淀粉含量不同的玉米自交系籽粒淀粉积累及其关键酶活性

以2个高淀粉和2个低淀粉玉米自交系为材料,分析了玉米籽粒淀粉的动态积累规律,同时对高低淀粉玉米籽粒灌浆过程中淀粉生物合成关键酶活性的动态变化及其与淀粉积累动态的相关性进行讨论分析。研究结果表明:灌浆过程中4个自交系淀粉含量变化趋势均呈sigmoid型曲线。灌浆过程中ADPG-PPase(腺苷二磷酸葡萄糖焦磷酸化酶)、SSS(可溶性淀粉合成酶)、GBSS(颗粒结合淀粉合成酶)活性均呈单峰曲线变化,峰值都出现在20～30DAP(授粉后天数)。2个高淀粉自交系的Q酶(淀粉分支酶)活性也呈单峰曲线变化,峰值也出现在20DAP,而2个低淀粉自交系的Q酶活性则呈双峰曲线变化,2个峰值分别出现在15～20DAP和30～35DAP。4个自交系籽粒淀粉的积累速率与各自交系ADPG-PPase、SSS和GBSS的活性变化呈极显著正相关。各自交系关键酶活性之间,ADPG-PPase、SSS和GBSS三者间活性变化呈极显著正相关,这3种酶活性变化与Q酶活性变化也呈不同程度的正相关。     

花部重金属积累对植物-传粉昆虫互惠关系影响的研究进展

传粉昆虫急剧下降是当前全球生态学家最为关注的热点问题之一,全球气候变化、土地利用改变、生境破碎化以及工农业生产带来的有害物质如杀虫剂等均有重要影响。相比而言,土壤重金属污染对传粉昆虫的潜在影响缺乏深入评价。土壤重金属会进入植物组织如花部,在传粉过程中传递到传粉者体内,并通过影响传粉者行为改变植物雌雄适合度,全面梳理相关研究进展和存在的问题,有助于提升对重金属污染带来的生态后果的全面认识,了解动植物相互关系对环境变化的响应。本文结合前期的研究成果,从重金属在植物花部中的积累模式、花部重金属积累对植物雌雄适合度的影响、经花部报酬介导的重金属积累对蜂类传粉者传粉行为、生活史关键环节的影响等进行综述,以期为理解花部重金属积累对植物与传粉昆虫互惠关系的影响,进而拓展关于土壤重金属污染与传粉昆虫数量减少之间的内在联系的科学认识。     

模拟降雨条件下砾石含量对塿土工程堆积体坡面产流产沙的影响

为探究砾石含量对塿土堆积体坡面产流产沙的影响,采用室内人工模拟降雨试验,以土质坡面为对照,研究5种砾石含量(10%、20%、30%、40%、50%)堆积体坡面在不同降雨强度(1.0、1.5、2.0、2.5 mm·min^-1)下的产流产沙特征。结果表明:不同试验条件下的平均径流率在2.18～13.07 L·min^-1,不同雨强条件下平均径流率均在砾石含量10%(或20%)和50%时分别达到最大值与最小值;平均流速在0.06～0.22 m·s^-1,流速变化复杂,砾石含量越小,流速变幅越大,变异系数也越大,砾石含量10%时平均流速最大。砾石的存在可有效抑制产沙,最大减沙效益可达84.2%,雨强相较于砾石含量对平均产沙率的影响更大。偏相关分析表明,平均径流率、流速、产沙率均与砾石含量呈极显著负相关;平均产沙率与平均径流率、平均流速以及二者交互项均呈极显著线性函数关系,其中,与平均径流率的相关性最强。本研究可为塿土区工程堆积体水土流失治理和侵蚀模型的建立提供参考。     

Biodiversity growth on the volcanic ocean islands and the roles of in situ cladogenesis and immigration: case with the reptiles

Models for biodiversity growth on the remote oceanic islands assume that in situ cladogenesis is a major contributor. To test this, we compiled occurrence data for 194 terrestrial reptile species on 53 volcanically‐constructed middle‐ to low‐latitude landmasses worldwide. Despite 273 native island‐species records, there are only 8–12 cases of the phenomenon, including just two radiations. Diversification frequencies are largely uncorrelated with island area, age, maximum altitude, and isolation. Furthermore, there is no indication that the presence of non‐sister congeners on an island stymies the process. Diversity on individual oceanic islands therefore results primarily from immigration and anageneis, but this is not a simple matter. Clusters that are difficult to reach (far or challenging to get to) or thrive upon (e.g. Canaries, Galápagos) have relatively few clades (3–8), some of which have many species (6–14), and all host at least one endemic genus. In these settings, diversity grows mainly by intra‐archipelago transfer followed by within‐island anagenetic speciation. In contrast, those island groups that are easier to disperse to (characterized by short distances and conducive transit conditions) and harbour more benign habitats (e.g. Comoros, Lesser Antilles) have been settled by many ancestor‐colonizers (≥ 14), but each clade has few derived species (≤ 4). These archipelagoes lack especially distinctive lineages. Models explaining the assembly and growth of terrestrial biotic suites on the volcanic ocean islands thus need to accommodate these new insights.     

Hsp105α suppresses Adriamycin-induced cell death via nuclear localization signal-dependent nuclear accumulation

Heat shock protein 105 (Hsp105) is a molecular chaperone, and the isoforms Hsp105α and Hsp105β exhibit distinct functions with different subcellular localizations. Hsp105β localizes in the nucleus and induces the expression of the major heat shock protein Hsp70, whereas cytoplasmic Hsp105α is less effective in inducing Hsp70 expression. Hsp105 shuttles between the cytoplasm and the nucleus; the subcellular localization is governed by the relative activities of the nuclear localization signal (NLS) and nuclear export signal (NES). Here, we show that nuclear accumulation of Hsp105α but not Hsp105β is involved in Adriamycin (ADR) sensitivity. Knockdown of Hsp105α induces cell death at low ADR concentration, at which ADR is less effective in inducing cell death in the presence of Hsp105α. Of note, Hsp105 is localized in the nucleus under these conditions, even though Hsp105β is not expressed, indicating that Hsp105α accumulates in the nucleus in response to ADR treatment. The exogenously expressed Hsp105α but not its NLS mutant localizes in the nucleus of ADR-treated cells. In addition, the expression level of the nuclear export protein chromosomal maintenance 1 (CRM1) was decreased by ADR treatment of cells, and CRM1 knockdown caused nuclear accumulation of Hsp105α both in the presence and absence of ADR. These results indicating that Hsp105α accumulates in the nucleus in a manner dependent on the NLS activity via the suppression of nuclear export. Our findings suggest a role of nuclear Hsp105α in the sensitivity against DNA-damaging agents in tumor cells.     

Modelling time‐varying low‐temperature‐induced mortality rates for pupae of Tuta absoluta (Gelechiidae,Lepidoptera)

In a series of laboratory experiments, acclimated pupae of Tuta absoluta were exposed to various constant low temperatures in order to estimate their maximum survival times (Kaplan–Meier, Lt_99.99). A Weibull function was fitted to the data points, describing maximum survival time as a function of temperature. In another experiment at ?6°C, the progress of mortality increasing with exposure time was identified. These values were fitted by a sigmoidal function converging asymptotically to 100% mortality for very long exposure times. Analysing mortality data from the maximum survival experiment by a generalized linear model showed a significant common slope parameter (p < .001) that reveals parallelism of the survival curves at each temperature if a log time axis is used. These curves appear stretched (time scaled) if plotted with a nonlogarithmic time axis. By combining these mathematical relations, it was possible to calculate a species‐specific ‘mortality surface’ which exhibits mortalities, depending on temperature and duration of exposure. In order to accumulate hourly mortalities for courses of varying temperatures, an algorithm was developed which yields mortality values from that surface taking into account the attained mortality level. In validation experiments, recorded mortalities were compared against modelled mortalities. Prediction of mortality was partially supported by the model, but pupae experiencing intensely fluctuating temperatures showed decreased mortality, probably caused by rapid cold hardening during exposure. Despite this observation, mortality data converged to distinct levels very close to 100% depending on the intensity of temperature fluctuations that were characteristic for different types of experiments. The highest mortality limit occurred at intensely fluctuating temperatures in laboratory experiments. This constituted a benchmark that was not reached under various field conditions. Thus, it was possible to identify temperature limits for the extinction of field populations of Tuta absoluta pupae.     

Steroid accumulation in song nuclei of a sexually dimorphic duetting bird,the rufous and white wren

This study tested the hypothesis that the relative proportion of neurons that are hormone sensitive in avian song control nuclei is related to the basic motor ability to sing, whereas the absolute number of such neurons is related to the complexity of song behavior. Either [³H]testosterone (T) or estradiol (E₂) was injected into male and female rufous and white wrens (Thryothorus rufalbus), a tropical species in which females sing duets with males but have smaller song repertoires than males. Autoradiographic analysis indicated that there were no sex differences in the proportions of T or E₂ target cells in two song nuclei: the high vocal center (HVC) and the lateral portion of the magnocellular nucleus of the anterior neostriatum (IMAN). The density of labeled cells per unit volume of tissue did not differ between the sexes in either song nucleus. Males have larger song nuclei, however, which is consistent with their more complex song behavior, and therefore have a greater total number of hormone-sensitive neurons in these regions than do females. Comparison of these results with measures of hormone accumulation in zebra finches, canaries, and bay wrens supports the hypothesis presented. © 1996 John Wiley & Sons, Inc.     

均时作用——一个常见但不易识别的埋葬学现象

生物化石群落在埋葬过程中普遍经历了均时作用的过程。正是这种作用导致了同一生态环境域,但不同时期生物组合相混合的结果。因此,这种化石群落可能为一个连续演化群落的不同阶段的混合体,也可能是环境连续演化过程中不同生态群落的混合组合,这样的化石组合所记录的古生物学信息非常复杂。因此,对化石累积过程中的均时作用的清晰了解,将非常有助于古生物群落的分类学、居群动力学、埋葬学、古生态学、演化古生物学,甚至地层学研究精度的提高。文章根据前人的研究,扼要介绍和讨论均时作用的概念、过程、程度、效应和判别,及受均时作用影响的化石组合的分类。     

Peroxisome-generated succinate induces lipid accumulation and oxidative stress in the kidneys of diabetic mice

Diabetes normally causes lipid accumulation and oxidative stress in the kidneys, which plays a critical role in the onset of diabetic nephropathy; however, the mechanism by which dysregulated fatty acid metabolism increases lipid and reactive oxygen species (ROS) formation in the diabetic kidney is not clear. As succinate is remarkably increased in the diabetic kidney, and accumulation of succinate suppresses mitochondrial fatty acid oxidation and increases ROS formation, we hypothesized that succinate might play a role in inducing lipid and ROS accumulation in the diabetic kidney. Here we demonstrate a novel mechanism by which diabetes induces lipid and ROS accumulation in the kidney of diabetic animals. We show that enhanced oxidation of dicarboxylic acids by peroxisomes leads to lipid and ROS accumulation in the kidney of diabetic mice via the metabolite succinate. Furthermore, specific suppression of peroxisomal β-oxidation improved diabetes-induced nephropathy by reducing succinate generation and attenuating lipid and ROS accumulation in the kidneys of the diabetic mice. We suggest that peroxisome-generated succinate acts as a pathological molecule inducing lipid and ROS accumulation in kidney, and that specifically targeting peroxisomal β-oxidation might be an effective strategy in treating diabetic nephropathy and related metabolic disorders.     

嫁接诱导大豆低镉富集性状及遗传稳定性

通过野外小区实验,从8个大豆品种中筛选出2个低镉富集品种作为砧木,2个高镉富集品种作为接穗植物,研究嫁接当代以及接穗子代镉富集性状的变化,探明嫁接诱导镉富集性状变异的机制及其遗传稳定性.结果表明:大豆的镉富集性状表现出显著的品种间差异,以低镉富集品种(铁丰29和东鲜1号)作砧木,可以使接穗大豆植株(青仁黑1号和中黄38...