感病植物材料电镜样品制备方法的改进

对感病植物叶片的抽气方法和树胶渗透方法进行了改进。用尼龙网将叶样置于固定液液面之下。抽气过程仅需10min即可完成,并且对植物细胞和病菌细胞无任何损伤。叶样渗透采用树胶滴加渗透代替常规的树胶梯度置换渗透。从而在切片中避免了植物体表病菌与植物体表间出现分裂的现象。

植物病原真菌效应蛋白研究进展

真菌病原菌能分泌效应蛋白,影响真菌病原菌与植物的相互作用。本文概述了真菌病原菌的生活和侵染方式,以及效应蛋白的基因进化,指出真菌病原菌正是通过对基因组的区隔化完成效应蛋白基因的进化。重点讨论活体营养型、死体营养型、半活体营养型和共生营养型效应蛋白的作用机制和植物适应性,以及效应蛋白的转运、吸收和加工机制,可为研究真菌病原菌与作物的相互作用,并为未来作物抗病改良和病害防控策略的制定提供参考。

感病植物的水份丧失

综述了感病植物水份丧失的生理现象及植物萎蔫病的萎蔫机制。认为 ,镰力菌酸 ( Fusaic acid )及番茄萎焉毒素( Lycomorsmin)是致萎的化学物质。二者均具破坏寄主细胞原生质膜的半透性 ,螯化重金属和抑制呼吸酶的生理作用。毒素的致萎机制似不在于阻碍茎部维管束的输导而在破坏了输导的动力系统和增加叶部水份丧失。

Dual function of Arabidopsis A TAF1 in abiotic and biotic stress responses

NAC family genes encode plant-specific transcription factors involved in diverse biological processes. In this study, the Arabidopsis NAC gene ATAF1 was found to be induced by drought, high-salinity, abscisic acid （ABA）, methyl jasmonate, mechanical wounding, and Botrytis cinerea infection. Significant induction of ATAF1 was found in an ABA-deficient mutant aba2 subjected to drought or high salinity, revealing an ABA-independent mechanism of expression. Arabidopsis ATAFl-overexpression lines displayed many altered phenotypes, including dwarfism and short primary roots. Furthermore, in vivo experiments indicate that ATAF1 is a bonafide regulator modulating plant responses to many abiotic stresses and necrotrophic-pathogen infection. Overexpression of ATAF1 in Arabidopsis increased plant sensitivity to ABA, salt, and oxidative stresses. Especially, ATAF1 overexpression plants, but not mutant lines, showed remarkably enhanced plant tolerance to drought. Additionally, ATAF1 overexpression enhanced plant susceptibility to the necrotrophic pathogen B. cinerea, but did not alter disease symptoms caused by avirulent or virulent strains of P. syringae pv tomato DC3000. Transgenic plants overexpressing ATAF1 were hypersensitive to oxidative stress, suggesting that reactive oxygen intermediates may be related to ATAFl-mediated signaling in response to both pathogen and abiotic stresses.

Ribosome Inactivating Proteins from Plants Inhibiting Viruses

Many plants contain ribosome inactivating proteins (RIPs) with N-glycosidase activity, which depurinate large ribosomal RNA and arrest protein synthesis. RIPs so far tested inhibit replication of mRNA as well as DNA viruses and these proteins, isolated from plants, are found to be effective against a broad range of viruses such as human immunodeficiency virus (HIV), hepatitis B virus (HBV) and herpes simplex virus (HSV). Most of the research work related to RIPs has been focused on antiviral activity against HIV; however, the exact mechanism of antiviral activity is still not clear. The mechanism of antiviral activity was thought to follow inactivation of the host cell ribosome, leading to inhibition of viral protein translation and host cell death. Enzymatic activity of RIPs is not limited to depurination of the large rRNA, in addition they can depurinate viral DNA as well as RNA. Recently, Phase I/II clinical trials have demonstrated the potential use of RIPs for treating patients with HIV disease. The aim of this review is to focus on various RIPs from plants associated with anti-HIV activity.

Agroinfection of sweet potato by vacuum infiltration of an infectious sweepovirus

Sweepovirus is an important monopartite begomovirus that infects plants of the genus Ipomoea worldwide. Development of artificial infection methods for sweepovirus using agroinoculation is a highly efficient means of studying infectivity in sweet potato. Unlike other begomoviruses, it has proven difficult to infect sweet potato plants with sweepoviruses using infectious clones. A novel sweepovirus, called Sweet potato leaf curl virus-Jiangsu(SPLCV-JS), was recently identified in China. In addition, the infectivity of the SPLCV-JS clone has been demonstrated in Nicotiana benthamiana. Here we describe the agroinfection of the sweet potato cultivar Xushu 22 with the SPLCV-JS infectious clone using vacuum infiltration. Yellowing symptoms were observed in newly emerged leaves. Molecular analysis confirmed successful inoculation by the detection of viral DNA. A synergistic effect of SPLCV-JS and the heterologous betasatellite DNA-β of Tomato yellow leaf curl China virus isolate Y10(TYLCCNV-Y10) on enhanced symptom severity and viral DNA accumulation was confirmed. The development of a routine agroinoculation system in sweet potato with SPLCV-JS using vacuum infiltration should facilitate the molecular study of sweepovirus in this host and permit the evaluation of virus resistance of sweet potato plants in breeding programs.

Spring Wheat Disease and Yield Responses to Nitrogen Fertilization and Chemical Treatments

P. tritici-repentis, B. graminb and C. sativus are important diseases of spring wheat in Estonia. Field trials were carried out during 2006 and 2008 in JiSgeva PBI. Two kinds of treatments were used： Tl consisted of four different rates of basic fertilizer： NO = NOPOK0; N1 = N60P13K23, N2 = N 100P22K39; N3 = N140P31K54 kg ha^-1. T2 treatment consisted of same rates of basic fertilizers and in addition growth regulator, fungicides and leaf fertilizers. Seeds of the varieties ＂Monsun＂ and ＂Vinjett＂ were untreated. Results of the effects of fertilizers on the infections of fungal diseases on spring wheat monoculture revealed that test years had the biggest influence on infection intensity of B. graminis （REy = 50.7-59.2） in T1 and T2 and P. tritici-repentis in T2 （REy = 31.6）, whereas infection of C. sativus was more dependent on year in Tl （R2y = 37.3）. Yield correlated highly with a fertilizer rate and year. In the treatment T2, the yield depended more on weather conditions （REy = 40.7） and in T1, the yield was more dependent on fertilization rate （REF = 60.2）. We found TI to be more economic as the optimum N rate varied from N60 to N100 kg hat and the benefit in monetary terms raised from 297ε hal （＂Monsun＂ 2007） to 9056 hal （＂Vinjett＂ 2008）. In T2, N rate 60 kg ha^-1 raised the monetary benefit from 806 ha^-1 （＂Monsun＂ 2007） to 731ε ha^-1 （＂Vinjett＂ 2008）. The highest economic profit was gained by using low rates of fertilizer for ＂Monsun＂ and the highest rates of fertilizer for ＂Vinjett＂.

Alteration in Biochemical Response in Sesamum indicum upon Different Plant-Pathogen Interactions

Sesamum, an important oil yielding crop suffers a huge loss in its yield due to attack of large number of fungal pathogens. In semi-arid regions Sesamum is mainly affected by two major plant-pathogenic fungus viz. Macrophomina phaseolina and Fusarium oxysporum. The aim of the study was to analyze the metabolic alterations in Sesamum after infection with both pathogens. This accomplished by individually by （the word estimating is not quantitative） the levels of total phenolic compounds and the activities of phenylalanine ammonia lyase （PAL） of one week old plants. The PAL showed high activity in infected plants, revealing the active phase in the synthesis of secondary metabolites in the Sesamum plant after infection. As a consequence, in infected plants the contents of polyphenols along with salicylic acid （SA） considerably exceeded when compared to control plants. This in vivo study of M. phaseolina and F. oxysporum infection reveals the differences of resistance levels in sesame against these two pathogens. These results provide important information regarding the plant-pathogen interactions and also forfor Sesamum improvement programs seeking the adaptation to diverse range of fungal attack along with adverse environmental factors.

Viral infection of tobacco plants improves performance of Bemisia tabaci but more so for an invasive than for an indigenous biotype of the whitefly

The ecological effects of plant-virus-vector interactions on invasion of alien plant viral vectors have been rarely investigated. We examined the transmission of Tomato yellow leaf cur/China virus （TYLCCNV） by the invasive Q biotype and the indigenous ZHJ2 biotype of the whitefly Bemisia tabaci, a plant viral vector, as well as the influence of TYLCCNV-infection of plants on the performance of the two whitefly biotypes. Both whitefly biotypes were able to acquire viruses from infected plants and retained them in their bodies, but were unable to transmit them to either tobacco or tomato plants. However, when the Q biotype fed on tobacco plants infected with TYLCCNV, its fecundity and longevity were increased by 7- and 1-fold, respectively, compared to those of the Q biotype fed on uninfected tobacco plants. When the ZHJ2 biotype fed on virus-infected plants, its fecundity and longevity were increased by only 2- and 0.5-fold, respectively. These data show that the Q biotype acquired higher beneficial effects from TYLCCNV-infection of tobacco plants than the ZHJ2 biotype. Thus, the Q biotype whitefly may have advantages in its invasion and displacement of the indigenous ZHJ2 biotype.

Overexpression of GhPFN2 enhances protection against Verticillium dahliae invasion in cotton

Growing evidence indicates that actin cytoskeleton is involved in plant innate immune responses, but the functional mechanism remains largely unknown. Here, we investigated the behavior of a cotton profilin gene （GhPFN2） in response to Verticillium dahliae invasion, and evaluated its contribution to plant defense against this soil-borne fungal pathogen. GhPFN2 expression was up-regulated when cotton root was inoculated with V. dahliae, and the actin architecture was reorganized in the infected root cells, with a clear increase in the density of filamentous actin and the extent of actin btmdling. Compared to the wild type, GhPFN2-overexpressing cotton plants showed enhanced protection against V. dahliae infection and the actin cytoskeleton organization in root epidermal cells was clearly altered, which phenocopied that of the wild-type （WT） root cells challenged with V. dahliae. These results provide a solid line of evidence important for defense against V. dahliae infection. showing that actin cytoskeleton reorganization involving GhPFN2 is

Immunogenicity and virus-like particle formation of rotavirus capsid proteins produced in transgenic plants

The human pathogen, group A rotavirus, is the most prevalent cause of acute infantile and pediatric gastroenteritis worldwide, especially in developing countries. There is an urgent demand for safer, more effective and cheaper vaccines against rotavirus infection. Plant-derived antigens may provide an exclusive way to produce economical subunit vaccines. Virus-like particles, constituting viral capsid proteins without viral nucleic acids, are considered a far safer candidate compared with live attenuated viral vaccines. In this study, the rotavirus capsid proteins VP2, VP6 and VP7 were co-expressed in transgenic tobacco plants, and their expression levels, formation of rotavirus-like particles (RV VLPs) and immunogenicity were extensively studied. Quantitative real-time RT-PCR and Western blot analysis revealed that the expression level of vp6 was the highest while vp7 was expressed at the lowest levels. The RV VLPs were purified from transgenic tobacco plants and analyzed by electron microscopy and Western blot. Results indicated that the plant-derived VP2, VP6 and VP7 proteins self-assembled into 2/6 or 2/6/7 RV VLPs with a diameter of 60-80 nm. When orally delivered into mice with cholera toxin as an adjuvant, the total soluble protein extracted from transgenic tobacco plants induced rotavirus-specific antibodies comparable with those of attenuated rotavirus vaccines, while VP 2/6/7 induced higher serum IgG and fecal IgA titers compared with VP 2/6.