Occurrence of prophage and historical perspectives associated with the dissemination of huanglongbing in mainland China

Huanglongbing (HLB), associated with a non-culturable bacterium ‘Candidatus Liberibacter asiaticus’ (CLas), is a highly destructive citrus disease with a long but poorly documented history in China. No effective treatment for HLB is available. The identification of new prophages in abundant CLas genomic sequence data provides new insights into both the diversity of CLas strains and HLB management. In this study, CLas populations from nine provinces were surveyed for the presence of prophage. Two major prophage typing groups (PTGs) were discovered to be associated with two different altitude regions: strains of CLas in PTG1 from high altitude regions (HAR) mainly contained prophage Type 1 only or Types 1 and 3, whereas strains of CLas in PTG2 from low altitude regions (LAR) mainly contained prophage Type 2. The discovery of these CLas population patterns provides evidence for independent origins of HLB in HAR and LAR. Guangdong province is the generally recognized domestic region of origin for HLB and is primarily responsible for the dissemination of HLB in LAR through transport of seedlings. Both Yunnan and Sichuan provinces are the probable regions of origin for HLB in HAR. PTG2 was further divided into two subgroups: PTG2-1, found in Guangdong, Fujian and Guangxi and PTG2-2, found in Jiangxi, Zhejiang and Hunan. These regions and prophage types are correlated with early and late introductions of HLB in LAR. These molecular analyses were supported by studying the history of the dissemination of HLB in historical documents.     

油桃果实顶腐形成原因分析

[目的]探讨油桃果实顶腐形成的原因。[方法]以中油5号油桃果实为试材,分别测定正常油桃与顶腐油桃果实中Ca含量;从顶腐油桃上分离纯化得到致病菌,采用CTAB法提取菌丝DNA,对其进行rDNA-ITS鉴定,利用NCBI在线Blast工具进行致病菌rDNAITS同源性比较。[结果]病果果实中Ca元素含量显著低于对照;腐烂坏死部位分离出2种不同类型菌丝,分别为弱寄生菌"黑变病"与"黑酵母菌"。[结论]油桃顶腐主要是由缺钙诱发后弱寄生菌侵染造成的。     

An additional life-history tactic of masu salmon: Migration of parr to coastal habitats

Alternative life-history tactics of masu salmon Oncorhynchus masou are well documented. Subsequent to the freshwater parr stage (age ≥ 1 + years), an anadromous form migrates to the sea after smolting, while a resident form matures without seaward migration. In addition to this typical migratory dimorphism, anecdotal reports based on field observations have indicated that some underyearling masu salmon use estuarine waters. However, no empirical evidence indicates saltwater utilisation and subsequent survival in the early parr stage. Here, we used otolith microchemistry to examine whether a portion of masu salmon parr in northern Japan enters coastal habitats. The otolith Sr:Ca ratios of most juveniles collected from six rivers had consistently low values, indicating that masu salmon parr inhabiting these rivers stay only in freshwater. In contrast, in individuals from a steep-gradient river the Sr:Ca ratios increased at about a 200-µm distance from the otolith core. These results suggest that some masu salmon parr might use brackish water or sea water temporarily. In addition, three masu salmon parr were found in another steep river where a culvert located only ten metres from the river mouth completely blocked upstream migration for spawning. The Sr:Ca ratios in these fish increased at about >200 µm from the otolith core, indicating the parr had immigrated to the non-natal river from the sea. Such flexible behaviour at an early life stage may contribute to the spatial expansion of masu salmon, and the movement could moreover help to stabilise its population dynamics.     

不同磷水平和钙磷比饲粮添加植酸酶对妊娠母猪养分表观消化率的影响

本试验旨在研究不同磷水平和钙磷比饲粮添加植酸酶对妊娠母猪养分消化率的影响。试验选择遗传背景一致、2~3胎次(预产期前28 d)、体重为(221.91±7.41)kg、预产期相近的健康"长×大"二元杂交母猪36头,按照胎次、预产期均衡原则随机分为9个组,每个组4个重复。对照组饲喂基础饲粮(钙、磷水平分别为7.26、5.81 g/kg);组2为基础饲粮添加植酸酶;组3~5保持钙水平(7.26 g/kg)不变添加植酸酶,减少无机磷添加至对照组的75%、50%、25%[钙磷比为(1.35~1.63)∶1.00];组6~9保持钙磷比不变(1.25∶1.00)添加植酸酶,减少无机磷添加至对照组的75%、50%、25%、0。结果表明:1)正常磷水平下,添加植酸酶显著提高了干物质、粗灰分、有机物和磷的表观消化率(P0.05),极显著降低了粪中磷的排泄量(P0.01),有降低铜、锌排泄量的趋势(P0.10)。与对照相比,低磷水平添加植酸酶极显著提高了干物质、粗灰分、有机物、磷、钙、铁、铜、锌的表观消化率(P0.01),显著降低了粪中磷、钙、铁、铜、锌的排泄量(P0.05)。2)饲粮在保持钙水平不变或钙磷比不变的条件下添加植酸酶,随磷添加量的降低,干物质、粗灰分、有机物、磷、铁、铜、锌的表观消化率均呈线性或二次升高(P0.05),粪中磷、铁、铜、锌的排泄量呈线性或二次降低(P0.01),保持钙磷比不变,钙、粗蛋白质的表观消化率显著提高(P0.05)。3)以表观可消化磷为标准,饲粮保持钙水平不变和钙磷比不变添加植酸酶可分别替代0.91、1.27 g/kg的无机磷,减少24.70%、34.48%的粪磷排泄量。4)钙磷比不变(1.25∶1.00)组饲粮的养分表观消化率极显著高于钙水平不变[高钙磷比(1.35~1.63)∶1.00]组饲粮(P0.01),且粪矿物质的排泄量极显著减少(P0.01)。综上所述:1)在本研究条件下,在低无机磷、低钙磷比(1.25∶1.00)饲粮中,添加植酸酶提高养分消化率的效果更显著。2)以表观可消化磷为标准,母猪饲粮的钙磷比为1.25∶1.00时,添加植酸酶可减少1.27 g/kg的磷添加。     

盐胁迫下外源Ca~(2+)对红豆草幼苗抗性生理的影响

以蒙农红豆草为材料,研究了100mmol/L NaCl胁迫下不同浓度外源Ca2+对红豆草幼苗的生长、脯氨酸、可溶性糖和叶绿素含量及根系活力的影响;探讨了Ca2+对盐胁迫伤害的缓解作用。结果表明:随着Ca2+浓度的增加,与CK相比,红豆草脯氨酸、可溶性糖、叶绿素含量及根系活力呈先升高后降低的明显变化趋势,在T3(100mmol/L NaCl+30mmol/L CaCl2)处理下,红豆草脯氨酸、可溶性糖及叶绿素含量与对照相比提高了32.3%,60.0%和9.7%,差异显著(P0.05);T3、T4处理的根系活力显著高于CK(P0.05),其他处理与CK无明显差异;T3处理的株高显著高于对照CK(P0.05),其他处理与CK间无显著差异,达到最佳的效果。     

小型猪复合麻醉剂对大鼠不同脑区突触体Ca^2＋，Mg^2＋-ATP酶活性的影晌

探讨Ca2＋，Mg2＋-ATP酶与小型猪复合麻醉剂全麻作用的关系，以判断该酶是否为该制剂作用的靶位之一。选取84只SD大鼠，先随机抽取12只为对照组，其余随机均分为高剂量小型猪复合麻醉剂组（腹腔注射7．5mg／kg）和低剂量小型猪复合麻醉剂组（腹腔注射5mg／kg），每个剂量组又随机均分为麻醉组、恢复I组和恢复Ⅱ组等3个亚纽。对照组腹腔注射生理盐水10mL／kg，5min后断头取材；麻醉组、恢复I组和恢复Ⅱ组分别在翻正反射消失即刻、翻正反射恢复即刻和大鼠可直线爬行后断头取材，在生理盐水冰面上取脑，用4℃生理盐水将脑上的血迹冲洗干净，迅速分离双侧大脑皮层、海马、小脑、脑干、丘脑，立即液氮冷冻。制备脑粗突触体，采用比色法测定ca2＋，Mg2-ATP酶活性。结果表明，小型猪复合麻醉剂的全麻作用与抑制小脑和丘脑突触体Ca2＋，Mg2＋-ATP酶活性相关，此酶可能是小型猪复合麻醉剂全麻作用的靶位之一。     

钙处理桃果肉钙离子的分布及其与果实品质形成的关系

为探讨钙元素对桃果实品质、耐贮藏性的影响,确定最佳的叶面喷施钙元素的浓度,研究了喷施钙后,桃果肉组织中钙元素的分布特征、叶片叶绿素的含量以及对果实可溶性固形物含量(SSC)、大小、硬度和耐贮藏性的影响。结果表明,果肉中Ca2 的含量随着喷施钙元素浓度的提高而增加,当喷施CaCl2浓度为0.5%时叶绿素的含量最大,当喷施CaCl2浓度为1%时,SSC、果实大小和果肉硬度达到最大值；当喷施CaCl2浓度为2%时,放置3天后果实硬度最大。本研究确立了最佳的喷施浓度,为深入研究果实钙离子浓度梯度在果实品质形成方面的作用提供了依据。     

Dietary calcium/phosphorus ratio influences the efficacy of microbial phytase on growth,mineral digestibility and vertebral mineralization in juvenile tiger puffer,Takifugu rubripes

A 2 × 3 factorial feeding trial was conducted to determine effects of dietary Ca/P ratio and dietary microbial phytase on growth, mineral digestibility and vertebral mineralization in tiger puffer. The treatments consisted of three levels of Ca/P ratios (0.5, 1.0 and 1.5) combined either with phytase (2000 FTU kg^?1 diet) or without supplementation, respectively. The Ca/P ratios were achieved by supplementing calcium at 0, 6 and 12 g kg^?1 combined with the same level of inorganic P at 5 g kg^?1. After a 50‐day feeding trial, puffer fish fed the diet at low Ca/P ratio (0.5) together with phytase had significantly higher growth rate and feed intake (FI) than other groups. Both dietary Ca/P ratio and phytase supplement were independent effects on plasma minerals and alkaline phosphatase. Interactive effect between both dietary treatments was observed on P and Zn contents in vertebrae and whole body. P and Zn digestibilities tended to increase with increased Ca/P ratio from 0.5 to 1.0, especially when phytase was supplemented. In conclusion, fish fed a diet with highest Ca/P ratio (1.5) showed the poorest growth performance and nutrients utilization. Dietary Ca/P ratio of 0.5 (without Ca supplement) with 2000 FTU phytase per kg would be the optimum combination in the diet of tiger puffer.     

Evidence of diadromy in the French Polynesian Kuhlia malo (Teleostei: Percoidei) inferred from otolith microchemistry analysis

Abstract – Strontium/Calcium (Sr/Ca) and Barium/Calcium (Ba/Ca) ratios were measured in 60 otoliths of the French Polynesian flagtail Kuhlia malo. Both elemental ratios were needed to correctly distinguish residence in marine, brackish and fresh water. High Sr/Ca and low Ba/Ca around the nucleus of all otoliths provided evidence of marine residency during the early life of all individuals. At about 0.5 mm from the core, Ba/Ca increased rapidly and remained high in all otoliths. High and unstable Sr/Ca ratios were attributed to estuarine residency, whereas low and stable Sr/Ca ratios were attributed to freshwater residency. These chemical signatures inferred that following recruitment to rivers, some fish remained in the estuary, while others moved upstream. Some individuals shared their time between fresh and brackish waters later in life. The findings of this study have important implications for the protection of nearshore, brackish and freshwater environments for the conservation of this French Polynesian diadromous species.