Plant development: regulation by protein degradation

Many aspects of eukaryotic development depend on regulated protein degradation by the ubiquitin-proteasome pathway. This highly conserved pathway promotes covalent attachment of ubiquitin to protein substrates through the sequential action of three enzymes called a ubiquitin-activating enzyme (E1), a ubiquitin-conjugating enzyme (E2), and a ubiquitin-protein ligase (E3). Most ubiquitinated proteins are then targeted for degradation by the 26S proteasome. Recent studies have also shown that the ubiquitin-related protein RUB/Nedd8 and the proteasome-related COP9 signalosome complex cooperate with the ubiquitin-proteasome pathway to promote protein degradation. Most of these components are conserved in all three eukaryotic kingdoms. However, the known targets of the pathway in plants, and the developmental processes they regulate, are specific to the plant kingdom.     

Crayfish muscle receptor organ: role in regulation of postural flexion

Recordings were made from postural-control motor nerves with antagonistic functions in the crayfish abdomen through flexible suction electrodes. During unrestrained flexion of the abdomen, output from the tonic stretch receptor neuron of RM(1),(SR(1)) is sufficient to drive an extensor motor unit in the same segment. However, this intrasegmental "resistance" reflex is normally blocked by an intersegmental reflex in which output from SR(1)'s in caudal segments inhibits SR(1) discharge in more anterior segments.     

Human embryonic kidneys in organ culture: abnormalities of development induced by decreased potassium

Human embryonic kidneys of 5 to 12 weeks of gestation were grown in organ culture. Potassium concentrations of 3 to 6 milliequivalents per liter produced decreased ureteral bud branching, failure of nephron induction, and occasional cystic dilatations of the ureteral bud. Normal development of the kidney occurred at potassium concentrations of 6.5 to 10 milliequivalents per liter. These studies confirm the importance of relative stability of the potassiunm concentration in the development of the embryonic kidney.     

Pheromone source location by flying moths: a supplementary non-anemotactic mechanism

After the wind was stopped in an insect flight tunnel, male oriental fruit moths continued to fly in zigzag fashion along a stationary pheromone plume. Their lateral excursions from the time-averaged pheromone plume were no greater without wind than in wind of 38 centimeters per second. When the pheromone plume was removed and the wind stopped, males initiated wider track reversals when they reached the pheromone-free area in still air than they had made while in the pheromone plume. This non-anemotactic mechanism of maintaining plume contact-possibly a special kind of klinotaxis-when coupled with the orthokinetic retinal velocity of apparent ground pattern motion, allowed males to reach the pheromone source area from 1 to 2 meters away without wind.     

No organ left behind: tales of gut development and evolution

The function of an organ is dependent on its cellular constituents as well as on their assembly into a cohesive unit. The developing gut faces unique challenges as one of the longest and largest organs in the body and also because it is constantly interfacing with external factors through the diet. Its location deep within the body has until recently hampered investigation into its formation. The patterning of the gut along its longitudinal, dorsoventral, left-right, and radial axes is one of the fascinating issues that pertain to the development, function, and homeostasis of this understudied organ.     

Control of spiracles in silk moths by oxygen and carbon dioxide

Spiracles of insects open in high carbon dioxide tensions and close in high oxygen tensions. However, the targets of these gases in insects have never been identified. In diapausing pupae of the cecropia silk moth carbon dioxide acts primarily and directly on the spiracular apparatus itself (muscle or neuromuscular junctions), whereas oxygen has as its primary target the central nervous system. The spiracle behaves as an independent effector in response to carbon dioxide; this is quite different from the situation in vertebrates, where carbon dioxide acts primarily on the central nervous system. The roles of various nerves in controlling spiracular activity are discussed.     

MADS-box基因家族调控植物花器官发育研究进展

花器官的发生发育与形态构造是一个高度复杂的项目,涉及众多因素及其相互作用,MADS-box基因作为其中的关键转录因子可以改变整个发育过程,因而成为花器官研究最广泛的基因家族.通过梳理目前MADS-box基因对花器官发生、分化和形态建成方面的调控作用,为了解花发育程序和该基因家族的一般转录调控机制提供新见解,也为进一步深...     

紫外分光光度法测定柞蚕雄蛾营养液中睾丸酮的含量

用紫外分光光度法测定柞蚕雄蛾营养液中睾丸酮的含量为3.892μg/m l,检测波长为242 nm,线性范围为2.0~20.0μg/ml,r=0.999,样品回收率为99.82%(n=5),RSD值为0.76%。此法与高效液相色谱法相比,方法简便,实验成本低,且结果准确,重现性好。     

Requirement for RORgamma in thymocyte survival and lymphoid organ development

Most developing thymocytes undergo apoptosis because they cannot interact productively with molecules encoded by the major histocompatibility complex. Here, we show that mice lacking the orphan nuclear hormone receptor RORgamma lose thymic expression of the anti-apoptotic factor Bcl-xL. RORgamma thus regulates the survival of CD4+8+ thymocytes and may control the temporal window during which thymocytes can undergo positive selection. RORgamma was also required for development of lymph nodes and Peyer's patches, but not splenic follicles. In its absence, there was loss of a population of CD3-CD4+CD45+ cells that normally express RORgamma and that are likely early progenitors of lymphoid organs. Hence, RORgamma has critical functions in T cell repertoire selection and lymphoid organogenesis.     

Insect photoreceptor: an internal ocellus is present in sphinx moths

Adult sphinx moths lack external ocelli. In Manduca sexta and other anocellate moths structures homologous to ocelli have been observed. Histological examination of such a structure in Manduca sexta has shown structural similarities to ocelli of other insects. Electrophysiological studies revealed a response to light stimuli stimilar to the electroretinogram of external ocelli. The evidence strongly suggests that the structures are internal ocelli.     

Polyol pathway in aorta: regulation by hormones

Aldose reductase is present in human and rabbit aortas and provides a mechanism whereby hyper-glycemia can alter the metabolism of the arterial wall. Aortic sorbitol concentration is regulated by ambient glucose concentration and is increased by epinephrine, isoproterenol, dibutyryl-3',5'-adenosine monophosphate, ouabain, and angiotensin II.     

Negative regulation of the SHATTERPROOF genes by FRUITFULL during Arabidopsis fruit development

The terminal step of fruit development in Arabidopsis involves valve separation from the replum, allowing seed dispersal. This process requires the activities of the SHATTERPROOF MADS-box genes, which promote dehiscence zone differentiation at the valve/replum boundary. Here we show that the FRUITFULL MADS-box gene, which is necessary for fruit valve differentiation, is a negative regulator of SHATTERPROOF expression and that constitutive expression of FRUITFULL is sufficient to prevent formation of the dehiscence zone. Our studies suggest that ectopic expression of FRUITFULL may directly allow the control of pod shatter in oilseed crops such as canola.     

Induction in vitro of microtubular crystals by vinca alkaloids

The addition of vinblastine or vincristine to solutions of pure microtubule protein or to supernatants from high-speed centrifugation of rabbit-brain homogenates results in the formation of a fine precipitate. Examination of this precipitate by electron microscopy reveals ordered structures with areas of ladder-like configuration.     

兰花花器官及成花基因调控研究进展

为了更有效地对开花植物中最大家族之一的兰科(Orchidaceae)植物进行开花调控,对具有蕊柱和唇瓣等独特花结构的兰花花器官调控和成花过程的分子遗传基础进行了阐述,并在此基础上对兰科花发育的调控进行了展望。结果表明:1)兰花花器官ABCDE模型中,A和E类基因决定萼片,A、B和E类基因决定花瓣,B、C和E类基因决定雄蕊,而D和E类基因决定心皮;2)温度、光周期和激素是决定兰花花起始和发育的关键;3)成花过程中的转录组、基因组以及功能基因验证的研究,取得了较大的突破。综上,本研究可为兰花花发育的分子遗传基础研究开辟新的思路。     

植物花器官发育模型及相关转录因子的研究

论述了有关花器官发育的ABCDE模型的最新进展以及四聚体模型,并对花发育相关的转录因子的研究进展进行了总结,以期为了解花发育的分子机理和遗传基础打下基础.     

厚皮甜瓜腔内种子的生长发育规律

[目的]分析厚皮甜瓜腔内种子的生长发育规律,为提高厚皮甜瓜制种产量和质量提供参考依据.[方法]以具有腔内种子发芽特性的厚皮甜瓜自交系05-6为试验材料,分析授粉后果实腔内种子的生长发育规律、腔内种子发芽的发生时期和变化趋势,比较不同授粉天数果实腔内种子的饱满程度、数量、发芽率、成苗率和幼苗健壮程度差异.[结果]厚皮甜瓜腔内种子成熟时间比果实成熟时间早,授粉后第26 d种子已充分饱满.其中,未发芽种子的饱满度、数量、发芽和成苗能力及成苗的健壮程度与授粉后第35 d(即果实完全成熟时)相比差异不显著(P>0.05);已发芽种子数量显著少于授粉后第35 d腔内发芽种子数量(P<0.05).[结论]提前摘瓜采种是降低厚皮甜瓜腔内种子发芽率的有效措施,厚皮甜瓜材料05-6的适宜采种时间为授粉后第26 d.     

卵泡生长发育及其调控的研究进展

综述了卵泡生长发育的动态模式,即卵泡经原始卵泡、初级卵泡、次级卵泡和窦腔卵泡发育至排卵卵泡的过程,着重阐述了卵泡生长发育过程中的调控机制,为进一步研究卵泡的生长、发育和排卵机制提供了理论基础。