Isolation and expression analysis of low temperature-induced genes in white poplar (Populus alba)

Poplar is an important crop and a model system to understand molecular processes of growth, development and responses to environmental stimuli in trees. In this study, we analyzed gene expression in white poplar (Populus alba) plants subjected to chilling. Two forward suppression-subtractive-hybridization libraries were constructed from P. alba plants exposed to low non-freezing temperature for 6 or 48 h. Hundred and sixty-two cDNAs, 54 from the 6-h library and 108 from the 48-h library, were obtained. Isolated genes belonged to six categories of genes, specifically those that: (i) encode stress and defense proteins; (ii) are involved in signal transduction; (iii) are related to regulation of gene expression; (iv) encode proteins involved in cell cycle and DNA processing; (v) encode proteins involved in metabolism and energetic processes; and (vi) are involved in protein fate.Different expression patterns at 3, 6, 12, 24, 48 h at 4 °C and after a recovery of 24 h at 20 °C were observed for isolated genes, as expected according to the class in which the gene putatively belongs. Forty-four of 162 genes contained DRE/LTRE cis-elements in the 5′ proximal promoter of their orthologs in Populus trichocarpa, suggesting that they putatively belong to the CBF regulon. The results contribute new data to the list of possible candidate genes involved in cold response in poplar.     

Distribution, movement and availability of Cd and Zn in a dredged sediment cultivated with Salix alba

Willows occur as volunteer vegetation on sediment-derived soils, such as dredged sediments, landfill cover or stockpile deposits, and are used as phytoremediators on such soils. The present study evaluates growth and metal uptake by Salix alba grown on a contaminated dredge sediment for 209 days under greenhouse conditions. At the end of the study, the aerial parts of the S. alba plants had grown to heights of between 80 and 117 cm. Biomass and Cd and Zn concentration in the roots, stems and leaves, at 70, 112 and 209 days, showed that Cd and Zn had been bioaccumulated, especially in the leaves.At the three sampling dates, Cd and Zn extractability and pH measurements were also carried out on samples of two soil layers (0–15 and 15–30 cm) from both the planted and the control pots. Cd and Zn extractability were assessed using single extraction procedures (0.01 M CaCl₂; 1 M HNO₃; CaCl₂–TEA–DTPA). The two metals showed similar variations in CaCl₂ and HNO₃ extractabilities, but this was not the case for DTPA extractability. The greatest variations were observed in the upper soil layers of the control pots. In the planted pots, the CaCl₂ extractability of Zn decreased in the upper layer, and the HNO₃ extractability of Zn increased in the lower layer. The pH of the upper soil layer was always higher than the pH of the bottom layer. In addition, we monitored several parameters of the percolates from both the planted and the control sediments, including pH, Eh, conductivity, dissolved organic carbon, Zn and Cd concentrations, and presence of certain cations/anions. Dissolved organic carbon, and Cd and Zn concentrations increased steadily over time. There were no significant differences between the planted and the control pots. After 209 days, the characteristics of the control sediment reflected the effects of ageing in that the CaCl₂-extractable Cd and Zn concentrations had decreased compared with the initial concentrations. Conversely, the concentrations of HNO₃-extractable Cd and Zn had increased. A fraction of the metal initially extracted by CaCl₂ (considered as exchangeable) became less available with time. After 112 days, the plants had extracted approximately 2.8 mg of Zn. At the same time, the CaCl₂ extractability of Zn in the upper, rooted layer decreased by 2.6 mg. We can assume that S. alba extracted Zn from the pool of CaCl₂-extractable Zn.     

Die FormenkreiseMyrmecocichla nigra undarnotti

Ohne Zusammenfassung     

Physiological responses of black willow (Salix nigra) cuttings to a range of soil moisture regimes

We quantified the physiological responses of black willow to four soil moisture regimes: no flooding (control, C), continuous flooding (CF), periodic flooding (PF), and periodic drought (PD). Stomatal limitation was one of the factors that led to the reduced photosynthetic capacity in CF cuttings. Under PD, stomatal closure, decreased leaf chlorophyll content, and increased dark fluorescence yield contributed to photosynthetic decline. CF cuttings accumulated the lowest shoot biomass while the final height and root growth were most adversely affected by PD. PF cuttings tended to allocate more photoassimilates to root growth than to shoots.This revised version was published online in March 2005 with corrections to the page numbers.     

Spatio-temporal variations of functional groups in a Populus nigra L. entomocenosis in the Mitidja plain (Algeria)

This study presents the first data describing the communities of insects and arachnida colonizing 4 aerial compartments of Populus nigra. In terms of temporal variation and total abundance, the analyses show that the communities are structurally and functionally different. It also appears that the taxonomic richness of the communities, and partly their temporal distribution, change according to the gradient of the energy and defense resources under the effect of seasonal variations. The highest species richness recorded on the leaves compartment is due to the amplitude of histo-physiological modifications observed throughout the growing season. To cite this article: Z.-E. Djazouli et al., C. R. Biologies 332 (2009).     

Patterns of parasitoid-host associations in differentially parasitized macrolepidopteran assemblages on Black Willow Salix nigra (Marsh) and Box Elder Acer negundo L.

Studies on the interactions between species co-occurring on a plant and their parasitoids have primarily focused on assemblages or communities of endophytic herbivores. Less is known about assemblages of exophytic herbivores such as lepidopteran species. This study focuses on the interactions among species in macrolepidopteran assemblages on box elder and black willow trees, and their parasitoids. Specifically, we determined how percent parasitism varied within and across species and families of both macrolepidopteran herbivores and their parasitoids. Parasitism by species in all parasitoid families varied across families of macrolepidoptera. However, in general mean yearly percent parasitism was highest among larvae in the box elder assemblage. Braconids were the most abundantly represented parasitoid taxon, however, the contribution that parasitoid families made to total parasitism of all larvae also varied depending on the host tree species. There was no significant correlation between the number of species in a macrolepidopteran family collected on either tree species and levels of parasitism. Mean parasitoid species load for all species was 4.3, a value lower than reported in other studies. There was no significant difference in mean parasitoid species load across families. Similarly, there was no significant difference in average parasitoid loads of macrolepidoptera on box elder and black willow.Bisher waren Untersuchungen über Interaktionen zwischen Arten, die gemeinsam auf einer Pflanze vorkommen, und ihren Parasitoiden in erster Linie auf Ansammlungen oder Lebensgemeinschaften endophytischer Herbivoren fokussiert. Über die Ansammlungen exophytischer Herbivore wie Schmetterlingsarten ist weniger bekannt. Diese Untersuchung konzentriert sich auf die Interaktionen zwischen Arten in Ansammlungen von Makrolepidoptera auf Eschen-Ahorn- und Schwarzweiden-Bäumen und ihren Parasitoiden. Insbesondere bestimmten wir, wie die prozentuale Parasitierung innerhalb der Arten und zwischen Arten und Familien sowohl bei den makrolepidopteren Herbivoren und als auch ihren Parasitoiden variierte. In allen Parasitoiden-Familien unterschied sich die Parasitierung auf Artniveau zwischen den Familien der Makrolepidoptera. Im Allgemeinen war jedoch die mittlere jährliche prozentuale Parasitierung bei Larven in der Ansammlung aufEschen-Ahorn am höchsten. Die Braconiden repräsentierten das parasitoide Taxon mit der größten Abundanz. Der Anteil, den parasitoide Familien am gesamten Parasitismus aller Larven hatten, variierte jedoch ebenfalls in Abhängigkeit von der Art des Wirtsbaumes. Es gab keine signifikante Korrelation zwischen der Anzahl der Arten in einer makrolepidopteren Familie, die auf der jeweiligen Baumart gesammelt wurde, und dem Grad der Parasitierung. Die mittlere Belastung mit parasitoiden Arten war bei allen Arten 4.3, ein geringerer Wert als in anderen Studien berichtet wird. Es gab keinen signifikanten Unterschied zwischen den Familien in den mittleren parasitoiden Belastungen. Ebenso gab es keinen signifikanten Unterschied in den durchschnittlichen parasitoiden Belastungen der Makrolepidoptera auf Eschen-Ahorn und Schwarzweide.     

A large scale survey of Populus nigra presence and genetic introgression from non-native poplars in Switzerland based on molecular identification

Populus nigra is considered a rare and threatened tree species in Switzerland because of dramatic habitat loss owing to river regulations during the last two centuries and because of potential gene introgression from non-indigenous P. deltoides through planted P. x canadensis hybrids. The significance of introgression as an endangerment to P. nigra, however, is controversial. The aims of the present study were (1) to assess how abundant P. nigra trees are in Switzerland and (2) to assess potential gene introgression. We present data from a molecular survey of 1372 putative P. nigra trees from Switzerland, using both chloroplast DNA and nuclear DNA markers. The results show that P. nigra is more abundant in Switzerland than hitherto thought. Furthermore, we detected a low frequency of gene introgression.     

Cadmium tolerance and accumulation in eight potential energy crops

The production of energy crops that can be used for biodiesel production is a sustainable approach for the removal of metal pollutants by phytoremediation. This study investigated the cadmium (Cd) accumulation and tolerance of eight potential energy crops. After growth for 28 days in substrates containing 0, 50, 100 or 200 mg Cd·kg^− 1, seedlings were evaluated for growth parameters, chlorophyll content, chlorophyll fluorescence parameters and Cd accumulation. All eight crops were moderately tolerant to Cd toxicity, with four [i.e., hemp (Cannabis sativa), flax (Linum usitatissimum), castor (Ricinus communis) and peanut (Arachis hypogaea)] being more tolerant than the others. Three of these crops (hemp, flax and peanut) had higher Cd accumulation capacities. The roots of peanut and hemp had high bioconcentration factors (BCF > 1000), while flax shoots accumulated a higher concentration of Cd (> 100 mg/kg). These results demonstrate that it is possible to grow energy crops on Cd-contaminated soil. Hemp, flax and peanut are excellent candidates for phytoremediation.     

Dihydrochalcones, coumarins and alkaloids from Metrodorea nigra

Two novel dihydrochalcones, 2′,3,4′,6′-tetrahydroxy-4-methoxy-3′,5-di-(3,3-dimethylallyl)-dihydrochalcone and 2′,.3,6′-trihydroxy-4-methoxy-5-(3,3-dimethylallyl)-3′,4′-(2″,2″-dimethyldihydropyran)-dihydrochalcone, have been isolated from fresh fruits of Metrodorea nigra. Stems and leaves showed a similar composition and we have isolated common steroids, simple coumarins, several furocoumarins, furoquinoline alkaloids and a furofuran lignan. From stems, we have also isolated the pentacyclic 6-C-monoterpenyl-5,7-dioxycoumarin, deoxybruceol. Structures of the isolated compounds were elucidated on the basis of spectral data.     

馒头柳对镉的耐性、运输途径和累积特征

采用液体培养法研究了馒头柳对镉的耐性、运输过程及富集特征,结果表明:馒头柳具有较强的耐镉特性,水培营养液中镉浓度为0.2 mg·L-1时,镉对柳的生长仍有促进作用;镉从根到地上部的长距离运输具有明显的韧皮部运输特征,表现为植株顶部组织镉含量显著高于底部(P<0.05),韧皮部高于木质部(14倍);馒头柳地上部对镉有非常强的持续富集能力;地上部富集的镉占植株吸收总镉量的52%～62%,且主要集中在叶片,只要秋季清除地表落叶,即可达到清除土壤镉的目的;因此,馒头柳适宜用作镉污染土壤的修复.     

Glycosylation-mediated phenylpropanoid partitioning in Populus tremuloides cell cultures

Background  

Phenylpropanoid-derived phenolic glycosides (PGs) and condensed tannins (CTs) comprise large, multi-purpose non-structural carbon sinks in Populus. A negative correlation between PG and CT concentrations has been observed in several studies. However, the molecular mechanism underlying the relationship is not known.     

Cadmium tolerance and accumulation in Indian mustard is enhanced by overexpressing gamma-glutamylcysteine synthetase

To investigate rate-limiting factors for glutathione and phytochelatin (PC) production and the importance of these compounds for heavy metal tolerance, Indian mustard (Brassica juncea) was genetically engineered to overexpress the Escherichia coli gshI gene encoding gamma-glutamylcysteine synthetase (gamma-ECS), targeted to the plastids. The gamma-ECS transgenic seedlings showed increased tolerance to Cd and had higher concentrations of PCs, gamma-GluCys, glutathione, and total non-protein thiols compared with wild-type (WT) seedlings. When tested in a hydroponic system, gamma-ECS mature plants accumulated more Cd than WT plants: shoot Cd concentrations were 40% to 90% higher. In spite of their higher tissue Cd concentration, the gamma-ECS plants grew better in the presence of Cd than WT. We conclude that overexpression of gamma-ECS increases biosynthesis of glutathione and PCs, which in turn enhances Cd tolerance and accumulation. Thus, overexpression of gamma-ECS appears to be a promising strategy for the production of plants with superior heavy metal phytoremediation capacity.     

Interactions of Microbotryum violaceum (ustilago violacea) with its host plant Silene alba

Sex expression in Silene alba is determined genetically but can be changed in female plants upon infection with the heterobasidiomycete Microbotryum violaceum. This change is not caused by steroids, the classical plant growth regulators, nor by a diffusible morphogen produced and secreted by the fungus. Nor is the production of stamnes in genotypically female flowers caused by the transmission, incorporation and expression of a fungal plasmid since plants regenerated from diseased tissue of genotypically female S. alba did not yield stamen-producing flowers. Neither density gradient centrifugation nor agarose gel electrophoresis of endonuclease restricted DNA from M. violaceum revealed the presence of a plasmid. Southern blots of DNA from S. alba probed with labeled DNA of M. violaceum, however, indicated the presence of homologous, unique sequences absent in non-host plants. Since the same homologous sequences were identified in male and female S. alba, these DNA fragments are not homologous to the coding sequences for male sex expression in S. alba unless they represent genetic elements of the hypothetical gyndyioecious precursor. Two other aspects of the S. alba-M. violaceum interaction have yielded interesting results. M. violaceum grows as sporidia outside of the host, but as short hyphae in planta. The switch from sporidial to hyphal growth is mediated in vitro by hyphal growth factors (HGFs) isolated from aqueous host plant extracts as well as by -tocopherol. In addition to changing the fungal growth form. HGFs may serve as host recognition factors. Siderophore mutants of M. violaceum that accumulated less rhodotorulic acid than wild type also showed reduced or no pathogenicity, indicating that siderophores are an important factor in the host-pathogen interaction.     

Expression profiles of two novel lipoxygenase genes in Populus deltoides

In the present study, we cloned two lipoxygenase genes, PdLOX1 and PdLOX2 (GenBank accession no. DQ131178, DQ131179), from Populus deltoides cv. ‘Lux’ (I-69/55). A prokaryotic expression analysis of PdLOX1 and PdLOX2 revealed that the encoded exogenous proteins were identical to the predicted molecular weights and possessed the expected lipoxygenase activities. Chromatogram analysis indicated that the two lipoxygenase mainly possess 13-LOX activity. Phylogenetic analysis of the derived amino acid sequences of known lipoxygenases revealed that PdLOX1 and PdLOX2 were members of the type 2 13-LOX family of genes. This class of lipoxygenases is known to be involved in biotic and abiotic stress. Using real-time RT-PCR, we evaluated PdLOX1 and PdLOX2 expression following exposure to a Poplar fungal pathogen (Marssonina brunnea f. sp. Multigermtubi), mechanical injury, methyl jasmonate (MeJA), or salicylic acid (SA). We report that both PdLOX1 and PdLOX2 expression levels were increased following exposure to M. brunnea f. sp. Multigermtubi, with the pathogen exerting a relatively stronger influence on PdLOX1 expression. Furthermore, expression levels of the two genes were also up-regulated by mechanical damage and exposure to MeJA. In contrast, both PdLOX1 and PdLOX2 expression was down-regulated by SA treatment. We propose that the two novel lipoxygenases may play an important role in Poplar resistance to biotic and abiotic stress.     

Beobachtungen an der Schleiereule,Tyto alba, in Surinam

Ohne Zusammenfassung