VA菌根共生的分子生物学

VA菌根共生是植物与真菌彼此相互作用、长期演化的结果。近几年来 ,科学家们运用现代生物技术 ,试图通过 VA菌根形成中的各类特异分子事件 ,包括植物的防卫反应、菌根与根瘤共生的异同以及 P、N转运基因等 ,揭示其共生的遗传与分子机制     

Reciprocal rewards stabilize cooperation in the mycorrhizal symbiosis

Plants and their arbuscular mycorrhizal fungal symbionts interact in complex underground networks involving multiple partners. This increases the potential for exploitation and defection by individuals, raising the question of how partners maintain a fair, two-way transfer of resources. We manipulated cooperation in plants and fungal partners to show that plants can detect, discriminate, and reward the best fungal partners with more carbohydrates. In turn, their fungal partners enforce cooperation by increasing nutrient transfer only to those roots providing more carbohydrates. On the basis of these observations we conclude that, unlike many other mutualisms, the symbiont cannot be "enslaved." Rather, the mutualism is evolutionarily stable because control is bidirectional, and partners offering the best rate of exchange are rewarded.     

Lyso-phosphatidylcholine is a signal in the arbuscular mycorrhizal symbiosis

The arbuscular mycorrhizal (AM) symbiosis represents the most widely distributed mutualistic root symbiosis. We report that root extracts of mycorrhizal plants contain a lipophilic signal capable of inducing the phosphate transporter genes StPT3 and StPT4 of potato (Solanum tuberosum L.), genes that are specifically induced in roots colonized by AM fungi. The same signal caused rapid extracellular alkalinization in suspension-cultured tomato (Solanum lycopersicum L.) cells and induction of the mycorrhiza-specific phosphate transporter gene LePT4 in these cells. The active principle was characterized as the lysolipid lyso-phosphatidylcholine (LPC) via a combination of gene expression studies, alkalinization assays in cell cultures, and chromatographic and mass spectrometric analyses. Our results highlight the importance of lysophospholipids as signals in plants and in particular in the AM symbiosis.     

大豆与丛枝菌根真菌共生建立及菌根检测方法的探究

利用盆栽培养的方法,研究4种培养基质(蛭石、蛭石-土、沙-蛭石、沙-土)对不同品种大豆与AM真菌(Rhizophagus irregularis)共生的影响,比较Parker纯黑墨水和台盼蓝2种染色剂对大豆菌根的染色效果,探究放大网格交叉法和Trouvelot五级分级法在大批量菌根共生指标检测中的应用.结果表明:蛭石-...     

双接种对大豆利用不同有机磷源的影响

以有机磷为磷源,采用盆栽试验研究了接种根瘤菌、丛枝菌根真菌(AMF)和双接种对大豆吸收磷的影响。结果表明,不同磷肥处理植株干物重分别比对照增加了9.40%、7.28%和5.84%;双接种和单接种AMF真菌,大豆单个根瘤鲜重和单个根瘤干重显著增加;双接种比单接种真菌,大豆菌根侵染率显著提高。与相应的不接种对照相比,植酸钠和卵磷脂双接种处理植株吸磷量分别比对照增加了34.96%和33.78%,表明有机磷源双接种可显著提高植株有机磷的利用能力。菌根真菌和固氮微生物双接种对促进作物生长有重要意义。     

根瘤菌和丛枝菌根真菌单双接种对不同品系大豆生长的影响

为探索丛枝菌根真菌（abuscular mycorrhiza fungi, AMF）和大豆根瘤菌单双接种效果及其与不同品系大豆的匹配性,采用蛭石混土作为基质在光照培养室（26 ℃,16 h光照/8 h暗期,相对湿度75%）进行盆栽试验,探究根瘤菌与AMF单接种和双接种对我国大部分区域种植的10种不同品系大豆生长的影响。结果显示,根瘤菌Bradyrhizobium japonicum USDA110和菌根真菌Rhizophagus irregularis均能侵染10种品系大豆植株,形成共生结构。单接种根瘤菌和菌根真菌均能显著提高大豆地上部鲜质量,其中单接种根瘤菌能使品系大豆119、851、921植株地上部鲜质量增加102%~429%,单接种菌根真菌也能使大部分品系大豆地上部鲜质量增加39%~255%。根瘤菌和菌根真菌双接种条件下,菌根真菌的侵染共生表现出共生定殖延迟的现象;菌根真菌存在时,品系大豆985、851、115根系的单个根瘤体积增大,固氮酶活性增强。因此,相同接种方式对不同品系大豆影响不同,相同品系大豆经过不同接种方式处理,长势存在差异;985、115品系大豆采用双接种方式最佳,167、509、921、187品系大豆采用单接种根瘤菌方式效果最佳,119、909、045则可采用单接种根瘤菌或菌根真菌来提升产量。     

Rho蛋白家族在丛枝菌根真菌与植物共生关系建立中的功能分析

Rho家族蛋白是一类含有GTPase结构域的高度保守蛋白的总称,它是真核生物中Ras超家族主要成员之一。通过同源比对以及RACE等技术从丛枝菌根真菌（Rhizophagus irregularis）DAOM197198中分离到了3个Rho家族小G蛋白。通过与其他真菌Rho蛋白家族成员进行系统进化分析,结果表明,所分离到的RiCDC42,RiRac1,RiRho1属于高度保守的Rho蛋白家族成员;利用实时荧光定量PCR方法对这3个基因在前共生阶段和共生阶段的表达模式进行分析,结果发现RiRho1在萌发孢子中的表达量最高,而在共生时期表达下调,RiRac1和RiCDC42基因在共生时期的表达量比共生前期高。此外,本研究还利用酵母CDC42,Rho1温度敏感性突变株,稻瘟病菌ΔMgCDC42突变株以及HIGS技术对Rhizophagus irregularis Rho蛋白家族成员进行进一步研究。结果显示,RiRho1与RiCDC42基因能够互补酵母Rho1与CDC42温度敏感型表型;对RiCDC42与RiRac1进行HIGS时,Rhizophagus irregularis 丛枝发生明显的降解;RiCDC42基因能够互补稻瘟病菌ΔMgCDC42突变体部分表型,但不同的是互补菌株不产黑色素。由此推测Rho蛋白家族成员可能在丛枝菌根真菌共生关系建立的过程中具有重要的作用。     

耐铝根瘤菌的筛选及耐性菌株特性的研究

【目的】对我国南方地区的野生大豆根瘤菌进行耐铝的筛选,以期建立一套耐铝根瘤菌筛选和鉴定体系,为南方大豆区接种高效耐铝菌株奠定基础.【方法】利用菌株活化培养法分离来自湖南各县和广州地区酸性土壤中的野生大豆根瘤菌株,通过分光光度计进行耐铝检测,研究耐性菌株的生长特性以及接种后对栽培大豆的生长和结瘤的影响.【结果和结论】菌株W20能在铝浓度为200μmol·L-1的培养基上正常生长,而其他菌株的生长则受到较大抑制.菌株W20的最适生长酸度为pH 6.0,致死酸度为pH 4.0.通过质子通量试验发现,W20的细胞膜能阻止过量的H+进入细胞.在Al3+浓度为200μmol·L-1时,华夏3号接种W20菌株后地上和地下部分生物量分别比对照增加了60.9%和14.8%;瘤数和瘤质量分别提高了66%和209%;地上和地下部分铵态氮含量分别比对照高25.7%和9.4%.     

沙冬青根瘤菌多样性研究进展

在西北荒漠地区土壤缺水少氮的环境条件下,寄主植物与根瘤菌共生关系对固沙植物沙冬青的生长发育具有重要作用.沙冬青根瘤菌的多样性及其抗性与沙冬青抗旱、抗寒和抗高温的特性有着密切的关系.随着分子生物学技术的发展,微生物多样性的研究正在不断深入,尤其是功能微生物的多样性研究得到关注.加强沙冬青根瘤菌资源多样性的研究和保护,对濒危植物沙冬青的保护和利用具有重要作用.对沙冬青的研究现状,包括沙冬青根瘤菌多样性研究现状及研究方法的进展进行简单回顾和介绍.     

Fossil mycorrhizae: a case for symbiosis

Vesicular-arbuscular mycorrhizae are significant in the physiology and ecology of extant vascular plants, and they may also have played a major role in the origin of the vascular land flora. The case for fossil vesicular-arbuscular mycorrhizae rests upon hyphae and chlamydospore-like bodies in several Paleozoic taxa, but fossil arbuscles are unknown to date. Specimens from the Triassic of Antarctica represent the first known occurrence of arbuscles in the fossil record.     

丛枝菌根真菌共生对石漠化生境白枪杆生长及光合特性的影响

  目的  探究石漠化生境丛枝菌根真菌共生对白枪杆Fraxinus malacophylla生长及光合特征的影响,为植被恢复选取优势菌种提供参考。  方法  设置摩西斗管囊霉Funneliformis mosseae+农林生物肥(MN)、幼套近明球囊霉Claroideoglomus etunicatum+农林生物肥(YN)、根内根孢囊霉Rhizophagus intraradices+农林生物肥(GN)、农林生物肥(ck)共4个处理,测定不同处理下白枪杆生长(树高、胸径、根和叶生物量、叶面积、叶片色素及叶绿素)及光合特征(净光合速率、气孔导度、胞间二氧化碳摩尔分数、蒸腾速率、水分利用效率等)的变化。  结果  ①接种丛枝菌根真菌显著促进了白枪杆的生长与叶、根生物量积累(P＜0.05)。②接种摩西斗管囊霉和根内根孢囊霉显著提高了白枪杆叶绿素a、叶绿素b、叶黄素的相对含量(P＜0.05),提升率达6%~67%。③接种丛枝菌根真菌显著提高了白枪杆的净光合速率、气孔导度、蒸腾速率与水分利用效率(P＜0.05),显著降低了胞间二氧化碳摩尔分数(P＜0.05)。④主成分分析表明:气孔导度、树高、叶黄素是提高净光合速率的主控因子,平均贡献率达45.81%,叶绿素b、生物量和总叶绿素的影响次之。  结论  丛枝菌根真菌共生主要通过促进植株生长、光合色素含量,显著提高白枪杆净光合速率,其中摩西斗管囊霉为最优菌种。图5表2参33     

高寒地区红豆草根瘤菌抗逆性研究

从甘南合作、甘南夏河桑科的红豆草(Onobrychis vicilfolia)根系中分离培养得到28个根瘤菌菌株,针对各菌株的耐盐性、耐酸碱及其泌酸碱能力进行研究,结果表明:采集于桑科的红豆草根瘤编号STD111ⅠA、STD26ⅠB、STD411ⅠB、STF11ⅡA的菌株耐盐性极强,在10%NaCl培养基上正常生长;采集于合作的红豆草根瘤菌株HND26ⅠA、HND26ⅠB、HND26Ⅱ和桑科红豆草根瘤菌株STD111ⅠA、STD26ⅠB、STD411ⅠA、STD411ⅡA耐酸性最强,能在pH4.0的培养基上正常生长;耐碱性最强的是夏河地区菌株STF11ⅢA,可以在pH12.0的培养基上正常生长.进一步试验表明,菌株HND26ⅠA、HND26ⅠB、HND26Ⅱ、STD111ⅠA和STD26ⅠB既能抗pH 4.0的酸逆境,又能抗pH11.0的碱逆境.同时研究发现,菌株耐碱性的强弱与其泌酸能力相关.     

Cleaning symbiosis provides a positive reinforcer for fish

Chaetodon auriga, a conun7won marine fish in Hawaii, can be conditioned by presentation of a moving model of a cleaner fish as a positive reinforcement on an instrumental schedule. Reinforcement is probably through tactile stimulation and might help to shape the response of fish to cleaners. Tactile stimulilation night serve as a valuable reinforcer in studies of fish learning.     

不同类型土壤中大豆与根瘤菌的匹配性研究

结合黑龙江省大豆主产区的生态环境,从而筛选出适宜当地土壤条件的大豆与根瘤菌的共生体。结果表明,处理S2V1R3和S1V2R1的产量最高,二者与处理S1V1R3间的差异达1%显著水平,为有效接种提供了一定的试验依据。     

Breeding against mycorrhizal symbiosis: Modern cotton (Gossypium hirsutum L.) varieties perform more poorly than older varieties except at very high phosphorus supply levels

Cotton (Gossypium hirsutum L.) is an important fiber cash crop, but its root traits related to phosphorus (P) acquisition, including mycorrhizal root traits, are poorly understood.  Eight cotton varieties bred in northwestern China that were released between 1950 and 2013 were grown in pots with or without one arbuscular mycorrhizal fungal (AMF) species (Funneliformis mosseae) at three P supply levels (0, 50 and 300 mg P as KH₂PO₄ kg^–1).  Eleven root traits were measured and calculated after 7 wk of growth.  The more recent accessions had smaller root diameters, acquired less P and produced less biomass, indicating an (inadvertent) varietal selection for thinner roots that provided less cortical space for AMF, which then increased the need for a high P fertilizer level.  At the two lower P levels, the mycorrhizal plants acquired more P and produced more biomass than non-mycorrhizal plants (3.2 vs. 0.9 mg P per plant; 1.8 vs. 0.9 g biomass per plant at P₀; 14.5 vs. 1.7 mg P per plant; and 4.7 vs. 1.6 g biomass per plant at P₅₀).  At the highest P level, the mycorrhizal plants acquired more P than non-mycorrhizal plants (18.8 vs. 13.4 mg per P plant), but there was no difference in biomass (6.2 vs. 6.3 g per plant).  At the intermediate P level, root diameter was significantly positively correlated with shoot biomass, P concentration and the P content of mycorrhizal plants.  The results of our study support the importance of the outsourcing model of P acquisition in the root economics space framework.  Inadvertent varietal selection in the last decades, resulting in thinner roots and a lower benefit from AMF, has led to a lower productivity of cotton varieties at moderate P supply (i.e., when mycorrhizal, the average biomass of older varieties 5.0 g per plant vs. biomass of newer varieties 4.4 g per plant), indicating the need to rethink cotton breeding efforts in order to achieve high yields without very high P input.  One feasible way to solve the problem of inadvertent varietal selection for cotton is to be aware of the trade-offs between the root do-it-yourself strategy and the outsourcing towards AMF strategy, and to consider both morphological and mycorrhizal root traits when breeding cotton varieties.     

青海胡卢巴根瘤菌形态特征的研究

从青海省大通、乐都和西宁各城区采集豆科植物胡卢巴的根瘤,经分离、纯化、镜检、回接,获得10株未知菌株.根瘤菌的形态特征研究表明:胡卢巴根瘤菌菌苔的形状大多呈丝状,颜色呈微乳白色及乳白色;菌落的形状均呈圆形,菌落表面光滑、边缘整齐,隆起形状低凸,透明度较好.液体培养的培养液浑浊、无可溶性色素及菌内分化;根瘤菌类菌体的形状多数为短杆状,少数为"V"、"Y"状,类菌体的大小随着植株的生长有所增长.     

Ancient tripartite coevolution in the attine ant-microbe symbiosis

The symbiosis between fungus-growing ants and the fungi they cultivate for food has been shaped by 50 million years of coevolution. Phylogenetic analyses indicate that this long coevolutionary history includes a third symbiont lineage: specialized microfungal parasites of the ants' fungus gardens. At ancient levels, the phylogenies of the three symbionts are perfectly congruent, revealing that the ant-microbe symbiosis is the product of tripartite coevolution between the farming ants, their cultivars, and the garden parasites. At recent phylogenetic levels, coevolution has been punctuated by occasional host-switching by the parasite, thus intensifying continuous coadaptation between symbionts in a tripartite arms race.     

AM真菌对草莓的接种效应研究

为了给草莓(Fragaria ananassa)菌根化育苗提供依据,以摩西球囊霉(Glomus mosseae)为接种剂,研究了在土壤灭菌和非灭菌条件下,AM真菌对草莓生长、果实品质、植株和土壤中氮、磷含量的影响。结果表明:接种AM真菌后,草莓叶片个数、根长、株高有明显提高,并且地上部分干重在灭菌和非灭菌条件下,分别提高了15.9%和2.77%;提早开花2~3 d,果实提前成熟4~5 d;果实的单果重和Vc含量明显提高,有机酸含量明显下降;组织中氮、磷含量均有提高;明显提高了土壤中碱解N、速效P的利用率。与对照组相比,土壤灭菌条件下,AM真菌对草莓的促生作用较非灭菌处理更明显。     

Lectins: a possible basis for specificity in the Rhizobium--legume root nodule symbiosis

Soybean lectin labeled with fluorescein isothiocyanate combined specifically with all but 3 of 25 strains of the soybean-nodulating bacterium Rhizobium japonicum. The lectin did not bind to any of 23 other strains representative of rhizobia that do not nodulate soybeans. The evidence suggests that an interaction between legume lectins and Rhizobium cells may account for the specificity expressed between rhizobia and host plant in the initiation of the nitrogen-fixing symbiosis.     

甘肃不同生态区域苜蓿根瘤菌表型多样性分析

对甘肃不同生态气候区域筛选出的促生能力好的31株分离自‘阿尔岗金’(Medicago sativa‘Alogon-quin’)和‘陇东苜蓿’(Medicago sativa‘Longdong’)2个紫花苜蓿品种的根瘤菌株,进行性状测定和聚类分析.结果表明:31株供试菌中,DL67、GL16、QA33B、QL31B、WA24和WL27菌株综合功能最强;聚类分析结果表明,31株供试菌和3株对照标准菌株均为中华根瘤菌属(Sinorhizobiumsp)根瘤菌,但GA26菌株与其它33株菌株分属不同类群.