Natural variation of potato <Emphasis Type="Italic">allene oxide synthase 2</Emphasis> causes differential levels of jasmonates and pathogen resistance in <Emphasis Type="Italic">Arabidopsis</Emphasis>

Natural variation of plant pathogen resistance is often quantitative. This type of resistance can be genetically dissected in quantitative resistance loci (QRL). To unravel the molecular basis of QRL in potato (Solanum tuberosum), we employed the model plant Arabidopsis thaliana for functional analysis of natural variants of potato allene oxide synthase 2 (StAOS2). StAOS2 is a candidate gene for QRL on potato chromosome XI against the oömycete Phytophthora infestans causing late blight, and the bacterium Erwinia carotovora ssp. atroseptica causing stem black leg and tuber soft rot, both devastating diseases in potato cultivation. StAOS2 encodes a cytochrome P450 enzyme that is essential for biosynthesis of the defense signaling molecule jasmonic acid. Allele non-specific dsRNAi-mediated silencing of StAOS2 in potato drastically reduced jasmonic acid production and compromised quantitative late blight resistance. Five natural StAOS2 alleles were expressed in the null Arabidopsis aos mutant under control of the Arabidopsis AOS promoter and tested for differential complementation phenotypes. The aos mutant phenotypes evaluated were lack of jasmonates, male sterility and susceptibility to Erwinia carotovora ssp. carotovora. StAOS2 alleles that were associated with increased disease resistance in potato complemented all aos mutant phenotypes better than StAOS2 alleles associated with increased susceptibility. First structure models of ‘quantitative resistant’ versus ‘quantitative susceptible’ StAOS2 alleles suggested potential mechanisms for their differential activity. Our results demonstrate how a candidate gene approach in combination with using the homologous Arabidopsis mutant as functional reporter can help to dissect the molecular basis of complex traits in non model crop plants.     

昆虫足的附着机制

昆虫卓越的爬行和附着能力来源于其精细的功能性黏附系统。根据形态结构的不同,昆虫的黏附系统可分为光滑型黏附垫和刚毛型黏附垫两种类型,二者在分泌液的支持下均能附着于几乎所有的光滑或粗糙的物体表面,而且这两种类型的黏附垫与界面的附着的形成均主要依赖于范德华力。本文综述了昆虫足的附着机制,包括光滑型和刚毛型两种黏附垫的结构和其形成附着的机理,以及黏附垫分泌液的功能、组成成分和释放机制,阐明了昆虫如何巧妙地解决稳定附着和快速脱附这一矛盾的问题,讨论了诸如界面的理化性质和环境湿度等环境因素对昆虫附着的影响,以期帮助人们深入地理解昆虫足的附着机制,并为其在仿生学等方面的应用提供理论依据。     

A hexapedal jointed-leg model for insect locomotion in the horizontal plane

We develop a simple model for insect locomotion in the horizontal (ground) plane. As in earlier work by Seipel et al. (Biol Cybern 91(0):76–90, 2004) we employ six actuated legs that also contain passive springs, but the legs, with “hip” and ‘knee’ joints, better represent insect morphology. Actuation is provided via preferred angle inputs at each joint, corresponding to zero torques in the hip and knee springs. The inputs are determined from estimates of foot forces in the cockroach Blaberus discoidalis via an inverse problem. The head–thorax–body is modeled as a single rigid body, and leg masses, inertia and joint dissipation are ignored. The resulting three degree-of-freedom dynamical system, subject to feedforward joint inputs, exhibits stable periodic gaits that compare well with observations over the insect’s typical speed range. The model’s response to impulsive perturbations also matches that of freely-running cockroaches (Jindrich and Full, J Exp Biol 205:2803–2823, 2002), and stability is maintained in the face of random foot touchdowns representative of real insects. We believe that this model will allow incorporation of realistic muscle models driven by a central pattern generator in place of the joint actuators, and that it will ultimately permit the study of proprioceptive feedback pathways involving leg force and joint angle sensing.     

Leg rings impact the diving performance of a foot-propelled diver

Leg rings are frequently used to mark aquatic birds in order to identify individuals, and study population dynamics and migration patterns, with the proviso being that the rings should not affect the birds. The effects of tags and rings are of particular interest in diving birds because any change in body shape could impact swimming efficiency and costs, as water is almost a thousand times denser than air. We attached tri-axial accelerometers to both ringed and unringed breeding Imperial Shags Leucocarbo atriceps to assess dive performance based on descent angle, descent rate, power stroke rate, power stroke peak acceleration amplitude and Vectorial Dynamic Body Acceleration (VeDBA) as a proxy for energy expenditure. Ringed birds, especially females, had a higher foot-stroke amplitude than unringed animals. In addition, the overall efficiency of the ringed individuals, as expressed by the descent rate per unit VeDBA, was compromised (by 3.5% in females and 4.3% in males) compared with unringed birds. We conclude that leg rings change the diving performance of Imperial Shags, although the effect is small and may not affect reproductive success. However, given that birds are typically ringed for life, we urge researchers to be particularly careful about the potential cumulative effect of attaching leg rings to foot-propelled diving species.     

牛蛙腐皮-红腿病并发症致病菌研究Ⅱ.荧光假单胞菌的分离和鉴定

对牛蛙腐皮 -红腿病并发症致病菌进行了分离、鉴定和人工感染试验 .从病蛙分离出 4株细菌 ,通过对健康幼蛙的人工感染试验 ,奇异变形杆菌和克氏耶尔森氏菌独立致发牛蛙腐皮病 ;嗜水气单胞菌和荧光单胞菌独立致发牛蛙红腿病 ,且都是通过伤口感染 .初步认为牛蛙患腐皮—红腿病并发症 ,是由于奇异变形杆菌、嗜水气单胞菌或克氏耶尔森氏菌与荧假单胞菌合并感染所致     

Notch-Mediated Segmentation and Growth Control of the Drosophila Leg

The possession of segmented appendages is a defining characteristic of the arthropods. By analyzing both loss-of-function and ectopic expression experiments, we show that the Notch signaling pathway plays a fundamental role in the segmentation and growth of the Drosophila leg. Local activation of Notch is necessary and sufficient to promote the formation of joints between segments. This segmentation process requires the participation of the Notch ligands, Serrate and Delta, as well as Fringe. These three proteins are each expressed in the developing leg and antennal imaginal discs in a segmentally repeated pattern that is regulated downstream of the action of Wingless and Decapentaplegic. Our studies further show that Notch activation is both necessary and sufficient to promote leg growth. We also identify target genes regulated both positively and negatively downstream of Notch signaling that are required for normal leg development. Together, these observations outline a regulatory hierarchy for the segmentation and growth of the leg. The Notch pathway is also deployed for segmentation during vertebrate somitogenesis, which raises the possibility of a common origin for the segmentation of these distinct tissues.     

Is the spinule pattern on the leg 4 coxopodite a tactile signal in the specific mate recognition system of Mesocyclops (Copepoda, Cyclopidae)?

Several recent observations on e.g. birds and fruit flies support the hypothesis that when previously geographically separated populations, as neospecies, come into contact, sexual isolation mechanisms become stronger as a result of direct selection against inferior hybrids (reinforcement hypothesis). Many aspects of the reproductive biology of cyclopid copepods are still very poorly known. However, all reports on mating processes in the genus Mesocyclops confirm that males attach to the fourth legs of the females by their geniculate antennulae before transferring spermatophores. Accordingly, it is reasonable to assume that the signals helping recognition of the conspecific mates are located on the leg 4 of the females. The posterior surface of the leg 4 coxopodite in Cyclopidae is ornamented with a complex and diverse spinule pattern which, despite some infraspecific variability, is a reliable species-specific trait in species of Mesocyclops. Depending upon whether the spinule ornamentation has any role in the recognition system, and whether it evolved in geographically separated populations or later when they had begun to overlap, different predictions can be made about the zoogeographical pattern of differences among these character states. In the following study, comparisons are made for 10 allopatric, four sympatric and two partially sympatric species pairs. These comparisons reveal that the degree of divergence in the spinule ornamentation is significantly greater between sympatric than between allopatric species. These results argue in favor of the spinule ornamentation of the leg 4 coxopodite being a signal in specific mate recognition system (SMRS), and that the divergence of this state is initiated when previously separated populations, as neospecies, begin secondary contact.     

Altered biomechanical strategies and medio-lateral control of the knee represent incomplete recovery of individuals with injury during single leg hop

Anterior cruciate ligament (ACL) injury can result in failure to return to pre-injury activity levels and future osteoarthritis predisposition. Single leg hop is used in late rehabilitation to evaluate recovery and inform treatment but biomechanical understanding of this activity is insufficient.     

Effects of Exercise Intensity on Physical Fitness and Risk Factors for Coronary Heart Disease

Objective: To determine whether “low‐intensity” exercise (walking) and “high‐intensity” exercise (aerobic dance), when added to a weight loss diet, have different effects on coronary heart disease (CHD) risk factors and physical fitness. Research Methods and Procedures: Ninety obese women were divided into diet only (DO), diet plus walking (DW), and diet plus aerobic dance (DA) groups. DXA was used to evaluate segmental body composition. Leg‐extension strength and maximal oxygen uptake (V?o _2max) were the indicators of physical fitness. Blood pressure, lipoproteins, and fasting glucose were used as indices for CHD risk factors. These items were measured before and after a 14‐week intervention period. Results: Whole‐body plus all segmental fat masses were significantly reduced (p < 0.001). Reductions in whole‐body and lower‐limb fat‐ and bone‐free masses were significantly less (p < 0.01) in the DA group (?1.5 and ?0.1 kg, respectively) compared with the DO (?2.1 and ?0.4 kg, respectively) and DW (?2.5 and ?0.5 kg, respectively) groups. Improvements in leg‐extension strength and V?o _2max were significantly greater (p < 0.05) in the DA group compared with the DO group. The CHD risk factors clearly improved (p < 0.05) within each group. Reductions in low density lipoprotein‐cholesterol and fasting glucose were significantly greater (p < 0.05) in the DA group compared with the DO and DW groups. Discussion: Adding higher intensity aerobic dance to a weight‐loss diet program may help maintain fat‐ and bone‐free mass and may be more effective in improving CHD risk factors compared with low‐intensity walking.