甾醇生物合成抑制剂粉锈宁对苹果黑星病菌发育的影响

采用电子显微镜和细胞化学技术,研究了杀菌剂粉锈宁（甾醇生物合成抑制剂）对苹果黑星病菌在苹果叶片上发育的影响。观察结果表明,接种前24h施药对病菌入侵有明显的影响。表现为分生孢子的萌发受阻,推迟萌发及萌发率降低;并引起芽管畸形,不能形成附着胞。接种后6天（显症前）施药,可引起叶片角质层下菌丝细胞和子座细胞的原生质坏死、细胞壁不规则增厚及液泡增大, 从而使菌丝进一步发育受阻。接种后12天（显症后）施药,不仅导致菌丝、子座细胞发生上述变化, 而且引起分生孢子和分生孢子梗塌陷、畸形,阻止了病菌的进一步产孢和扩展。细胞化学定位分析结果表明,?-1,3-葡聚糖和几丁质这两种胞壁主要成分在对照菌丝和药剂处理后的菌丝细胞壁内含量有很大差异。在药剂处理的菌丝细胞壁中,这两种成分的标记密度明显高于对照菌丝,表明杀菌剂对病菌质膜透性的不利影响使?-1,3-葡聚糖和几丁质在菌丝细胞壁中过度累积。     

三唑酮对玉米弯孢病菌超微结构和细胞化学的影响

三唑酮(triadimenfon)属于麦角甾醇类生物合成抑制剂(ergosterol biosynthesis inhibitors．EBI),具有较广的抗真菌谱,明确其对玉米弯孢菌发育的影响可为该杀菌剂的田间应用提供理论依据。利用电镜技术和细胞化学技术观察的结果表明,玉米率孢菌经三唑酮处理后,菌丝生长明显受到抑制,表现为菌落生长速度减慢、菌丝分枝增多,且不观则地肿大和缢缩,出现许多瘤状突起,处理菌丝明显畸形。透射电镜观察结果表明,三唑酮可引起菌丝细胞壁不规则增厚,特别是菌丝顶端细胞壁增厚尤为明显:菌丝细胞隔膜发育受阴而表现畸形;菌丝细胞外有大量电子染色深的外渗物质。细胞化学标记定位结果表明,真菌细胞壁主要成分β-1,3-葡聚糖和几丁质的含量在药剂处理后发生很大变化,其标记密度明显低于未处理的对照菌丝,表明病菌细胞壁的结构和功能受到明显的不利影响。论文对弯孢菌受三唑酮影响后胞壁成份变化与其它真菌不同的原因进行了讨论。     

甾醇生物合成抑制剂粉锈宁对苹果黑星病发育的影响

采用电子显微镜和细胞化学技术,研究了杀菌剂粉锈宁（甾醇生物合成抑制剂）对苹果黑星病菌在苹果叶片上发育的影响。观察结果表明,接种前24h施药对病菌入侵有明显的影响。表现为分生孢子的萌发受阻,推迟萌发及萌发率降低。并引起芽管畸形,不能形成附着胞。接种后6天（显症前）施药,可引起叶片角质层下菌丝细胞和子座细胞的原生质坏死、细胞壁不规则增厚及液泡增大,从而使菌丝进一步发育受阻。接种后12天（显症后）施药,不仅导致菌丝、子座细胞发生上述变化,而且引起分生孢子和分生孢子梗塌陷、畸形,阻止了病菌的进一步产孢和扩展。细胞化学定位分析结果表明,β－1,3－葡萄糖和几丁质这两种胞壁主要成分在对照菌丝和药剂处理后的菌丝细胞壁内含量有很大差异。在药剂处理的菌丝细胞壁中,这两种成分的标记密度明显高于对照菌丝,表明杀菌剂对病质膜透性的不利影响使β－1,3－葡聚糖和几丁质在菌丝细胞壁中过度累积。     

戊唑醇对小麦纹枯菌超微结构的影响

用光镜和电镜技术研究了新型三唑类杀菌剂戊唑醇对小麦纹枯病菌发育的组织学和超微结构的影响.光镜和电镜观察发现戊唑醇处理导致病菌发生一系列变化菌丝呈现念珠状异常膨大和缢缩,菌丝原生质体内液泡和电子致密体增多,菌丝细胞壁不规则加厚,部分菌丝的隔膜发育受阻成畸形,不能形成正常的桶孔隔膜和桶孔覆垫.有些菌丝原生质体内出现菌丝内套菌丝的现象.这些变化最终导致菌丝细胞解体死亡.     

戊唑醇对小麦纹枯菌超微结构的影响*

用光镜和电镜技术研究了新型三唑类杀菌剂戊唑醇对小麦纹枯病菌发育的组织学和超微结构的影响。光镜和电镜观察发现戊唑醇处理导致病菌发生一系列变化：菌丝呈现念珠状异常膨大和缢缩,菌丝原生质体内液泡和电子致密体增多,菌丝细胞壁不规则加厚,部分菌丝的隔膜发育受阻成畸形,不能形成正常的桶孔隔膜和桶孔覆垫。有些菌丝原生质体内出现菌丝内套菌丝的现象。这些变化最终导致菌丝细胞解体死亡。     

戊唑醇对小麦纹枯菌超微结构的影响

用光镜和电镜技术研究了新型三唑类杀菌剂戊唑醇对小麦纹枯病菌发育的组织学和超微结构的影响,光镜和电镜观察发现戊唑醇处理导致病菌发生一系列变化：菌丝呈现念珠状异常膨大和缢缩,菌丝原生质体内液泡和电子致密体增多,菌丝细胞壁不规则加厚,部分菌丝的隔膜发育受阻成畸形,不能形成正常的桶孔隔膜和桶孔覆垫。有些菌丝原生质体内出现菌丝内套菌丝的现象,这些变化最终导致菌丝细胞解体死亡。     

水杨酸和黄萎病菌毒素处理棉花愈伤组织使β-1,3-葡聚糖酶和几丁质酶的活性增加

不同品种棉花(Gossypium hirsutum L.)愈伤组织对黄萎病菌毒素粗提物的抗性与体内β-1,3-葡聚糖酶和几丁质酶活性水平有关.在毒素处理下,抗性品种比感性品种酶活性增加的幅度大、时间早.外源水杨酸(SA)处理后,棉花愈伤组织中的β-1,3-葡聚糖酶和几丁质酶活性增加.抗β-1,3-葡聚糖酶多克隆抗体与28 kD的蛋白条带有免疫交叉反应,毒素、SA、毒素+SA均能诱导该蛋白条带出现.     

寡糖对向日葵叶片细胞病程相关蛋白及细胞壁物质的诱导作用

用寡糖对向日葵叶片进行喷雾,研究了该寡糖对向日葵叶片细胞内几丁质酶和β-1,3-葡聚糖酶2种病程相关蛋白(PRs蛋白)以及木质素、富含羟脯氨酸蛋白(HRGP)2种细胞壁物质含量的影响.结果表明,经寡糖处理后,向日葵叶片中β-1,3-葡聚糖酶和几丁质酶的活性均升高,最高值分别比同期CK增加36.38%和6.35%;木质素及HRGP含量也诱导增加,最高值分别比同期CK显著增加39.15%和47.13%.在寡糖处理后接种病原菌的向日葵叶片中,β-1,3-葡聚糖酶及细胞壁物质被诱导合成,且合成量均较单独寡糖处理与单独接种锈菌处理要高.研究发现,诱导向日葵幼苗叶片的几丁质酶、β-1,3-葡聚糖酶活性增强和细胞壁木质素、HRGP含量增加,可能是寡糖预处理增强向日葵抗锈性的内在机制.     

水杨酸和黄萎病菌毒素处理棉花愈伤组织使β-1，3-葡聚糖酶和几丁质酶的活性增加

不同品种棉花(Gossypium hirsutum L．)愈伤组织对黄萎病菌毒素粗提物的抗性与体内β-l,3-葡聚糖酶和几丁质酶活性水平有关。在毒素处理下,抗性品种比感性品种酶活性增加的幅度大、时间早。外源水杨酸(SA)处理后,棉花愈伤组织中的β-1,3-葡聚糖酶和几丁质酶活性增加。抗β-1,3-葡聚糖酶多克隆抗体与28 kD的蛋白条带有免疫交叉反应,毒素、SA、毒素 SA均能诱导该蛋白条带出现。     

甲霜灵对大豆疫霉野生菌株及突变菌株生长发育影响的细胞学研究

本文利用电子显微镜技术研究了内吸性杀菌剂甲霜灵(Metalaxyl)对大豆疫霉Phytophthoras ojae野生菌株和突变菌株的形态学及超微结构的影响。结果表明:不同浓度甲霜灵处理后可导致野生菌株和突变菌株发生一系列不同的变化。低浓度(1μg/mL)处理后,野生菌株在培养基上的生长即可受到抑制,菌丝呈现不规则的肿胀、过度分枝;菌丝细胞壁不规则加厚,菌丝细胞内液泡增加,脂肪粒累积,细胞器排列紊乱,原生质最终坏死。随浓度的升高,野生菌株立即停止生长,菌丝干瘪坏死。而突变菌株只在高浓度(10μg/mL)甲霜灵处理后顶端菌丝出现少量较小的分枝,菌丝细胞壁无增厚现象,但细胞内脂肪粒大量积累,明显高于敏感性菌株;突变菌株在高浓度甲霜灵压力下仍继续生长。     

内吸杀菌剂甲霜灵对向日葵霜霉菌发育的影响

利用电镜技术研究了内吸杀菌剂甲霜灵对向日葵霜霉菌在寄主向日葵上发育的影响。观察发现甲霜灵引起病菌发生一系列的变化。病菌胞间菌丝细胞内液泡、电子致密体增加,线粒体肿胀畸形;菌丝细胞壁不规则地加厚,部分极度加厚的细胞壁构成了假隔膜,并且在菌丝上还有不规则的突起形成。病菌吸器外间质明显不规则地变宽,其中充满大量电子致密度高的物质：部分吸器体不能正常扩张膨大,发育受阻而成畸形。向日葵霜霉菌的以上变化导致菌丝细胞和吸器的坏死,从而抑制了病菌的进一步发育。     

种衣剂17号包衣对小麦条锈菌发育影响的超微结构研究

本研究采用电镜技术研究了种衣剂17号对小麦条锈菌发育的影响。观察结果表明,该种衣剂引起病菌和寄主细胞内发生了一系列变化。病菌菌丝和吸器内脂肪粒和液泡明显增加;菌丝壁和吸器壁呈不规则加厚;菌丝分枝处无隔膜产生或隔膜畸形;有的吸器母细胞产生的畸形入侵栓,大都不能穿透寄主细胞壁,初生吸器外间质内沉积有染色较深的物质,次生吸器可产生多个不规则分枝,但不能扩张膨大;菌丝外渗的物质可能引起寄主细胞的坏死;大多数受侵寄主细胞可分泌形成较大的胼胝质,有时寄主细胞分泌的物质可将吸器体完全包围起来。上述结果表明,种衣剂17号不仅可直接作用于条锈菌,而且也可通过影响寄主而间接地影响病菌。     

An IQGAP-related protein,encoded by AgCYK1, is required for septation in the filamentous fungus Ashbya gossypii

In filamentous ascomycetes hyphae are compartmentalized by septation in which the cytoplasm of the compartments are interconnected via septal pores. Thus, septation in filamentous fungi is different from cytokinesis in yeast like fungi. We have identified an Ashbya gossypii orthologue of the Saccharomyces cerevisiae CYK1 gene which belongs to the IQGAP-protein family. In contrast to S. cerevisiae disruption of AgCYK1 yields viable mutant strains that exhibit wildtype-like polarized hyphal growth rates. In the Agcyk1 mutant cortical actin patches localize to growing hyphal tips like wildtype, however, mutant hyphae are totally devoid of actin rings at presumptive septal sites. Septation in wildtype results in the formation of chitin rings. Agcyk1 mutant hyphae are aseptate and do not accumulate chitin in their cell walls. Agcyk1 mutant strains are completely asporogenous indicating that septation is essential for the formation of sporangia in A. gossypii. AgCyk1p-GFP localizes to sites of future septation as a ring prior to chitin depositioning. Furthermore, decrease in Cyk1p-ring diameter was found to be a prerequisite for the accumulation of chitin and septum formation.     

柿树炭疽菌侵染寄主的细胞学研究*

超微结构研究表明,柿树炭疽菌(Colletotrichum gloeosporioides)侵染后在寄主细胞中形成初生菌丝和次生菌丝,寄主细胞膜外沉积了一层厚的电子不透明物质,初生菌丝与具有沉积物的寄主原生质膜之间有一层界面基质(interfacial matrix)。当初生菌丝扩张并侵染相邻细胞时, 围绕着初生菌丝层的界面基质消失,具有沉积物的原生质膜被逐步降解。初生菌丝在穿透寄主细胞壁过程中形成一个漏斗状的菌丝锥,然后穿透寄主细胞壁并迅速膨大, 然后形成厚壁的初生菌丝。初生菌丝在寄主细胞壁中收缩狭窄处产生一个隔膜,隔膜两边菌丝中细胞质的电子密度明显不同,菌丝锥中有浓密的电子密度。死体营养的次生菌丝在死的细胞中繁殖和扩展,并产生分枝。次生菌丝可直接穿透较薄的寄主细胞壁,无缢缩或任何变形现象,菌丝顶端部分未见隔膜产生;在穿透较厚的细胞壁时,靠近顶端处产生隔膜,顶端细胞膨大,使寄主细胞壁撕裂。接种90h后分生孢子盘在枝条表面形成。柿树炭疽菌其侵染过程有两个阶段,即初生菌丝的活体营养阶段和次生菌丝的死体营养阶段。     

Vacuole inheritance regulates cell size and branching frequency of Candida albicans hyphae

Hyphal growth of Candida albicans is characterized by asymmetric cell divisions in which the subapical mother cell inherits most of the vacuolar space and becomes cell cycle arrested in G1, while the apical daughter cell acquires most of the cell cytoplasm and progresses through G1 into the next mitotic cell cycle. Consequently, branch formation in hyphal compartments is delayed until sufficient cytoplasm is synthesized to execute the G1 'START' function. To test the hypothesis that this mode of vacuole inheritance determines cell cycle progression and therefore the branching of hyphae, eight tetracycline-regulated conditional mutants were constructed that were affected at different stages of the vacuole inheritance pathway. Under repressing conditions, vac7 , vac8 and fab1 mutants generated mycelial compartments with more symmetrically distributed vacuoles and increased branching frequencies. Repression of VAC1 , VAM2 and VAM3 resulted in sparsely branched hyphae, with large vacuoles and enlarged hyphal compartments. Therefore, during hyphal growth of C. albicans the cell cycle, growth and branch formation can be uncoupled, resulting in the investment of cytoplasm to support hyphal extension at the expense of hyphal branching.     

Antifungal activity of rye (Secale cereale) seed chitinases: the different binding manner of class I and class II chitinases to the fungal cell walls

The antifungal activities of rye seed chitinase-a (RSC-a, class I) and -c (RSC-c, class II) were studied in detail using two different bioassays with Trichoderma sp. as well as binding and degradation experiments with the cell walls prepared from its mycelia. RSC-a inhibited more strongly the re-extension of the hyphae, containing mainly mature cells, than RSC-c did. Upon incubation of the fungus with fluorescent chitinases, FITC-labeled RSC-a was found to be located in the hyphal tips, lateral walls, and septa, while FITC-labeled RSC-c was only in the hyphal tip. RSC-a had a greater affinity for the cell walls than RSC-c. RSC-a liberated a larger amount of reducing sugar from the cell walls than RSC-c did. These results inferred that RSC-a first binds to the lateral walls and septa, consisting of the mature cell walls, and degrades mature chitin fiber, while RSC-c binds only to the hyphal tip followed by degradation of only nascent chitin. As a result, RSC-a inhibited fungal growth more effectively than RSC-c. Furthermore, it was suggested that the chitin-binding domain in RSC-a assists the antifungal action of RSC-a by binding to the fungal hypha.