Microsatellites from kousa dogwood (Cornus kousa)

Microsatellite loci were identified from Cornus kousa'National'. Primer pairs for 86 loci were developed and of these, eight were optimized and screened using genomic DNA from 22 kousa cultivars. All optimized loci were polymorphic and the number of alleles per locus ranged from three to 17. Observed heterozygosity ranged from 0 to 0.3 and expected heterozygosity ranged from 0.38 to 0.91. These microsatellites will be useful in population studies, and a breeding programme for cultivar development of Cornus species.     

Molecular evolution of PISTILLATA-like genes in the dogwood genus Cornus (Cornaceae)

The MADS-box gene family encodes critical regulators determining floral organ development. Understanding evolutionary patterns and processes of MADS-box genes is an important step toward unraveling the molecular basis of floral morphological evolution. In this study, we investigated the evolution of PI-like genes of the MADS-box family in the dogwood genus Cornus (Cornaceae). Cornus is a eudicot lineage in the asterids clade, and is intriguing in evolving petaloid bract morphology in two major lineages within the genus. The gene genealogy reconstructed using genomic DNA and cDNA sequences suggests multiple PI-like gene duplication events in Cornus. An ancient duplication event resulted in two ancient paralogs, CorPI-A and CorPI-B, which have highly diverged intron regions. Duplication of CorPI-A further resulted in two paralogs in one subgroup of Cornus, the BW group that does not produce modified bracts. Most species analyzed were found to contain more than one copy of the PI-like gene with most copies derived recently within species. Estimation and comparison of dN/dS ratios revealed relaxed selection in the PI-like gene in Cornus in comparison with the gene in the closely related outgroups Alangium and Davidia, and in other flowering plants. Selection also differed among major gene copies, CorPI-A and CorPI-B, and among different morphological subgroups of Cornus. Variation in selection pressures may indicate functional changes in PI-like genes after gene duplication and among different lineages. Strong positive selection at three amino acid sites of CorPI was also detected from a region critical for dimerization activity. Total substitution rates of the CorPI gene also differ among lineages of Cornus, showing a trend similar to that found in dN/dS ratios. We also found that the CorPI-A copy contains informative phylogenetic information when compared across species of Cornus.     

五种国产Lai木属（广义）植物的核型

对分布于我国的Lai木属Cornus L.(广义）4个主要类群的5种植物进行了细胞学研究。结果表明,这5种植物的染色体数目和核型分别为：灯台树C.controversa Hemsl.2n=20=2m 8sm 10st;红瑞木C.alba L.2n=22=8sm 12st 2t;毛Lai C.waltari Wanger.2n=22=8sm 14st(0-2SAT);山茱萸C.officinalis Seib.et Zucc.2n=18-8m 10sm(0-2SAT);四照花（变种）C.kousa var.chinensis Osborn 2n=22=2sm 6st(0-2SAT) 14t.     

Evolutionary patterns in the antR-Cor gene in the dwarf dogwood complex (Cornus, Cornaceae)

The evolutionary pattern of the myc-like anthocyanin regulatory gene antR-Cor was examined in the dwarf dogwood species complex (Cornus Subgenus Arctocrania) that contains two diploid species (C. canadensis and C. suecica), their putative hybrids with intermediate phenotypes, and a tetraploid derivative (C. unalaschkensis). Full-length sequences of this gene (∼4 kb) were sequenced and characterized for 47 dwarf dogwood samples representing all taxa categories from 43 sites in the Pacific Northwest. Analysis of nucleotide diversity indicated departures from neutral evolution, due most likely to local population structure. Neighbor-joining and haplotype network analyses show that sequences from the tetraploid and diploid intermediates are much more strongly diverged from C. suecica than from C. canadensis, and that the intermediate phenotypes may represent an ancestral group to C. canadensis rather than interspecific hybrids. Seven amino acid mutations that are potentially linked to myc-like anthocyanin regulatory gene function correlate with petal colors differences that characterize the divergence between two diploid species and the tetraploid species in this complex. The evidence provides a working hypothesis for testing the role of the gene in speciation and its link to the petal coloration. Sequencing and analysis of additional nuclear genes will be necessary to resolve questions about the evolution of the dwarf dogwood complex.     

Fruit set,fruit reduction,and fruiting strategy in Cornus sanguinea (Cornaceae)

We studied various aspects of the fruiting biology of Cornus sanguinea (Cornaceae), a fleshy-fruit-producing deciduous shrub, in four populations in northwest Spain. One population was studied over a 5-yr period (1989-1994), and the remaining populations in 1994 only. Fruit-set level varied among years (range 11-18%) and among populations (range 8-22%), but was in all cases low. Within plants, fruit-set level did not vary significantly among inflorescences, indicating that inflorescence fruit set is independent of inflorescence position and inflorescence, phenology. To investigate the function of surplus flowers, we carried out flower removal experiments. Inflorescence fruit-set level was unaffected by removal of up to =75% of flowers. These results suggest that Cornus sanguinea regulates its fruit-set level via plasticity in the number of fruits aborted: if flower mortality has been high, fewer fruits will be aborted. Within the inflorescence, surplus flowers thus act as insurance against flower loss.     

Phylogeny-based developmental analyses illuminate evolution of inflorescence architectures in dogwoods (Cornus s. l., Cornaceae)

? Inflorescence architecture is important to angiosperm reproduction, but our knowledge of the developmental basis underlying the evolution of inflorescence architectures is limited. Using a phylogeny-based comparative analysis of developmental pathways, we tested the long-standing hypothesis that umbel evolved from elongated inflorescences by suppression of inflorescence branches, while head evolved from umbels by suppression of pedicels. ? The developmental pathways of six species of Cornus producing different inflorescence types were characterized by scanning electron microscopy (SEM) and histological analysis. Critical developmental events were traced over the molecular phylogeny to identify evolutionary changes leading to the formation of umbels and heads using methods accounting for evolutionary time and phylogenetic uncertainty. ? We defined 24 developmental events describing the developmental progression of the different inflorescence types. The evolutionary transition from paniculate cymes to umbels and heads required alterations of seven developmental events occurring at different evolutionary times. ? Our results indicate that heads and umbels evolved independently in Cornus from elongated forms via an umbellate dichasium ancestor and this process involved several independent changes. Our findings shed novel insights into head and umbel evolution concealed by outer morphology. Our work illustrates the importance of combining developmental and phylogenetic data to better define morphological evolutionary processes.     

A two-generation analysis of pollen pool genetic structure in flowering dogwood, Cornus florida (Cornaceae), in the Missouri Ozarks

Anthropogenic landscape change can disrupt gene flow. As part of the Missouri Ozark Forest Ecosystem Project, this study examined whether silvicultural practices influence pollen-mediated gene movement in the insect-pollinated species, Cornus florida L., by comparing pollen pool structure (Φ(st)) among clear-cutting, selective cutting, and uncut regimes with the expectation that pollen movement should be least in the uncut regime. Using a sample of 1500 seedlings-10 each from 150 seed parents (43 in clear-cut, 74 in selective, and 33 in control sites) from six sites (each ranging from 266 to 527 ha), eight allozyme loci were analyzed with a pollen pool structure approach known as TwoGener (Smouse et al., 2001; Evolution 55: 260-271). This analysis revealed that pollen pool structure was less in clear-cut (Φ(C) = 0.090, P < 0.001) than in uncut areas (Φ(U) = 0.174, P < 0.001), with selective-cut intermediate (Φ(S) = 0.125, P < 0.001). These estimates translate into more effective pollen donors (N(ep)) in clear-cut (N(ep) = 5.56) and selective-cut (N(ep) = 4.00) areas than in uncut areas (N(ep) = 2.87). We demonstrate that Φ(C) ≤ Φ(S) ≤ Φ(U), with Φ(C) significantly smaller than Φ(U) (P < 0.034). The findings imply that, as long as a sufficiently large number of seed parents remain to provide adequate reproduction and to avoid a genetic bottleneck in the effective number of mothers, silvicultural management may not negatively affect the effective number of pollen parents, and hence subsequent genetic diversity in Cornus florida.     

中华青荚叶的一个新果糖酯

从山茱萸科中华青荚叶( Helwingia chinensis )的乙醇提取物中分离得到一个新果糖酯和十个已知化合物.通过现代波谱技术分别鉴定为:2- O -(E)-咖啡酰-3- O -(3, 5-二甲氧基香豆酰)-α-D-呋喃果糖甙(1),2- O -β-D-呋喃果糖基α-D-异吡喃糖酯(2),甘草甜素(3),4′-羟基-7- O -葡萄糖-2, 3-二羟黄酮甙(4),黄豆甙(5),5-葡萄糖芹菜甙(6),7- O -葡萄糖芹菜甙(7),4- O -葡萄糖香豆酸(8), 葡萄糖咖啡酸(9), 3β-赤杨醇(10), 薯蓣皂甙3- O -{α-L-鼠李糖吡喃糖基(1→2)-[α-L-阿拉伯呋喃糖基(1→3)]-β-D-葡萄糖吡喃糖} (11).     

中华青荚叶的一个新环烯醚萜甙

从山茱萸科中华青荚叶（Helwingia chinensis）的乙酸乙酯部份分离得到一个新环烯醚萜和三个已知环烯醚萜化合物,通过现代波谱技术,确定其结构为10-O-trans—cinnamoyl。leoside（1）,10-hydroxyoleoside 11-methylester（2）,jasminoside（3）and 10-hydroxyoleumpein（4）。     

Micropropagation of flowering dogwood (Cornus florida) from seedlings

A method for regenerating whole plants from nodal (axillary bud) cultures of seedlings was developed for flowering dogwood (Cornus florida L.). The seed source significantly influenced the rate of proliferation, although cultures initiated from each of the seven mother trees produced some shoots. Woody plant medium (WPM) was superior to either Murashige and Skoog or Schenk and Hildebrandt basal medium. 6-Benzyladenine (BA) at 2.2 or 4.4 m stimulated the generation of significantly more useable shoots (1 cm) compared to all other concentrations (0.5–22.5 m tested. Thidiazuron (TDZ) at 0.6 and 1.1 m supported proliferation, but strongly inhibited shoot elongation. TDZ initiated cultures transferred to medium containing 4.4 m BA produced usable shoots after five additional subcultures. Shoots generated adventitious roots when exposed to either a 12-h pulse of relatively high concentrations (246–1230 m or continuous lower concentrations (0.5–49.0 m of indolebutyric acid (IBA) for longer periods. Microshoots produced the significantly greatest number of roots when subjected to 4.9 m IBA in WPM over a 4-week period. Whole plants were acclimatized to the laboratory conditions and subsequently to the greenhouse. The methodology described here should be useful in a breeding program by supplying multiple copies of unique, recombinant genotypes.     

Phenotypic Plasticity of Sylleptic Branching: Genetic Design of Tree Architecture

The crown of many trees is composed of a main axis and branches. All branches arise from axillary or lateral buds and two types of branches exist: proleptic and sylleptic. Proleptic branches form from buds that have undergone a rest period, typically associated with winter dormancy, whereas sylleptic branches emerge without a rest and without complete bud formation. All trees have proleptic branches; some trees with the indeterminant growth habit have both proleptic and sylleptic branches. Sylleptic branches may play an important role in determining tree growth, architecture and adaptation for many temperate-zone woody plants. We review evidence for the phenotypic plasticity of sylleptic branches and its genetic, environmental, and developmental control.     

Physiological responses of dogwood (Cornus florida) to infestation by the dogwood borer (Thamnosphecia scitula)

Studies of a healthy dogwood tree ( Cornus florida ) and one suffering from a chronic infestation of Thamnosphecia scitula revealed some physiological responses of dogwood to insect damage. In high light the stomatal resistances, measured with a diffusion porometer, of leaves from the infested tree were more than double those of leaves from the healthy tree, indicating that the stomata were not open as wide in the infested tree. The greater stomatal resistance and the curling of leaves from the infested tree implied a deficiency of water, but measurements with a pressure chamber revealed only slight differences in dehydration between the two trees. Furthermore, the leaf curling was not relieved by allowing infested leaves to absorb water and attain full turgor. Leaves from the infested tree contained 35 % more reducing sugars and 63 % more sucrose, but only about half the nitrogen and ash of the healthy counterparts. Photosynthesis was significantly depressed, but dark respiration was not modified in leaves of infested compared with healthy trees. Leaves from the infested tree were 85 % as large and exhibited a 35 % greater specific leaf weight than those from the healthy tree. The conductance of water by stems from the infested tree was only 61–78 % of that by the healthy tree. It is suggested that the inferred disruption of the vascular system by insect activity alters the distribution of minerals and metabolites, hastens senescence and stomatal closure, and modifies growth by diminishing stem conductance, slowing photosynthesis, reducing leaf area, and changing leaf morphology.