a gene necessary for the biosynthesis of anthocyanin pigment. Both mutant alleles result in a stable, anthocyaninless phenotype in all plant tissues. When the transposon Dotted, (Dt), is present in the genome each allele exhibits a characteristic mutable phenotype (spots of anthocyanin pigmentation). The DNA insertion has been designated rDt, for it responds to or is regulated by the Dt element to allow expression of the otherwise mutated gene, and it had not been named in earlier genetic studies. Sequence analysis revealed the rDt element to be an identical 704 bp insertion within the two mutable alleles, but in opposite orientation and in different exons of the gene. rDt contains an imperfect terminal inverted repeat with similarity to transposable elements of various species. A duplication of 8 bp of the target host site is formed upon integration of the element, and the element is excised from the locus in a germinal revertant. The difference in phenotype of the two unstable alleles, a1 and am-1:Cache, is discussed.     

Effects of low-efficiency pollinators on plant fitness and floral trait evolution in <Emphasis Type="Italic">Campanula americana</Emphasis> (Campanulaceae)

Floral visitors vary in their pollination efficiency and their preferences for floral traits. If low-efficiency pollinators decrease the amount of pollen available to higher efficiency visitors, then low-efficiency visitors may actually have negative fitness consequences for the plants that they visit. We used experimental arrays in two populations to determine the floral preferences and the fitness effects of low-efficiency (or ugly) pollinators on Campanula americana. These ugly pollinators (halictid bees) preferentially visited flowers with pollen over flowers that had had their pollen removed. C. americana pollen color varies quantitatively from light tan to dark purple, and we found that natural variation in pollen color influenced the magnitude of halictid preferences for flowers with pollen. In general, preferences for flowers with pollen were stronger when the ugly pollinators foraged in arrays of flowers with tan-colored pollen than in arrays with purple-colored pollen. When plants received few visits by efficient Bombus pollinators, visits by ugly pollinators significantly decreased siring success relative to plants where visits by ugly pollinators were prevented. In contrast, ugly pollinators did not influence siring success when higher efficiency pollinators were more abundant. Thus, the relationship between low-efficiency pollinators and the plants that they visit varies from commensalistic to antagonistic depending on the presence of other pollinators in the community. Our findings suggest that the negative fitness effects and floral preferences of low-efficiency or ugly pollinators may contribute to the maintenance of a pollen color polymorphism in C. americana.     

Amaranthin in feather cockscombs is synthesized via glucuronylation at the cyclo-DOPA glucoside step in the betacyanin biosynthetic pathway

Uridine 5-diphosphate (UDP)-glucuronic acid: cyclo-DOPA 5-glucoside glucuronosyltransferase activity was detected in a crude extract prepared from the purple flowers of feather cockscombs. This suggests that the glucuronic acid moiety of amaranthin and its derivatives may be introduced at the cyclo-DOPA glucoside step, but not at the betanidin glucoside step.     

Effect of gibberellic acid on pod set in soybean

Field-grown soybean plants (Glycine max (L.) Merr. cv. Evans) were treated with gibberellic acid (GA₃; 10gl^–1) and/or (2-chloroethyl)-trimethylammonium chloride (CCC; 0.8gl^–1) in 1983 and 1984, and subsequent anthesis, pod set, seed size, seed number, and seed yield were determined at one node. The treatments were applied to five leaves in the center of each plant (typically leaves 7–11) and reproductive development at the node in the center of those leaves was monitored. Gibberellin A₃ applied Early (about 3d before anthesis of the first flower at the monitored node) had no effect on the number of flowers produced, but decreased the fraction of flowers that set pods in both experimental years (by 32% in 1983 and 76% in 1984). Seed size was slightly decreased by the GA₃ treatment in 1983 but not in 1984. The Middle GA₃ treatment (applied about 3 days after the Early treatment) slightly decreased the number of pods set; and Late treatments (9 days after) had no effect. None of the monitored parameters were affected by CCC.The Early experiments were repeated with two additional genotypes, Lincoln and T210. Genotype T210 is a single-gene, dwarf mutant of Lincoln whose stem elongation and leaf expansion are insensitive to GA₃. Gibberellin A₃ affected the reproductive parameters in Lincoln very similarly to Evans but those in T210 were unaffected. This indicates that GA₃ exerts its effect by increasing the mass of vegetative tissue and thus diverting assimilates away from the pods. However, since the mutation in T210 might affect a receptor that is in flowers as well as shoots, it is possible that GA₃ exerted its effect on the normal genotypes directly on the developing pods, rather than indirectly by diverting photoassimilates.     

Structure of a new nonasaccharide isolated from human milk: VI2Fuc,V4Fuc,III3Fuc-p-lacto-N-hexaose

The structure of a new nonasaccharide isolated from human milk has been investigated. By using methylation analysis, FAB-MS and¹H-and¹³C-NMR spectroscopy as basic methods of structural investigation, this oligosaccharide was identified as VI²--Fuc,V⁴-Fuc,III³--Fuc-p-lacto-n-hexaose: Fuc1-2Gal1-3[Fuc1-4]GlcNAc1-3Gal1-4[Fuc1-3]GlcNAc1-3Gal1-4Glc.Abbreviations COSY correlation spectroscope - DP degree of polymerisation - FAB-MS fast atom bombardment-mass spectrometry - HPLC high performance liquid chromatography - NMR nuclear magnetic resonance - GLC gas-liquid chromatography     

Production of a novel syrup containing neofructo-oligosaccharides by the cells of Penicillium citrinum

A novel syrup containing neofructo-oligosaccharides was produced from sucrose (Brix 70) by whole cells of Penicillium citrinum. The efficiency of fructo-oligosaccharides production was more than 55% and those of the main carbohydrate components, 1-kestose (Fruf 21Fruf 21 Glc), nystose (Fruf 21Fruf 21 Fruf 21 Glc) and neokestose (Fruf 26 Glc12 Fruf), were 22, 14 and 11%, respectively.     

Structures of the carbohydrate units of polysialoglycoproteins isolated from the eggs of four species of salmonid fishes

Fish egg polysialoglycoprotein (PSGP) is a novel type of 200 kDa-glycoprotein containing more than 50% sialic acid by weight and about 90O-glycosidically-linked sialoglycan units per molecule. Of about 100 different molecular species assumed to be present in a sialoglycan mixture obtained by alkaline borohydride treatment ofSalvelinus leucomaenis pluvius PSGP, 23 mono- to tetrasialylglycans were isolated by anion-exchange chromatography and preparative column chromatography on porous silica, and their structures were determined. Core asialo-oligosaccharides were obtained from PSGP of four species of salmonid fishes by exhaustive enzymatic desialylation of sialoglycan mixtures and the structures of purified compounds were determined. Two complete types of asialopentasaccharide core structures, Fuc1-3GalNAc1-3Gal1-4 Gal1-3GalNAcOL, and GalNAc1-4GalNAc1-3Gal1-4Gal1-3GalNAcOL, and all of the possible biosynthetic precursors of these pentasaccharide cores were found in every PSGP examined. All types of oligosaccharide chains, both complete and incomplete, were found to occur in highly sialylated forms in PSGP.Abbreviations NeuAc N-acetylneuraminic acid - NeuGc N-glycolylneuraminic acid - GalNAcOL N-acetylgalactosaminitol - PSGP polysialoglycoprotein - SRO sialidase-resistant oligosaccharide     

Pollination biology of two species ofKielmeyera (Guttiferae) from Brazilian cerrado vegetation

The pollination biology and breeding systems ofKielmeyera coriacea andK. speciosa, two sympatric woody species common in the cerrado vegetation of C. Brazil, were studied. Both species have similar nectarless, polystemonous Papaver-type flowers which are visited by a similar spectrum of insects, though they bloom in different seasons and are thus phenologically isolated. Large carpenter bees seem to be the most important pollinators and these and other bees effect buzz pollen retrieval despite the fact that anthers are not poricidal. Both species ofKielmeyera possess strong xenogamous breeding systems. The presence of staminate flowers and andromonoecy inK. coriacea, as well as the longevity ofK. speciosa flowers are discussed as alternative strategies to improve pollination success and reproductive efficacy.     

Studies on Tn951 (lac+) expression in Agrobacterium

Summary None of the Agrobacterium tumefaciens and A. rubi strains tested produces detectable amounts of -galactosidase although they are capable of utilizing lactose as sole source of carbon. This opportunity was taken to investigate the expression of lac transposon Tn951 (Cornelis et al. 1978) in Agrobacterium with the ultimate goal of using this system to investigate alien gene expression. When the transposon was introduced with the help of a broad-host range plasmid, RP1, the transconjugants produced significant quantities of -galactosidase which was inducible by isopropyl--D-thiogalactopyranoside. Tn951 was capable of restoring the Lac⁺ phenotype to an A. tumefaciens mutant not capable of using lactose. Cellobiose, a known inducer of aldohexopyranoside: cytochrome c oxidoreductase which regulates the characteristic 3-ketolactose production in Agrobacterium: van Beeumen and De Ley (1968), had no effect on -galactosidase activity.Abbreviations NCPPB National Collection of Plant Pathogenic Bacteria, Harpenden - km kanamycin resistance - str streptomycin resistance - rif ^r rifampicin resistance     

Promotion of hyphal growth in Ustilago violacea by host factors from Silene alba

Ustilago violacea specifically parasitizes susceptible members of the Caryophyllaceae. We isolated water-soluble compounds from leaves of Silene alba which promoted hyphal development in the dimorphic pathogen. We also isolated hyphal growth promoting -tocopherol from S. alba. The water-soluble activity, which we term hyphal growth factor, or HGF, separated into four bands with gel filtration chromatography and represented over 40% of the total hyphal growth promoting activity isolated from S. alba. The water-soluble HGF activity may be host-specific and may function as a determinant of the host-parasite specificity between U. violacea and caryophyllaceous host plants.Abbreviations HGF Hyphal growth factor - BHT butylated hydroxytoluene     

Fluorescent banding pattern analysis of eight taxa of Phaseolus and Vigna in relation to their phylogenetic relationships

Phylogenetic relationships among eight taxa of seven species of Phaseolus and Vigna (Phaseolus angularis, P. aureus, P. calcaratus, P. coccineus, P. vulgaris, Vigna sesquipedalis and V. sinensis; 2n = 22 each) were studied by the fluorescent chromosome banding technique. Preparations of somatic metaphase chromosomes of each taxon were sequentially stained with Giemsa, GC-specific fluorochrome chromomycin A₃ (CMA) and AT-specific fluorochrome 4-6-diamidino-2-phenylindole (DAPI). On the basis of the fluorescent banding patterns of the 22 chromosomes of each taxon, P. angularis, P. coccineus (from China and Korea) and P. vulgaris were grouped into one group (Phaseolus group), P. aureus and two Vigna species were grouped into another (Vigna group) and P. calcaratus was grouped in an independent group.     

Flora Palinologica Italiana,Sezione Aeropalinologica: S 205 -Pinus pinea L. (Pinaceae)

Summary According to the program Palynological Italian Flora, Aeropalynological section, the pollen morphological card ofPinus pinea L. is presented. The study is carried out on pollen coming from three Italian localities and regards fresh and acetolyzed pollen. For each sample, measurements are carried out on 30 fresh pollen grains in glicerol jelly with fuchsin and on 30 acetolyzed pollen grains in water/glicerol (1/1); general observations regard 1000 fresh and 1000 acetolyzed pollen grains/sample. Some observations on the main differences between fresh and acetolyzed pollen are mentioned.

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Riassunto Nell'ambito della Flora Palinologica Italiana, Sezione Aeropalinologica, è presentata la scheda morfopalinologica diPinus pinea L. nella versione su polline fresco e polline acetolizzato, su tre campioni di diversa provenienza. Vengono notate le principali differenze tra polline fresco e polline acetolizzato.

     

Genetic mapping in (<Emphasis Type="Italic">Populus tomentosa</Emphasis> ×<Emphasis Type="Italic"> Populus bolleana</Emphasis>) and<Emphasis Type="Italic"> P. tomentosa</Emphasis> Carr. using AFLP markers

The AFLP genetic linkage maps for two poplar cultivars were constructed with the pseudo-test-cross mapping strategy. The hybrids were derived from an interspecific backcross between the female hybrid clone TB01 (Populus tomentosa × Populus bolleana) and the male clone LM50 (P. tomentosa). A total of 782 polymorphic fragments were obtained with a PCR-based strategy using 49 enzyme-nested (EcoRI/MseI) primer combinations. Six hundred and thirty two of these fragments segregated in a 1:1 ratio (P<0.01), indicating that these DNA polymorphisms are heterozygous in one parent and null in the other. The linkage analysis was performed using Mapmaker version 3.0 with LOD 5.0 and a maximum recombination fraction () of 0.3. Map distances were estimated using the Kosambi mapping function. In the framework map for LM50 (P. tomentosa), 218 markers were aligned in 19 major linkage groups. The linked loci spanned approximately 2,683 cM of the poplar genome, with an average distance of 12.3 cM between adjacent markers. For TB01 (P. tomentosa × P. bolleana), the analysis revealed 144 loci, which were mapped to 19 major linkage groups and covered about 1,956 cM, with an average distance of 13.6 cM between adjacent markers. These maps covered about 87% and 77% of the estimated genome size of parents LM50 and TB01, respectively. The maps developed in this study lay an important foundation for future genomics research in poplar, providing a means for localizing genes controlling economically important traits in P. tomentosa.Communicated by O. Savolainen     

Significance of flower exploding pollination on the reproduction of the Scotch broom, <Emphasis Type="Italic">Cytisus scoparius</Emphasis> (Leguminosae)

The significance of single flower visits by pollinators on the reproductive success of the Scotch broom, Cytisus scoparius, with explosive flowers was investigated. Unexploded flowers (intact flowers) produced no fruit, implying that autonomous selfing and apomixis do not occur and that the explosion of flowers by insects is necessary for the fertilization of flowers. The fruit set in the natural condition was intermediate between that in artificial selfing or exploding and that in artificial outcrossing. Seed set and the ratio of seeds to ovules did not differ significantly between the natural condition and artificial outcrossing. The fruit set by a single flower visit from Apis mellifera was similar to natural conditions. Apis mellifera was the most frequent visitor and the number of flowers tripped open per hour was the highest among all the flower visitors. Approximately 75% of pollen on a flower disappeared in a single flower visit by A.mellifera. The small amount of pollen remaining on already-exploded flowers appears to be the reason why A.mellifera do not frequently visit already-exploded flowers. The higher seed set by outcrossing was believed to contribute to the seed set in both natural conditions and single flower visits by A.mellifera, and did not differ between them. Therefore, at least in Japan, A.mellifera appears to be the most important pollinator for C.scoparius, resulting in a high outcrossing rate with each single flower visit.     

Alfalfa transposable elements and variegation

Alfalfa with unstable anthocyanin pigmentation has been independently discovered on six occasions since 1958. Genetic studies showed that each of the six unstable stocks was due to an allele mutable at the basic anthocyanin locus C2 in alfalfa. The alleles are designated c2-m1 through c2-m6. Variegated phenotypes of m1, m2, and m3 are similar and express reversion from the recessive to the dominant state. This reversion produces streaks and sectors of pigment in flower petals and seeds that are otherwise white. Reversion occurs at various times in development and may result in periclinal chimeras. The c2-m4 allele is unique in that it arose during tissue culture, whereas the other mutables were discovered in plant populations. Interestingly, m4 is very stable in planta and only rarely produces a sectored flower, but is very unstable in vitro as measured by about 23% revertant plants regenerated from tissue cultures. Most m4 reversion occurs relatively early in development and results in completely pigmented in vitro revertants, and in large sectors on in planta revertants. Alleles m5 and m6 are phenotypically and genetically similar. Their flowers are basic purple with white streaks thus representing mutation from dominant purple to recessive white. White progeny of m5 and m6 are very stable both in planta and in vitro; reversion of white to purple was never observed. Thus, the loss of function of the dominant allele results in a stable recessive or a deficiency. The absolute stability of m5 white derivatives favors the deficiency model, because transposable element mutations might show reversion. Finally, several mutations are described that reoccur in the mutable populations. It is speculated that they are recent mutations due to transposition of transposable elements.