A bodyguard or a tastier meal? Dying caterpillar indirectly protects parasitoid cocoons by offering alternate prey to a generalist predator

In some parasitic Hymenoptera the dying caterpillars remain attached or close to the parasitoid cocoons. It has been suggested that the caterpillars act as ‘bodyguards’ for the vulnerable cocoons and therefore protect them against predators and/or hyperparasitoids (the ‘usurpation hypothesis’). This hypothesis has been demonstrated in associations where the caterpillars remain active and/or aggressive after parasitism. However, in other associations the caterpillars are so physiologically depleted after parasitism that they are unable to physically defend the cocoons and instead sit atop them in a moribund state. In this study a generalist predator, the spined soldier bug, Podisus maculiventris Say (Hemiptera: Pentatomidae), was provided with cocoons of the gregarious endoparasitoid Cotesia glomerata L. and the solitary endoparasitoid Microplitis mediator Haliday (both Hymenoptera: Braconidae), in turn attended by their hosts, Pieris brassicae L. (Lepidoptera: Pieridae) and Mamestra brassicae L. (Lepidoptera: Noctuidae), respectively. Cotesia glomerata produces broods of up to 40 cocoons and the dying caterpillars sit atop the cocoons where they exhibit little response to physical stimuli. Previous studies reported that dying P. brassicae caterpillars were ineffective bodyguards against two species of hyperparasitoids. In both associations, the dying host caterpillars were significantly preferred as food by P. maculiventris over the parasitoid cocoons. However, in absence of caterpillars, the bugs readily attacked the C. glomerata cocoons. Alternatively, the survival of M. mediator was very low, irrespective of whether a caterpillar was present or not. Caterpillars attacked by M. mediator are several times smaller than those attacked by C. glomerata. Consequently, the predators ran out of food much more quickly in the former and switched from one prey to the other. We show that in some host–parasitoid associations the dying caterpillars provide more visually apparent or nutritionally superior prey, rather than acting as bodyguards.     

Self‐rescue of an EXTENSIN mutant reveals alternative gene expression programs and candidate proteins for new cell wall assembly in Arabidopsis

Plants encode a poorly understood superfamily of developmentally expressed cell wall hydroxyproline‐rich glycoproteins (HRGPs). One, EXTENSIN3 (EXT3) of the 168 putative HRGPs, is critical in the first steps of new wall assembly, demonstrated by broken and misplaced walls in its lethal homozygous mutant. Here we report the findings of phenotypic (not genotypic) revertants of the ext3 mutant and in‐depth analysis including microarray and qRT‐PCR (polymerase chain reaction). The aim was to identify EXT3 substitute(s), thus gaining a deeper understanding of new wall assembly. The data show differential expression in the ext3 mutant that included 61% (P ≤ 0.05) of the HRGP genes, and ability to self‐rescue by reprogramming expression. Independent revertants had reproducible expression networks, largely heritable over the four generations tested, with some genes displaying transgenerational drift towards wild‐type expression levels. Genes for nine candidate regulatory proteins as well as eight candidate HRGP building materials and/or facilitators of new wall assembly or maintenance, in the (near) absence of EXT3 expression, were identified. Seven of the HRGP fit the current model of EXT function. In conclusion, the data on phenotype comparisons and on differential expression of the genes‐of‐focus provide strong evidence that different combinations of HRGPs regulated by alternative gene expression networks, can make functioning cell walls, resulting in (apparently) normal plant growth and development. More broadly, this has implications for interpreting the cause of any mutant phenotype, assigning gene function, and genetically modifying plants for utilitarian purposes.     

Natural genetic variation in male reproductive genes contributes to nontransitivity of sperm competitive ability in Drosophila melanogaster

Female Drosophila melanogaster frequently mate with multiple males, and the success of a given male depends not only on his genotype but also on the genotype of his competitor. Here, we assess how natural genetic variation affects male–male interactions for traits influencing pre‐ and postcopulatory sexual selection. Males from a set of 66 chromosome substitution lines were competed against each other in a ‘round‐robin’ design, and paternity was scored using bulk genotyping. We observed significant effects of the genotype of the first male to mate, the second male to mate and an interaction between the males for measures of male mating rate and sperm utilization. We also identified specific combinations of males who show nontransitive patterns of reproductive success and engage in ‘rock‐paper‐scissors’ games. We then tested for associations between 245 polymorphisms in 32 candidate male reproductive genes and male reproductive success. We identified eight polymorphisms in six reproductive genes that associate with male reproductive success independent of the competitor (experimentwise P < 0.05). We also identified four SNPs in four different genes where the relative reproductive success of the alternative alleles changes depending on the competing males' genetic background (experimentwise P < 0.05); two of these associations include premature stop codons. This may be the first study that identifies the genes contributing to nontransitivity among males and further highlights that ‘rock‐paper‐scissors’ games could be an important evolutionary force maintaining genetic variation in natural populations.     

Sperm competition in tropical versus temperate zone birds

Sperm competition represents an important component of post-copulatory sexual selection. It has been argued that the level of sperm competition declines in birds towards the equator. However, to date, sperm competition estimates have been available mainly for avian species inhabiting the northern temperate zone. Here we apply a novel approach, using the coefficient of between-male variation (CV_bm) in sperm size as an index for sperm competition risk, in a comparative analysis of 31 Afrotropical and 99 northern temperate zone passerine species. We found no difference in sperm competition risk between the two groups, nor any relationship with migration distance. However, a multivariate model indicated that sperm competition risk was highest in species with a combination of low body mass and few eggs per clutch. The effect of clutch size was most pronounced in tropical species, which indicates that sperm competition risk in tropical and temperate species is differently associated with particular life-history traits. Although tropical species had lower sperm competition risk than temperate zone species for overlapping clutch sizes, the idea of a generally reduced risk of sperm competition in tropical birds was not supported by our analysis.     

中国部分板栗品种坚果表型及营养成分遗传变异分析

以中国板栗主产区山东等10个省份97个板栗品种为材料,对其坚果表型性状及营养成分进行遗传变异分析。结果显示:（1）97个板栗品种间存在广泛的遗传变异,坚果表型性状及营养成分指标品种间差异均达到极显著水平;遗传变异系数均较大,最大达到0.378,遗传潜力较大;且所有性状重复力均在0.928及以上,受自身遗传因素控制较强。（2）坚果长度等表型性状间呈极显著正相关关系,淀粉含量等营养成分指标间为正相关关系,而表型性状与营养成分指标间表现为负相关关系,据此可将坚果表型性状、品质性状作为两个相互独立又有一定关联的综合因子。（3）进一步利用坚果表型和营养成分8个指标对97个板栗品种进行主成分分析,并结合多重比较结果,综合选出具有单个或多个性状优势的43个品种。研究认为,选出的43个板栗品种具有果粒较大,或营养价值较高,或二者特性兼有,初步选择为果型或品质优良的板栗品种资源材料。     

Subunits and Sulfhydryl Groups of Beef Liver d-Glycerate Dehydrogenase

The amino acid composition of beef liver d-glycerate dehydrogenase (EC 1.1.1.29) was determined. Results of sodium dodecyl sulfate gel electrophoresis and measurements of the number of NADH bound by the enzyme and the number of the essential sulfhydryl groups suggested that the enzyme was composed of two identical subunits with the molecular weight of 36,000. Close relation between the essential sulfhydryl groups and the coenzyme binding site was also suggested. Effect of an alkylating agent (bromopyruvate) with the structure similar to the substrate was studied. Effects of iodoacetate and iodoacetamide were also studied. It was suggested that these reagents behaved as active-site-directed irreversible inhibitors of the enzyme. Bromopyruvate exhibited a high affinity to the enzyme. Iodoacetate (anionic reagent) had a higher affinity than iodoacetamide (neutral reagent).     

模拟微重力对恶性胶质瘤细胞U87 影响的实验研究

目的:探讨模拟微重力(Modeled microgravity,MMG)对恶性胶质瘤细胞U87形态、生长增殖、基质金属蛋白酶-2、-9(Matrix metalloproteinase 2,MMP-2、Matrix metalloproteinase 9,MMP-9)及神经胶质酸性蛋白(Glial fibrillary acidic protein,GFAP)表达的影响。方法:常规培养U87细胞,传代培养3代后分为两组,正常重力组(Normal gravity,NG组)及模拟微重力干预组(Modeled microgravity,MMG组),相应条件下培养24 h,48 h和72 h。倒置显微镜观察U87细胞形态改变,细胞计数法及四甲基偶氮唑盐微量酶反应比色法(3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide,MTT法)检测模拟微重力干预和干预后U87细胞生长增殖情况;Western Blot检测不同培养时间后胶质瘤细胞U87 MMP-2、MMP-9及GFAP蛋白的表达情况。结果:模拟微重力条件下培养72 h后,U87细胞轮廓不规则,边缘圆钝,触角变少;模拟微重力条件下,U87细胞生长速度明显减慢,并且经模拟微重力干预48 h和72 h后的胶质瘤细胞经传代再培养,其增殖率也明显低于正常重力组;同时,U87细胞MMP-2及MMP-9蛋白表达水平与模拟微重力处理时间呈时间依赖性下降,而GFAP蛋白表达水平则呈时间依赖性升高。结论:模拟微重力影响U87细胞的形态、生长及表型。     

The chondrocyte-intrinsic circadian clock is disrupted in human osteoarthritis

Peripheral clocks are essential for driving cell differentiation. In osteoarthritis, loss of the normal differentiated chondrocyte (cartilage cell) phenotype is causative of disease. We investigated whether clock gene expression differed in osteoarthritic compared to “healthy” chondrocytes and used RNAi to determine whether the differences observed could affect chondrocyte phenotype. Following serum shock, PER2 expression was significantly higher, whereas BMAL1 expression was significantly lower, in osteoarthritic chondrocytes. Knockdown of BMAL1 in “healthy” chondrocytes was associated with higher cell proliferation and MMP13 expression, features characteristic of the osteoarthritic chondrocyte phenotype. Chondrocyte-intrinsic clock disruption may be a critical early step in osteoarthritis development.