Expression of a carrot 36 kD antifreeze protein gene improves cold stress tolerance in transgenic tobacco

Antifreeze proteins （AFPs） enable organisms to survive under cold conditions, and have great potential in improving cold tolerance of cold-sensitive plants, In order to determine whether expression of the carrot 36 kD antifreeze protein gene confers improved cold-resistant properties to plant tissues, we tried to obtain transgenic tobacco plants which expressed the antifreeze protein. Cold, salt, and drought induced promoter Prd29A was cloned using PCR from Arabidopsis. Two plant expression vectors based on pBI121 were constructed with CaMV35S：AFP and Prd29A：AFP. Tobacco plantlets were transformed by Agrobacterium-medicated transformation. PCR and Southern blotting demonstrated that the carrot 36 kD afp gene was successfully integrated into the genomes of transformed plantlets. The expression of the afp gene in transgenic plants led to improved tolerance to cold stress. However, the use of the strong constitutive 35S cauliflower mosaic virus （CaMV） promoter to drive expression of afp also resulted in growth retardation under normal growing conditions. In contrast, the expression of afp driven by the stress-inducible Prd29A promoter from Arabidopsis gave rise to minimal effects on plant growth while providing an increased tolerance to cold stress condition （2℃）. The results demonstrated the prospect of using Prd29A-AFP transgenic plants in cold-stressed conditions that will in turn benefit agriculture.     

Overexpression of mtlD gene in transgenic Populus tomentosa improves salt tolerance through accumulation of mannitol

The mtlD gene encoding mannitol-1-phosphate dehydrogenase, which catalyzes the biosynthesis of mannitol from fructose, was cloned from Escherichia coli and transferred to poplar (Populus tomentosa Carr.) through Agrobacterium-mediated transformation. The transgenic plants were screened and selected on Murashige and Skoog (MS) medium containing 30-50 mg l(-1) kanamycin and verified by polymerase chain reaction (PCR) and Southern blotting. Expression of the gene led to synthesis and accumulation of mannitol in the transgenic plants. Gas chromatography and mass spectrometry (GC/MS) and capillary gas chromatography (GC) showed that transgenic plants accumulated much more mannitol in their tissues than the wild-type plants, whether cultured in vitro, or grown hydroponically or in the field. Increased salt tolerance of transgenic plants was observed both in vitro and in hydroponic culture. The transgenic buds rooted normally on MS medium containing 50 mM NaCl, whereas wild-type buds did not. In the 40-day hydroponic experiments, transgenic poplar plants survived in a 75-mM NaCl treatment, whereas the wild-type poplar plants tolerated only 25 mM NaCl. Under the same NaCl stress, stomatal conductance, transpiration rates and photosynthetic rates were all higher in transgenic plants than in wild-type plants, whereas cellular relative conductivity was lower. We demonstrated that the mtlD gene was expressed in transgenic poplar plants, resulting either directly or indirectly in mannitol accumulation and improved salt tolerance. The constant mannitol concentrations in transgenic plants during the NaCl treatments indicated that mannitol accumulation caused by the mtlD gene was not a consequence of NaCl stress. Height growth was reduced by about 50% in the transgenic plants compared with the wild-type plants in the absence of salt; however, relative growth rate was much less influenced by salt stress in transgenic plants than in wild-type plants. The stunted growth of the transgenic plants may in part explain their improved salt tolerance.     

Overexpression of the ThTPS gene enhanced salt and osmotic stress tolerance in Tamarix hispida

Trehalose is a non-reducing disaccharide with high stability and strong water absorption properties that can improve the resistance of organisms to various abi-otic stresses.Trehalose-6-phosphate synthase (TPS) plays important roles in trehalose metabolism and signaling.In this study,the full-length cDNA of ThTPS was cloned from Tamarix hispida Willd.A phylogenetic tree includ-ing ThTPS and 11 AtTPS genes from Arabidopsis indicated that the ThTPS protein had a close evolutionary relationship with AtTPS7.However,the function of AtTPS7 has not been determined.To analyze the abiotic stress tolerance function of ThTPS,the expression of ThTPS in T.hispida under salt and drought stress and JA,ABA and GA3 hormone stimu-lation was monitored by qRT-PCR.The results show that ThTPS expression was clearly induced by all five of these treatments at one or more times,and salt stress caused par-ticularly strong induction of ThTPS in the roots of T.hispida.The ThTPS gene was transiently overexpressed in T.his-pida.Both physiological indexes and staining results showed that ThTPS gene overexpression increased salt and osmotic stress tolerance in T.hispida.Overall,the ThTPS gene can respond to abiotic stresses such as salt and drought,and its overexpression can significantly improve salt and osmotic tolerance.These findings establish a foundation to better understand the responses of TPS genes to abiotic stress in plants.     

Disturbance changes arbuscular mycorrhizal fungal phenology and soil glomalin concentrations but not fungal spore composition in montane rainforests in Veracruz and Chiapas,Mexico

Mexican montane rainforests and adjacent disturbed areas were studied for disturbance-related spatio-temporal changes to the arbuscular mycorrhizal fungal (AMF) community and soil glomalin concentration. The AMF community functions to both improve plant growth and soil conditions and is thus an important component to the restoration of this forest type to disturbed areas. The study areas included mature rainforests that were converted to pine forests, milpas, pastures and shrub/herbaceous plant communities via burning and logging. Seasonal patterns in AMF spore species richness and sporulation significantly differed across disturbance types at two of the three sites surveyed. Contrasting patterns of sporulation among AMF families across different disturbance types helped to explain how species richness and composition were maintained despite dramatic changes to the host plant community. Meaning, in most cases, disturbance induced changes in when different AMF taxa sporulated but not what taxa sporulated. Only conversion from mature pine–oak–Liquidambar–Persea forests to pine-dominated stands severely reduced AMF spore richness and total sporulation. Surprisingly, in pine-dominant stands no concomitant negative impacts on soil glomalin (MAb32B11 immunoreactive soil protein) concentrations were detected. However, soils of mature forests containing no pines had the highest concentration of glomalin. Conversion to pasture and milpa (diverse cornfield) had a strong negative impact on the concentration of soil glomalin concentrations. In sharp contrast, the same disturbance types improved AMF sporulation and AMF spore richness. It appears that disturbance type, and not AMF community measures used herein, best predicts changes in soil glomalin concentration.     

Defensin (TvD1) from Tephrosia villosa exhibited strong anti-insect and anti-fungal activities in transgenic tobacco plants

Plant defensin is a small, cationic, cysteine-rich broad-spectrum antimicrobial peptide with four or five disulfide bridges and has been shown to be a component of the innate immunity system in plants. In the present study, the defensin gene (TvD1) from Tephrosia villosa was overexpressed in tobacco and characterized. Two high-expression (T1, T26) and one low-expression (T13) plant lines were selected through semi-quantitative RT-PCR and used for bioassays along with non-transgenic controls. The high-expression plant line exhibited strong in vivo anti-fungal and anti-feedant activity against the pathogen Rhizoctonia solani and the first and second instar larvae of the Spodoptera litura (F.), the tobacco cutworm, respectively. The low-expression plant line showed a moderate level of tolerance/resistance in the bioassays. The recombinant peptide (rTvD1) exhibited toxicity to tobacco pollen grains in the germination assay, but transgenic plants produced copious fertile pollen and set capsules with viable seeds. The results of this study demonstrate that the single gene (TvD1) effectively controls both fungal and insect pests and, hence, it can be used for crop transformation.     

A combination of morphological and molecular analyses to distinguish two fungal pathogens causing leaf spots on Cinnamomum burmannii

The leaves of Cinnamomum burmannii in Guangdong Province were severely affected by two distinctly different types of spots. The dark spot was round, surrounded by a thin yellow zone at the interface between healthy and affected regions, and had a distinct dark ring. The yellow spot had an irregular shape and a broad yellow halo. The pathogens from the different diseased leaves were isolated and were shown to be of two different strains, both of which caused leaf spot disease in pathogenicity tests. Based on the morphological characteristics and ITS sequence, the strain causing the dark leaf spot was identified as Phyllosticta cirsii, and that causing the yellow leaf spot as Phomopsis cinnamomicola Z.D. Jiang et al. This paper is the first to report two pathogens causing leaf spots on Cinnamomum burmannii.     

Response of fungal and plant communities to management-induced overstorey changes in montane forests of the Western Carpathians

The effect of forest management on biodiversity is a crucial issue for sustainable forestry and nature conservation. However, the ways in which management affects macrofungal and plant communities and diversity of mountain temperate forests still remain poorly understood. We performed a random sampling stratified by stand age and stand type on the sites of temperate montane fir–beech forests. Diversity of macrofungi and the vascular plant understorey in beech- and spruce-dominated managed stands was investigated and compared to primeval forests located in the Po?ana Biosphere Reserve, Western Carpathians. Both the vascular plant and the macrofungal communities were altered by management, and the response of the macrofungal species (especially wood-inhabiting fungi) was more pronounced in terms of species composition change. Species turnover evaluation seems to be an important tool of forest natural status assessment, because alpha diversity did not change as much as species composition. Certain species of Carpathian primeval forests were confirmed as good indicators for natural forest change; others were proposed. Species pool and mean number of species per plot were the highest in unmanaged fir–beech forests, and species diversity significantly decreased in spruce plantations. The number of species decreased significantly due to the change of canopy tree species composition only in the macrofungal communities. As an outcome for forest management, we recommend keeping mixed forests involving all natural tree species and providing at least a minimal amount of dead wood necessary for wood-inhabiting organisms and leaving some area of unmanaged natural forests within complexes of managed stands.     

Cloning and RNAi construction of a LEAFY homologous gene from Populus tomentosa and preliminary study in tobacco

PtLFY, a LEAFY (LFY) gene, was cloned from Populus tomentosa (LM50) by PCR. Sequencing analysis indicated that PtLFY was 2 629 bp long, composed of three exons and two introns and encoded 378 amino acids. The splice donor sites and the splice acceptor sites were in identical positions to the LFY and its homologues. The amino acid sequence inferred was 68%-99% homologous to those of LFY and its homologues by blast analysis in GenBank. The Southern blot analysis indicated that there was a single copy of the PtLFY gene in genomic DNA of male and female P. tomentosa (LM50 and 5082). The pBI121-Ptalfy (reverse)-intron-Ptlfy-GUS-nos was constructed using RNA interference (RNAi) technique and verified by PCR and digestion identification and transformed into tobacco. Some transgenic tobacco plants were obtained by PCR and PCR-Southern identification. The growth was generally repressed in transgenic tobacco plants compared with wild-type ones and some phenotypic differences were observed. [Supported by the National Natural Science Foundation of China (Grant No. 30371175) and Postdoctoral Foundation of China (Grant No. 2002032041)]     

Methyl jasmonate induces changes mimicking anatomical defenses in diverse members of the Pinaceae

Conifers have defenses such as the production of phenolic compounds and resins that can be induced by bark beetles and other invading organisms, but the signaling agents involved are unknown. The anatomical effects of methyl jasmonate (MJ), a potent inducer of certain plant defenses, were compared with wounding of the bark of 12-15-year-old trees of five conifer species. Wounding in all species resulted in tissue necrosis and wound periderm development immediately around the wound site. One cm from the wound, swelling of phloem polyphenolic parenchyma cells and phenolic accumulation were observed in Pseudotsuga menziesii (Mirb.) Franco, Picea pungens Engelman, Larix occidentalis Nutt. and Pinus monticola Douglas ex D. Don, but not in Taxus brevifolia Nutt. Traumatic resin ducts were formed in response to wounding in three species of Pinaceae, but not in P. monticola, which formed irregular clusters of cells rather than ducts. Taxus brevifolia did not form resin ducts in response to either wounding or MJ treatment. In the Pinaceae species studied, surface application of 100 mM MJ caused similar anatomical changes to those observed in response to wounding, including phenolic accumulation, cell swelling and traumatic resin duct formation, but it did not induce a wound periderm. Traumatic resin ducts differed in size among the study species, ranging from small in L. occidentalis to very large in P. menziesii. In P. menziesii, P. pungens and L. occidentalis, traumatic resin ducts were more abundant after MJ treatment than after wounding. We conclude that the octadecanoid pathway is likely involved in defense responses in stems of the Pinaceae, but not necessarily in other taxa.     

浅谈大庆市野生花卉的引种与栽培

通过对大庆地区野生花卉的引种栽培,筛选繁育出10 余种适合大庆地区城市园林绿化的野生花卉品种。并详细介绍了每个品种的栽培特性,以丰富大庆地区盐碱地绿化、彩化植物材料。     

衡阳市花木虫害调查与防治

对衡阳市花木害虫种类、危害情况、发生规律进行了多年调查,共查出危害程度较大的害虫32种,并分析了衡阳市花木虫害持续发生的原因,提出了相应的防治对策。     

野生花卉在景观设计中的选择与应用

文章在强调野生花卉植物在景观设计中具有重要应用价值的基础上,阐述其选择依据、配置原则以及应用形式,重点介绍江苏省有观赏价值的野生草本花卉的观赏特性、生态适应性和可供选择的园林用途,以期对该地区景观植物配植有一定的指导意义和参考价值。       

Over expression of TaFer gene from Tamarix androssowii improves iron and drought tolerance in transgenic Populus tomentosa

Ferritin, a universal intracellular protein, can store large amounts of iron and improve plant resistance to abiotic and biotic stress. In this study, a ferritin gene(TaFer) from Tamarix androssowii Litv. was transferred into Populus tomentosa Carr. cv 'BJR01' via Agrobacterium. Six independent transgenic lines were obtained with a tolerance to kanamycin and three were randomly selected for further analysis. The PCR and RT-PCR results indicate that the TaFer gene had been integrated into the poplar genome. The effect of the gene on abiotic stress tolerance was tested, and the results show that transgenic plants improve growth, had higher chlorophyll and lower MDA contents, and higher relative electrical conductivity,fewer changes of SOD and POD activities, higher iron content, higher root ferric reductase activity and lower levels of ROS accumulation and cell death in response to drought, Fe-insufficient or Fe-excess tolerance. These results indicate that the TaFer gene can improve abiotic stress tolerance in transgenic Populus tomentosa.     

Oxidase activity in lignifying xylem of a taxonomically diverse range of trees: identification of a conifer laccase

In a diverse taxonomic range of tree species, including representative species of ancient families of angiosperms (Magnolia x soulangiana Soul.-Bod.) and gymnosperms (Ginkgo biloba L.), oxidase activity was associated with cell walls of developing xylem and was enriched in extracts of cell wall-associated glycoproteins. In all species where oxidase activity was detected histochemically, it was expressed in cell walls of lignifying, differentiating xylem cells and was absent from old wood, cambium and phloem, suggesting that oxidases have a conservative role in lignification of tree xylem. An oxidase from the developing xylem of Picea sitchensis (Bong) Carr. (Sitka spruce) was partially purified by a combination of lectin affinity and immobilized metal ion affinity chromatography. A portion of the total oxidase activity had high affinity for immobilized zinc ions and this feature allowed it to be separated from the bulk of oxidase activity. Two polypeptides that could have been responsible for the bound oxidase activity were enriched by this procedure. The smaller polypeptide of Mr approximately 73 kDa yielded an N-terminal amino-acid sequence that was homologous to laccase-like polyphenol oxidases (E.C. 1.10.3.2) from loblolly pine (Pinus taeda L.), poplar (Populus euramericana (Dode) Guinier) and Arabidopsis. The larger polypeptide (Mr approximately 77 kDa) yielded an N-terminal amino-acid sequence that was homologous with a range of plant subtilisin-like serine proteinases. The roles of oxidase and proteinase activities in developing xylem are discussed.     

宿根花卉的特点及其在园林中的配置

根据宿根花卉种类繁多、色彩丰富、生长稳定、抗逆性强的特点,其在园林中的配置,宜于建花坛、花境,也可群植,与背景树相结合,还可作地被植物代替草坪,也可建单类花卉园.     

园林植物及其应用--现代鲜切花栽培技术及其应用

从种苗繁殖、栽培设施、栽培系统、花期调控、病虫害防治、鲜切花保鲜、长距离运输、检验检疫等方面系统地阐述了现代鲜切花的栽培技术,兼顾了先进性与实用性的统一,对生产单位有较强的指导意义.     

Molecular cloning of a cellulose synthase gene PtoCesA1 from Populus tomentosa and its genetic transformation in tobacco

A 3 125 bp cellulose synthase gene, PtoCesA1, which has a 98% identity to PtrCesA1 from Populus tremuloides, was cloned from cDNA prepared from secondary xylem of P. tomentosa. Four anti-expression vectors with different fragments of PtoCesA1, named as pBIPF, pBICC1, pBIPR and pBIBR, were constructed. Some traits of transformed tobacco of pBICC1, pBIPR and pBIBR differed from wild types, such as small leaves, “dwarf” phenotype and thinner xylem and fiber cell walls than wild plants consistent with a loss of cellulose. It indicated that the growth of transgenic tobacco was restrained by the expression of anti-PtoCesA1. Transgenic tobacco was obtained and the contents of cellulose and lignin were analyzed as well as the width and length of fiber cells, and xylem thickness for both transgenic and control plants. Transformed tobacco showed a different phenotype from control plants and it implied that PtoCesA1 was essential for the cellulose biosynthesis in poplar stems. [Supported by the Hi-Tech Research and Development Program of China (863) (2001AA244060 and 2003AA244020) and National Basic Research Program of China (973) (J1999016003)]