提高稻瘟病菌转化频率的研究

 为提高pAN7-1质粒导入稻瘟病菌建立的遗传转化体系的转化率，进行了对转化效率影响因子的研究。稻瘟病菌转化溶液中使用50 mmol/L CaCl₂浓度，PEG4000 40%或PEG80000 40%多聚物，添加30 μg鲱鱼精DNA，供体质粒DNA呈直线状都有利转化频率的提高。其中鲱鱼精DNA作用尤为显著，由于添加30 μg鲱鱼精DNA，转化频率高达71.6转化子/μg DNA。42℃热冲击对稻瘟病菌转化并非必需，转化溶液中添加受体菌2539w DNA后，反而引起转化频率的明显下降。     

亚致死剂量苏云金杆菌蜡螟亚种对大蜡螟幼虫磷酸酶活力的影响

本文研究了亚致死剂量苏云金杆菌蜡螟亚种对大蜡螟幼虫磷酸酶活力的影响。结果表明,经苏云金杆菌蜡螟亚种(Bacillus thuringiensis galleriae)晶体蛋白处理后大蜡螟幼虫肠道酸性磷酸酶比活力升高,电泳分析表明肠道碱性磷酸酶活力降低,同功酶谱无明显变化。组织化学染色结果也表明,中肠细胞碱性磷酸酶活力下降。但幼虫血淋巴碱性磷酸酶活力及同功酶谱都没有明显变化。     

白僵菌感染桑天牛幼虫致病过程的显微观察

为了探讨白僵菌(Beauveria bassian)与寄主桑天牛(Apriona germari)间的相互作用方式及关系,采用扫描电镜观察了白僵菌分生孢子在桑天牛幼虫体表的侵染及穿透过程。结果表明,白僵菌分生孢子接种后8 h就可以附着于桑天牛幼虫体壁,12 h时可见孢子萌发产生芽管和附着胞,16 h即可穿透幼虫体壁;桑天牛幼虫体壁不同结构区影响白僵菌分生孢子萌发速度、附着胞形成以及芽管长度,与幼虫体壁的其它结构区相比,在幼虫体表节间膜处的白僵菌分生孢子萌发早,生长更快,并且孢子不会从幼虫体表的气孔侵入;已死亡虫体的表皮、气门均发生畸变。     

家蝇幼虫溶菌酶II基因的克隆、表达及抑菌活性研究

以本实验室构建的鸡致病性大肠杆菌诱导家蝇幼虫抑制性消减杂交文库(SSH)为基础,对家蝇幼虫溶菌酶II基因(MdL-II)进行克隆,得到全长为532 bp的cDNA片段,其开放阅读框(ORF)与GenBank中登录号为HQ897688.1的MdL-II基因全序列同源性为95%。将MdL-II ORF序列插入到pET-32a(+)表达载体中成功构建重组质粒,其表达产物经十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)分析,结果显示约在34 ku处出现表达条带且与目的蛋白大小相符。当诱导温度为37℃,IPTG浓度为0.6 mmol/L时可获得大量可溶性Trx-MdL-II融合蛋白,纯化融合蛋白并进一步检测该蛋白的抑菌活性,结果表明融合蛋白对大肠杆菌和链球菌均有抑菌作用,且对大肠杆菌的抑菌作用相对较强。     

黑水虻幼虫的保鲜工艺及货架期预测研究

为了得到黑水虻幼虫的保鲜工艺,对其净化、致死和减菌化处理方法进行了研究,同时进行了货架期预测.结果 表明:黑水虻幼虫加工方法为虫与水质量比1∶4,净化黑水虻幼虫48 h,每24 h换1次水;净化后热水70℃处理10 min、80℃处理5 min和90℃处理2 min均可使虫体致死,并且虫体较为美观;减菌化处理效果表明,加热杀菌效果最好,100℃杀菌10 min,杀菌率可达100％;利用ASLT法构建的Q10预测模型,预测得到黑水虻幼虫在4℃下作为食品和饲料的货架期分别为15.6 d和97 d.     

Factors controlling the early stages of viral haemorrhagic septicaemia epizootics: low exposure levels, virus amplification and fish-to-fish transmission

Viral haemorrhagic septicaemia virus, Genogroup IVa (VHSV), was highly infectious to Pacific herring, Clupea pallasii (Valenciennes), even at exposure doses occurring below the threshold of sensitivity for a standard viral plaque assay; however, further progression of the disease to a population‐level epizootic required viral amplification and effective fish‐to‐fish transmission. Among groups of herring injected with VHSV, the prevalence of infection was dose‐dependent, ranging from 100%, 75% and 38% after exposure to 19, 0.7 and 0.07 plaque‐forming units (PFU)/fish, respectively. Among Pacific herring exposed to waterborne VHSV (140 PFU mL^?1), the prevalence of infection, geometric mean viral tissue titre and cumulative mortality were greater among cohabitated herring than among cohorts that were held in individual aquaria, where fish‐to‐fish transmission was prevented. Fish‐to‐fish transmission among cohabitated herring probably occurred via exposure to shed virus which peaked at 680 PFU mL^?1; shed virus was not detected in the tank water from any isolated individuals. The results provide insights into mechanisms that initiate epizootic cascades in populations of wild herring and have implications for the design of VHSV surveys in wild fish populations.     

Molecular attempt to identify prey organisms of lobster phyllosoma larvae

ABSTRACT:   A molecular approach was adopted to investigate the natural diets of palinurid and scyllarid lobster phyllosoma larvae. The central domain of the 18S rDNA gene was amplified using nested polymerase chain reaction (PCR) and genomic DNA extracted from the larval hepatopancreas. The resulting 18S rDNA clones were screened using restriction fragment length polymorphism (RFLP) analysis, and then FASTA homology search and phylogenetic analysis were performed on the nucleotide sequences to identify the source of the eukaryotic organisms. The feasibility of this method was confirmed using the laboratory-reared phyllosoma larvae of the Japanese spiny lobster Panulirus japonicus that were fed either with common mussel Mytilus edulis gonads or with Artemia nauplii exclusively. Among the 804 clones isolated from five wild-caught mid- to late-stage phyllosoma larvae (three palinurids and two scyllarids), 0–132 clones per sample possessed restriction profiles distinct from those of the hosts. The Cnidaria and Urochordata DNA were identified from both the palinurid and the scyllarid larvae, which were thought to be prey animals for the mid- to late-stage phyllosoma larvae.     

Survival and growth of sardine larvae in the offshore side of the Kuroshio

After 1984 the major spawning of the Japanese sardine, Sardinops melanostictus, has been observed to occur in the offshore waters, where the survival of early-stage larvae (4–10 mm in length) is questionable. The main objective of this study is to estimate the growth and survival rates of the early-stage larval cohort in the offshore side of the Kuroshio Current. A radar-reflecting buoy with a surface drogue was launched to tag a patch of larvae, and the patch was traced for 3 days in March 1991. The survival rate of the early-stage larval cohort was calculated from the change in density during the survey. The range of the instantaneous mortality rate was from 0.83 to 1.11 day, a survival rate of32-44%day-¹.The mean density of the smaller larvae (4–6 mm in length) decreased more rapidly than that of the larger larvae (6–10 mm in length) during the sampling period. The survival rate of the first-feeding larvae in the offshore region seemed to be lower than that of the post-flrst-feeding larvae. However, the growth rates of the first-feeding larvae's survivors in the region were higher than those of the post-first-feeding larvae's survivors. The first-feeding larvae in the offshore region seemed to survive when the growth rate of the larvae was high.     

Chemical cues promote settlement in larvae of the green-lipped mussel, Perna canaliculus

The large (70,000 tonnes) mussel aquaculture industry for the endemic New Zealand green-lipped mussel, Perna canaliculus Gmelin, currently relies almost entirely (80%) on wild caught seed that is often harvested attached to great quantities of floating algae. Natural vagaries in catches of wild mussel seed frequently result in shortages of mussel seed that, at times, have severely affected commercial aquaculture production. Both field and laboratory experiments were used to establish that chemical cues derived from algae significantly increase settlement of mussel larvae on artificial substrates. This is the first time an algal chemical cue has been implicated in the settlement behavior of P. canaliculus larvae. These results have potential commercial implications for improving mussel seed supply through inducing higher or more reliable levels of mussel settlement for aquaculture seed collection.     

Differences in the total lipid and lipid class composition of larvae and metamorphosing sea lampreys, Petromyzon marinus

This study compared the alterations in total lipid and lipid class composition of kidney, liver, and intestine from sea lamprey, Petromyzon marinus, during their nontrophic metamorphosis with these parameters in unmetamorphosed larvae. Total lipid in kidney and liver initially was higher by 104 and 66%, respectively, in the earliest metamorphic stage (3) examined compared to larvae and then decreased by 73 and 37%, respectively, from stage 3 to stage 7. Total lipid in intestine, on the other hand, was 53% lower at stage 3 compared to larvae and then significantly increased by 260% from stage 3 to stage 7. Large amounts of triacylglycerol (TG) in kidney and liver implicate these organs as lipid depots; much of the change in total lipid content of kidney and liver could be explained by alterations in TG, although significant variations in other lipid classes (e.g., phospholipid, cholesterol) also were noted. These results suggest that lamprey metamorphosis may proceed in two metabolic phases in a tissue-specific manner and that lipid depletion results from specific catabolism of stored TG reserves.