生物节律与生物钟(下)

三、生物节律的研究进展和成因探索也许有人会问,把繁杂的生物节律归纳为生态节律,生理节律以及心理节律和免疫节律,生态节律又进一步分为基本节律和近似节律等等,这看起来似乎是生物节律的成因分类,那么生物节律的成因又     

极端环境下的生物节律

生物节律是生物为了适应地球自转产生的昼夜交替而进化出的生命活动调节机制。从植物的光合作用和叶片开合，到哺乳动物的睡眠、觉醒、进食、代谢、激素分泌和体温变化等，都受到生物节律的调节。一般认为，内源性的节律较为稳定，并且具有温度补偿效应。中枢节律由外界光照条件所同步化；外周组织的节律如何受中枢调控，也受到机体自身代谢反馈的影响。然而，在某些极端环境下，例如长期处于极昼极夜的两极地区、氧气含量低且气温变化无常的高原地区、干旱且气温变化范围极大的沙漠地区、常年不见阳光的深海和完全脱离地球自然环境和重力的太空，除了光照之外的其他环境因素也会对整个机体的节律产生影响；长期在这些极端环境下生存的生物也由于自然选择，进化出了相关基因的多态性以及独特的节律表型。本综述将讨论光照、低氧环境和温度影响生物节律的分子机制，并总结对于两极、高原、沙漠地区，以及深海、太空中动物的生物节律在个体和分子层面上的研究。这些研究或许可以帮助更好地理解生物体如何适应极端环境，为需要在极端环境下开展工作的人们如何调整作息状态提供一定的参考。     

动物内源褪黑素调控生物节律的研究进展

内源褪黑素对人类和其他哺乳动物的节律行为具有调控功能。生物节律是自然进化赋予生命的基本特征之一,生物体的生命活动受到生物节律的控制与影响。在哺乳动物中,节律调控中心是松果体,其主要功能是合成和分泌褪黑素。褪黑素广泛参与生物体节律行为的调节,本文从褪黑素的产生和作用机制,分别阐述褪黑素对昼夜节律行为和多种年节律行为的调控作用,同时明确褪黑素与生物钟及神经内分泌系统的直接作用和反馈互动的复杂集合,进一步揭示褪黑素调控生物节律的重要作用,以期为褪黑素的基础研究以及未来探究生物体的生物钟内源性发生机制提供参考。     

生物节律基因非编码RNA调控机制

节律性的振荡不仅存在于生物节律中枢也存在于外周器官、组织及细胞中,其产生依赖于节律基因的转录、转录后及翻译后水平调控。近几年,生物节律转录后水平调控机制研究成为热点。非编码RNA(ncRNAs)调控组分小RNA(microRNA)与长链非编码RNA(lncRNA)作为参与转录后调控的重要分子,已有研究表明microRNA与lncRNA调控节律基因mRNA与蛋白的相位及振幅。本文概述microRNA与lncRNA参与昼夜节律中枢与外周调控的研究进展,为生物节律转录后调控机制的进一步研究提供参考。     

NONO——代谢节律调节新分子

正生物节律(biological rhythm)指机体活动呈现的周期性变化;可分为日节律(circadian rhythm)、月节律(circamensual rhythm)、年节律(circannual rhythm)等;机体每昼夜间规律发生的节律性变化,被认为由"生物钟"调控;而"生物钟"则有其基因、分子与神经基础。生物节律具有自身调节性,以适应外界变化,增强生物的环境适应性。光照,摄食,温度等,均为重要的外界因素。摄食后,机体会发生一系列适应性变化,包括糖代谢水平上调、糖原合成增加等;然而,摄食影响机体生物节律的     

消化道营养物质吸收代谢昼夜节律性调控机制的研究进展

昼夜节律是指在生物体内存在的以近似24h为周期的生物节律.昼夜节律的重要性质之一是内源节律的周期性,哺乳动物的生理和代谢节律受昼夜节律的控制.昼夜节律的振荡导致下游分子通路和生理过程发生节律性变化,对营养物质的消化、吸收和代谢有一定的调控作用.本文主要综述了消化道蛋白质、糖、脂类等营养物质吸收代谢的节律性及其调控机制,...     

啮齿类动物的昼夜节律器及光周期对其影响机制

节律性（ｒｈｙｔｈｍｉｃｉｔｙ）是生命的基本特征之一,从单细胞生物到哺乳类动物的各种功能活动,生长繁殖乃至某些细微的形态结构,随着时间的推移都可能呈现某种有规律性的反复改变,这就是生物周期性,或生物节律性,亦称生物节律（ｂｉｏｌｏｇｉｃａｌｒｈｙｔ...     

生物节律和生物钟

从众多的生物节律现象可看出,动物、植物的生理机能和生活习性好象受体内某种内在的时钟控制,这种神秘的时钟称为“生物钟”,即生物感知时间的能力。而生物节律实际上是由生物钟控制的,是生物钟的外在表现。生物节律和生物钟的研究经历了3个主要阶段:50年代及以前的生物节律现象的描述阶段;60年代的模型建造阶段;70年代以来利用生物化学和分子     

蓝藻生物节律性分子调控机制的研究进展

生物钟现象是一种普遍存在于生物界细胞的内源节律性保持机制。生物钟机制的存在可以使生物体的代谢行为产生并维持以24 h为周期的昼夜节律,从而更好地适应于地球自转所产生的环境条件昼夜间节律性变化。蓝藻是目前生物钟分子机制研究中的模式生物,其依赖于k ai基因家族成员的核心生物钟调控模式已经被众多研究者详细阐明。蓝藻生物钟的核心振荡器是由蓝藻k aiA/B/C的编码产物来调控的,Kai蛋白的表达模式具有节律性。KaiC蛋白磷酸化状态的节律性循环及输入、输出途径相关组成蛋白的翻译后修饰状态节律性循环共同组成其反馈回路,负责维持生物钟节律性振荡的持续进行并与环境周期保持同步。传统的蓝藻生物钟分子机制模型认为,节律性表达基因翻译产物的转录/翻译负反馈抑制环是生物节律性维持和输出的关键。遗憾的是,在其它物种生物钟分子机制研究中未发现由kai基因家族成员同源基因组成的节律性标签,这表明以k aiA/B/C为核心振荡器的生物钟系统并不是一种跨物种保守的生物钟系统。近期,人们发现非转录/翻译依赖的振荡器(NTO)也具有成为生物节律性产生和维持的“源动力”的可能。过氧化物氧化还原酶(PRX)氧化还原状态节律性是第一种被报道的跨物种保守的NTO节律性标签,这也日渐成为蓝藻生物钟分子机制研究新的热点。     

A re-examination of the role of the nucleus in generating the circadian rhythm in Acetabularia.

The role of the nucleus in the generation of the circadian rhythm in Acetabularia has been nuclear. Early experiments showed that the plant could exhibit a circadian rhythm in the absence of a nucleus. However, other experiments appeared to show that the nucleus could impart phase information to the rhythm, and so therefore must be a part of the system that generates the rhythm. We have conducted experiments similar to these--in particular, one in which the nuclear end of the plant was entrained on a light-dark cycle that was opposite that of the rest of the plant. The phase of the free-running rhythm of this type of plant is not consistent with the conclusion that the nucleus is part of the circadian oscillator. We have also tried entraining opposite ends of plants with no nuclei on opposite light-dark cycles. The ultimate phases of these plants appear to be nearly random. A possible interpretation of these experiments is discussed.     

The Circadian Rhythm of Leaf Movement of Coleus blumei x C. frederici, a Short Day Plant. I. Under Constant Light Conditions

A new instrument for the recording of leaf movement rhythm is described. Coleus blumei x C. frederici, a short day plant, exhibits a circadian rhythm of leaf movement. The period length of the free running rhythm is shortest in continuous darkness and is increased with an increase in the light intensity. The amplitude of the rhythm tends to damp in continuous bright light.     

Effects of irrigation rhythm on growth,fruit-set,yield and quality of egg plant (Solanum melongena) in southern France

Summary Responses of egg plant crop to 3 irrigation rhythms based on the daily potential evapotranspiration were investigated. Results showed that the shorter the rhythm (5 times per week) the better the plant growth expressed in terms of plant length (Fig. 2) and/or yield shown as fruit number (Fig. 3) or fruit fresh weight (Fig. 4). The twice per week rhythm gave the medium, whereas the 10 days one gave the least plant growth and yield. Also the frequent rhythm (5 times per week) gave an earlier crop presented as flower-setting (Table 2).The three rhythms did not show an effect on crop quality expressed as mineral content of leaf blades, petioles or fruits. But results showed that leaf blades usually have higher mineral content than the fruits especially with the micro elements. re]19750305     

Functional Synchronization of Biological Rhythms in a Tritrophic System

In a tritrophic system formed by a plant, an herbivore and a natural enemy, each component has its own biological rhythm. However, the rhythm correlations among the three levels and the underlying mechanisms in any tritrophic system are largely unknown. Here, we report that the rhythms exhibited bidirectional correlations in a model tritrophic system involving a lima bean, a pea leafminer and a parasitoid. From the bottom-up perspective, the rhythm was initiated from herbivore feeding, which triggered the rhythms of volatile emissions; then the rhythmic pattern of parasitoid activities was affected, and these rhythms were synchronized by a light switch signal. Increased volatile concentration can enhance the intensity of parasitoid locomotion and oviposition only under light. From the top-down perspective, naive and oviposition-experienced parasitoids were able to utilize the different volatile rhythm information from the damaged plant to locate host leafminers respectively. Our results indicated that the three interacting organisms in this system can achieve rhythmic functional synchronization under a natural light-dark photoperiod, but not under constant light or darkness. These findings provide new insight into the rhythm synchronization of three key players that contribute to the utilization of light and chemical signals, and our results may be used as potential approaches for manipulating natural enemies.     

Effect of planting date on flowering time in wheat

The time from seed germination to anthesis varied for spring wheat in experiments in climate chambers with plants grown hydroponically at different nitrogen regimes. Time to anthesis was related to the time of seed germination during the calendar year. Seed germinating earlier in the calendar year required a shorter time to anthesis compared to seed germinating later in the year, a pattern found for all the spring wheat cultivars investigated. Time to anthesis was also found to be independent of factors such as year in which the seed was produced, nitrogen regime used, or year or site of cultivation. We suggest the existence of an annual rhythm for flowering in spring wheat. This variation in time to flowering can be due either to external factors or more likely to an endogenous rhythm in the plant. When investigating plant processes, it is of importance to be aware of such a rhythm, since it may influence the results depending on when during the year the experiments are performed.     

A molecular link between autophagy and circadian rhythm in plants

Extremely high or low autophagy levels disrupt plant survival under nutrient starvation. Recently, autophagy has been reported to display rhythms in animals. However, the mechanism of circadian regulation of autophagy is still unclear. Here, we observed that autophagy has a robust rhythm and that various autophagy-related genes (ATGs) are rhythmically expressed in Arabidopsis. Chromatin immunoprecipitation (ChIP) and dual-luciferase (LUC) analyses showed that the core oscillator gene TIMING OF CAB EXPRESSION 1 (TOC1) directly binds to the promoters of ATG (ATG1a, ATG2, and ATG8d) and negatively regulates autophagy activities under nutritional stress. Furthermore, autophagy defects might affect endogenous rhythms by reducing the rhythm amplitude of TOC1 and shortening the rhythm period of CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1). Autophagy is essential for the circadian clock pattern in seedling development and plant sensitivity to nutritional deficiencies. Taken together, our studies reveal a plant strategy in which the TOC1-ATG axis involved in autophagy-rhythm crosstalk to fine-tune the intensity of autophagy.     

Some effects of photoperiod on larviposition and fresh weight-gain in Myzus persicae

ABSTRACT. The larviposition of adult apterous Myzus persicae previously entrained to LD 18:6 showed a marked rhythm both under LD 12:12 (on plants reared in LD 18:6) and under LL (on plants reared in LL). No rhythm was detectable in larviposition by adults reared in LL. Larviposition peaked towards the end of the photophase in LD 12:12. Fresh-weight gain also showed a circadian rhythm with the greatest weight increases during the photophase. Re-entrainment from LD 12:12 to DL 12:12 was not complete after 10 days. It is concluded that the changes in the light cycle did not affect the aphids through the plant.     

Phaseshifting of the photoperiodic flowering response rhythm in Pharbitis nil by red-light pulses

The control by light of the flowering response rhythm in the short-day plant Pharbitis nil Choisy cv. Violet was examined by giving a single pulse of light at various times between 1 and 6 h after a 24-h light period. When the first circadian cycle of the rhythm was monitored, it was found that a pulse of red light given at 1, 2 or 3 h into a 72-dark period caused a 1-h delay of the phase of the response rhythm, while a pulse at 6 h caused a 2-h delay. These results support the hypothesis that, when red-light pulses are given at hourly intervals, they are as effective as continuous light in preventing the onset of dark timing because they repeatedly return the rhythm to the circadian time at which it is apparently suspended in continuous light. The perception of and response to continuous light and red-light pulses are also briefly discussed.     

Contribution of C3 carboxylation to the circadian rhythm of carbon dioxide uptake in a Crassulacean acid metabolism plant Kalanchoë daigremontiana

During the endogenous circadian rhythm of carbon dioxide uptake in continuous light by a Crassula cean acid metabolism plant, Kalancho? daigremontiana, the two carboxylating enzymes, phosphoenolpyruvate carboxylase (PEPC) and ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco), are active simultaneously, although, until now, only the role of PEPC in generating the rhythm has been acknowledged. According to the established model, the rhythm is primarily regulated at the PEPC activity level, modulated by periodic compartmentation of its inhibitor, malate, in the vacuole and controlled by tension/relaxation of the tonoplast. However, the circadian accumulation of malic acid (the main indicator of PEPC activity) dampened significantly within the first few periods without affecting the rhythm's amplitude. Moreover, the amount of malate accumulated during a free-running oscillation was several-fold lower than the amount expected if PEPC were the key carboxylating enzyme, based on a 1:1 stoichiometry of CO(2) and malate. Together with the observation that rates of CO(2) uptake under continuous light were higher than in darkness, the evidence shows that C(3) carboxylation greatly contributes to the generation of rhythmic CO(2) uptake in continuous light in this 'obligate' CAM plant. Because the shift from predominantly CAM to predominantly C(3) carboxylation is smooth and does not distort the trajectory of the rhythm, its control probably arises from a robust network of oscillators, perhaps also involving stomata.