Sinorhizobium meliloti succinylated high‐molecular‐weight succinoglycan and the Medicago truncatula LysM receptor‐like kinase MtLYK10 participate independently in symbiotic infection

The formation of nitrogen‐fixing nodules on legume hosts is a finely tuned process involving many components of both symbiotic partners. Production of the exopolysaccharide succinoglycan by the nitrogen‐fixing bacterium Sinorhizobium meliloti 1021 is needed for an effective symbiosis with Medicago spp., and the succinyl modification to this polysaccharide is critical. However, it is not known when succinoglycan intervenes in the symbiotic process, and it is not known whether the plant lysin‐motif receptor‐like kinase MtLYK10 intervenes in recognition of succinoglycan, as might be inferred from work on the Lotus japonicus MtLYK10 ortholog, LjEPR3. We studied the symbiotic infection phenotypes of S. meliloti mutants deficient in succinoglycan production or producing modified succinoglycan, in wild‐type Medicago truncatula plants and in Mtlyk10 mutant plants. On wild‐type plants, S. meliloti strains producing no succinoglycan or only unsuccinylated succinoglycan still induced nodule primordia and epidermal infections, but further progression of the symbiotic process was blocked. These S. meliloti mutants induced a more severe infection phenotype on Mtlyk10 mutant plants. Nodulation by succinoglycan‐defective strains was achieved by in trans rescue with a Nod factor‐deficient S. meliloti mutant. While the Nod factor‐deficient strain was always more abundant inside nodules, the succinoglycan‐deficient strain was more efficient than the strain producing only unsuccinylated succinoglycan. Together, these data show that succinylated succinoglycan is essential for infection thread formation in M. truncatula, and that MtLYK10 plays an important, but different role in this symbiotic process. These data also suggest that succinoglycan is more important than Nod factors for bacterial survival inside nodules.     

Evaluation of an indigenous ELISA for diagnosis of Johne’s disease and its comparison with commercial kits

Country lacks sensitive and indigenous diagnostic kits for the screening of goats and sheep against Johne’s disease. Therefore an indigenous ELISA kit was developed using protoplasmic antigen from native Mycobacterium avium subspecies paratuberculosis ‘Bison Type’ strain of goat origin (Kit 1). In the present study, kit 1 and two commercial kits (kit 2 and 3) were evaluated with respect to ‘Gold Standard’ fecal culture in 71 animals (55 goats and 16 sheep). Kit 1 using indigenous antigen (protoplasmic antigen) was sensitive at very low concentration (0.1 μgm / well) as compared to purified commercial protoplasmic antigen (4 μgm / well) used in kit 2, in the Type 1 reactors (strong positive as positive). Screening of 71 animals by fecal culture detected 38.0% animals (goats-40.0%, sheep-31.2%) as positive (clinical shedders of bacilli) from these farm animals. Of the farm animals located at Central Institute for Research on Goats, herds of goat were endemic whereas, sheep flocks were comparatively resistant to Johne’s disease. The 29.5 and 61.9, 15.4 and 57.7 and 4.2 and 14.0% animals (goats and sheep) were in the category of sero-reactors type 1 and 2 of the ELISA kits 1, 2 and 3, respectively. In the type 1 sero-reactors, sensitivity and specificity of kit 1, 2 and 3 was 53.7 and 86.0, 17.8 and 86.0 and 3.5 and 94.7%, respectively. Indigenous ELISA test (kit 1) was significantly superior for the screening of goatherds and sheep flocks against JD as compared to commercial ELISA kits (Kit 2 and 3). In comparison to kit 2 and 3, kit 1 had highest sensitivity, comparable specificity and substantial to nearly perfect proportional agreement (Kappa Scores) with respect to ‘Gold standard’ fecal culture in goats and sheep. Disease being endemic in herds and flocks screened using ELISA kits, Type I sero-rectors had better correlation with fecal culture in comparison to Type II sero-reactors therefore, used for estimation of sero-prevalence. Newly developed Indigenous ELISA kit was simple, inexpensive, sensitive and reliable for screening of goats and sheep population against Johne’s disease. The study reports high prevalence of Johne’s disease in farm goatherds and sheep flocks, using sensitive tests (fecal culture and ELISA kit). Results of Type 1 reaction in kit 1 were optimally correlated with culture and were good for estimating the sero-prevalence. For controlling Johne’s disease in endemic herds initial removal of the animals in strong positive category (Tyep 1 reactors), may help to remove heavy shedders.     

红豆草根瘤侵入线的超微结构研究

用透射电镜对红豆草根瘤侵入线的超微结构进行了观察研究.结果表明,(1)红豆草根瘤侵入线由胞间隙和胞间层细胞壁内陷形成,它们的体积较小,多为管状,基质丰富,含菌很少,常有分叉和1个以上的基质区,而且不同基质区的电子密度、细菌数量和侵入线壁厚度都不相同.(2)红豆草根瘤的侵入线十分丰富,它们不仅大量存在于根瘤分生细胞和幼龄侵染细胞中,也经常出现在发育成熟的侵染细胞内.(3)红豆草根瘤中有一种近似圆形的特殊结构,表面由一层膜包围,其内电子密度较低且无固定结构,且只位于侵染细胞的细胞质中,常在侵入线附近,从不出现在侵染细胞的液泡内和非侵染细胞里面.     

Congruent species delimitation of two controversial gold‐thread nanmu tree species based on morphological and restriction site‐associated DNA sequencing data

Species delimitation is fundamental to conservation and sustainable use of economically important forest tree species. However, the delimitation of two highly valued gold‐thread nanmu species (Phoebe bournei (Hemsl.) Yang and P. zhennan S. K. Lee & F. N. Wei) has been confusing and debated. To address this problem, we integrated morphology and restriction site‐associated DNA sequencing (RAD‐seq) to define their species boundaries. We obtained consistent results from the two datasets, supporting two distinct lineages corresponding to P. bournei and P. zhennan. In P. bournei, higher order leaf venation is more prominent, petioles are thicker, and leaf apex angle is narrower, compared to P. zhennan. Both datasets also revealed that the former putative P. bournei populations from northeastern Guizhou belong to P. zhennan. The two species are now distinct in distributions except in the Wuling Mountains, where they overlap. Phoebe bournei occurs mainly in central Fujian, southern Jiangxi, the Nanling Mountains, and the Wuling Mountains, whereas P. zhennan is found in the adjoining eastern regions of the Qionglai Mountains, the southern Sichuan hills, and the Wuling Mountains. The re‐delimitation of P. bournei and P. zhennan and clarification of their ranges provide a better scientific basis guiding the conservation and sustainable utilization of these tree species.     

Centerpiece微型钛板固定与传统丝线悬吊在颈椎后路单开门椎管扩大成形术中的应用效果比较研究

目的:比较Centerpiece微型钛板固定与传统丝线悬吊在颈椎后路单开门椎管扩大成形术中的应用效果。方法:选取于2015年2月～2017年9月期间北京大学第一医院收治的拟行颈椎后路单开门椎管扩大成形术的脊髓型颈椎病患者169例,根据治疗方式的不同将患者分为悬吊组(n=87,给予传统丝线悬吊治疗)和钛板组(n=82,给予Centerpiece微型钛板固定治疗),比较两组手术时间、术中出血量、术后颈椎疼痛时间、术后再关门发生率、轴性症状评分、日本骨科协会量表(JOA)评分、颈椎活动度、颈椎管矢状径、颈椎管横截面积、颈椎曲度、开门角度。结果:两组患者手术时间、术中出血量比较差异无统计学意义(P0.05),钛板组术后颈椎疼痛时间明显短于悬吊组,术后再关门发生率低于悬吊组(P0.05)。两组患者术后2个月、末次随访JOA评分均高于术前,且钛板组高于悬吊组(P0.05),两组患者末次随访轴性症状评分高于术后2个月,且钛板组术后2个月、末次随访轴性症状评分均高于悬吊组(P0.05)。与悬吊组相比,钛板组术后2个月、末次随访颈椎活动度、颈椎管矢状径升高(P0.05);而钛板组术后2个月颈椎管横截面积小于悬吊组,末次随访颈椎管横截面积大于悬吊组(P0.05)。悬吊组末次随访颈椎曲度小于术前、术后2个月(P0.05),钛板组手术前后颈椎曲度比较差异无统计学意义(P0.05);钛板组术后2个月、末次随访颈椎曲度、开门角度均大于悬吊组(P0.05)。结论:颈椎后路单开门椎管扩大成形术中应用Centerpiece微型钛板固定比传统丝线悬吊治疗的临床效果更好,可有效维持患者颈椎功能及活动度,并能改善神经功能。     

Localization of acid phosphatase activity in the apoplast of pea (Pisum sativum L.) root nodules grown under phosphorus deficiency

ACPase activity was localized in the apoplast of pea root nodules under phosphorus deficiency. Pea plants (Pisum sativum L. cv. Sze ciotygodniowy) where inoculated with Rhizobium leguminosarum bv. viciae 248 and were cultured on nitrogen-free medium with phosphate (−N/+P) or phosphate-deficient (−N/−P) one. In comparison with control nodules, P-deficient nodules showed the increase of ACPase activity in plant cell walls and the infection threads. The increase in bacterial ACPase activity under P-deficiency may reflect higher demand for inorganic phosphorus that is necessary for bacteria multiplication within the infection threads. The increase of ACPase activity in nodule apoplast under P stress may enlarge the availability of phosphate for plant and bacteria.     

Telemetric tracking of scatterhoarding and seed fate in a Central African forest

In seed predation studies, removal of a seed is only the first step of a dynamic process that may result in dispersal rather than seed death. This process, termed seed fate, has received little attention in African forests, particularly in Central Africa. We experimentally assessed the initial steps of seed fate for two tree species—the large‐seeded Pentaclethra macrophylla and the relatively small‐seeded Gambeya lacourtiana—in northeastern Gabon. Specifically, we evaluated whether seed size and seed consumer identity are important determinants of seed fate. We established experimental stations under conspecific fruiting trees, each comprising three seeds fitted with telemetric thread tags to facilitate their recovery, and a motion‐sensitive camera to identify visiting mammals. In total, animals removed 76 tagged seeds from experimental stations. Small Murid rats and mice primarily removed small Gambeya seeds, whereas large‐bodied rodents and mandrills primarily removed large Pentaclethra seeds. Gambeya seeds were carried shorter distances than Pentaclethra seeds and were less likely to be cached. The two large‐bodied rodents handled seeds differently: Cricetomys emini larderhoarded nearly all (N = 15 of 16) encountered Pentaclethra seeds deep in burrows, while Atherurus africanus cached all (N = 5 of 5) encountered Pentaclethra seeds singly under 1–3 cm of leaf litter and soil, at an average distance of 24.2 m and a maximum distance of 46.3 m from experimental stations. This study supports the hypothesis that seed fate varies based on seed size and seed consumer identity, and represents the first telemetric experimental evidence of larderhoarding and scatterhoarding in the region.     

Does peripheral dislodgement contribute to heterozygote deficiencies in blue mussels?

Differential loss of heterozygous individuals that move to the periphery of mussel aggregations, where they are at greater risk for dislodgement, has been proposed as an explanation for observed heterozygote deficiencies in blue mussels. To test the dislodgement hypothesis, correlations between heterozygosity and mussel motility, as well as characteristics of byssogenesis and byssal thread attachment strengths, were determined in a wild and a farmed population of blue mussels (Mytilus edulis) from New Hampshire, USA. Although both populations exhibited a heterozygote deficit as measured by three microsatellite loci, no relationship was found between heterozygosity and increased motility in either population. Similarly, no relationship was found between heterozygosity and byssogenesis or attachment strength. Hence, differential dislodgement is highly unlikely as a possible contributor to the loss of heterozygous individuals.     

黄连-姜黄水煎剂治疗豚鼠皮肤真菌感染

目的 建立石膏样毛癣菌感染皮损豚鼠动物模型并观察黄连-姜黄复方水煎剂的疗效.方法 于32只豚鼠背部建立石膏样毛癣菌感染皮损128处,分四组:(A)100%浓度复方水煎剂治疗组;(B)200%浓度复方水煎剂治疗组;(C)2%硝酸咪康唑软膏治疗组;(D)空白对照组.于感染第4天开始用药,分别于用药第0、3、7、10天做真菌镜检、培养并测量皮损直径.结果 A、B、C组治疗效果均明显好于D组(P<0.01),2%硝酸咪康唑软膏及复方水煎剂均对皮肤石膏样毛癣菌有治疗作用;B、C组治疗效果明显好于A组(P<0.01);B组治疗效果好于C组(P<0.05),治疗过程中无一例出现皮肤刺激症状.结论 黄连一姜黄复方水煎剂对皮肤石膏样毛癣菌有明显治疗作用,无刺激性,具有临床应用前景.     

Calcium localization pattern in clover root hair cells associated with infection process: Studies with aureomycin

Summary Localized regions of calcium were shown to change in clover root hair cells after infection withRhizobium trifolii as shown with the Ca⁺⁺ binding antibiotic, chlorotetracycline. Some root hairs from the immature zone showed increased calcium fluorescence distributed through most of the cell. These root hair had a morphology with a notched side wall, typical of cells infected by bacteria. The maturing root hairs that show a growing infection thread or start of an infection thread, have a similar increased calcium fluorescence, especially around the area of origin of infection thread and tip of the root hair cell.Kettering contribution no. 722.