Cloning and Characterization of Putative Hd6 Ortholog Associated with Zea mays L.Photoperiod Sensitivity

The photoperiod response of fowering is critical to the survival and successful reproduction in crops.The Hd6 gene,encoding a protein similar to the Arabidopsis α-subunit of CASEIN KINASE2α(CK2α)has been reported to affect flowering time through the photoperiodic pathway in rice.In this study,the maize ortholog,ZmHd6,has been cloned and its role in the photoperiodic pathway was investigated.ZmHd6 encodes 332 amino acids with six distinct domains: two CK2 active domains,a nuclear localization signal sequence,a N terminal domain,an ATP binding site,and an active site of serine/threonine protein kinase.ZmHd6 was constitutively expressed in the leaves and shoot apical meristem(SAM)with the highest expression in SAMs of plants with seven leaves under long and short day conditions.Delayed flowering time under long day(LD)conditions were observed in ZmHd6 overexpression transgenic Arabidopsis plants compared to the wild type.In transgenic Arabidopsis plants,ZmHd6 was expressed in a circadian oscillatory pattern,TOC1 peak expression was delayed,new G1,CO,and FT expressions reached to peak after 3 h while entering illumination period and oscillatory expression patterns of CO and FT were created during the dark phase.These results suggested that ZmHd6 might negatively regulate flowering time under LD conditions by delaying TOC1 peak expression and disrupting CO and FT expression in transgenic Arabidopsis plants.     

碳酸盐碱度对中华蟾蜍蝌蚪生长发育的影响

[目的]研究碳酸盐碱度对中华蟾蜍蝌蚪生长发育的影响,为其他水生生物的生长对碳酸盐碱度的适应性研究提供数据与参考。[方法]以中华蟾蜍蝌蚪为试材,研究蝌蚪在碱性不同水平值上中毒反应的变化规律,从而找出致死量和安全量。[结果]碳酸盐碱度对中华蟾蜍的24、48、72、96h零致死量（LD0）分别为9．97、8．85、6．23、3．84mmol／L,10％致死量（LD10）分别为11．13、9．97、6．82、4．10mmol／L,半致死量（LD50）分别为15．24、12．16、10．94、7．68mmol／L,90％致死量（LD90）分别为19．47、15．88、14．85、11．78mmol／L,全致死量（LD100）分别为20．21、16．64、16．41、13．49mmol／L,安全量（SD）为2．83mmol／L。适宜中华蟾蜍蝌蚪生长发育的水环境中碳酸盐碱度的范围在1．0～3．0mmol／L。[结论]碱度应控制在有利于水生生物种群生长和发育的适宜范围,才能使生物种群数量与环境协调发展。     

Melanopsin (Opn4) requirement for normal light-induced circadian phase shifting

The master circadian oscillator in the hypothalamic suprachiasmatic nucleus is entrained to the day/night cycle by retinal photoreceptors. Melanopsin (Opn4), an opsin-based photopigment, is a primary candidate for photoreceptor-mediated entrainment. To investigate the functional role of melanopsin in light resetting of the oscillator, we generated melanopsin-null mice (Opn4-/-). These mice entrain to a light/dark cycle and do not exhibit any overt defect in circadian activity rhythms under constant darkness. However, they display severely attenuated phase resetting in response to brief pulses of monochromatic light, highlighting the critical role of melanopsin in circadian photoentrainment in mammals.     

Identification of small molecule activators of cryptochrome

Impairment of the circadian clock has been associated with numerous disorders, including metabolic disease. Although small molecules that modulate clock function might offer therapeutic approaches to such diseases, only a few compounds have been identified that selectively target core clock proteins. From an unbiased cell-based circadian phenotypic screen, we identified KL001, a small molecule that specifically interacts with cryptochrome (CRY). KL001 prevented ubiquitin-dependent degradation of CRY, resulting in lengthening of the circadian period. In combination with mathematical modeling, our studies using KL001 revealed that CRY1 and CRY2 share a similar functional role in the period regulation. Furthermore, KL001-mediated CRY stabilization inhibited glucagon-induced gluconeogenesis in primary hepatocytes. KL001 thus provides a tool to study the regulation of CRY-dependent physiology and aid development of clock-based therapeutics of diabetes.     

Transplanted suprachiasmatic nucleus determines circadian period

The pacemaker role of the suprachiasmatic nucleus in a mammalian circadian system was tested by neural transplantation by using a mutant strain of hamster that shows a short circadian period. Small neural grafts from the suprachiasmatic region restored circadian rhythms to arrhythmic animals whose own nucleus had been ablated. The restored rhythms always exhibited the period of the donor genotype regardless of the direction of the transplant or genotype of the host. The basic period of the overt circadian rhythm therefore is determined by cells of the suprachiasmatic region.     

光照周期对尼罗罗非鱼幼鱼昼夜节律调节的作用

为了研究尼罗罗非鱼幼鱼游泳行为在不喂食时是否存在昼夜节律和光照周期的调节作用,设计了光周期为光照(L)∶黑暗(D)=12 h∶12 h,持续的黑暗(DD),持续的光照(LL),光周期为L∶D=6 h∶6 h和光周期为L∶D=2 h∶2 h。结果表明:(1)光周期为L∶D=12 h∶12 h时,尼罗罗非鱼具有明显的昼夜节律,昼夜节律周期为(24. 3±0. 2) h;(2)尼罗罗非鱼的昼夜节律在持续的黑暗和光照下仍然存在,分别为(25. 1±1. 1) h和(25. 6±1. 0) h;(3)光周期为L∶D=6 h∶6 h时,尼罗罗非鱼仍具有明显的昼夜节律(12. 6±0. 5) h;(4)在光周期为L∶D=2 h∶2 h时,尼罗罗非鱼的昼夜游泳行为仍具有明显的昼夜节律,节律周期为(4. 0±2. 0) h。这些结果表明,尼罗罗非鱼具有以24 h为周期的内源性生物钟,但相比与外源性光照调控,内源性的生物钟对罗非鱼的调控较弱,外源性的光照周期才是调节尼罗罗非鱼幼鱼昼夜行为节律的主要因素。     

亚硝基胍对链格孢菌LD2-13的诱变改造

为了获得对小蓟致病力强的生防菌株,采用亚硝基胍对出发菌株LD2-13进行化学诱变。筛选出突变株LD2-13-4,其菌丝生长速率、分生孢子产量以及对小蓟的致病力较野生菌株LD2和出发菌株LD2-13均有明显的提高,可作为小蓟生物防治的潜力菌株。     

Circadian rhythms of liver enzymes and their relationship to enzyme induction

Tyrosine alpha ketoglutarate transaminase, which is rapidly induced by various agents, shows circadian rhythmicity in the intact rat. This rhythmicity is only slightly altered after adrenalectomy, indicating that adrenal hormones do not play a major role in the metabolic control of the activity of tyrosine alpha ketoglutarate transaminase. On the other hand, phenylalaninepyruvate transaminase, which is not inducible over the same time period, does not show circadian variation. The results suggest that the sensitivity of an enzyme's regulating system to inducing agents may be related to the inherent circadian rhythm of the enzyme.     

CikA, a bacteriophytochrome that resets the cyanobacterial circadian clock

The circadian oscillator of the cyanobacterium Synechococcus elongatus, like those in eukaryotes, is entrained by environmental cues. Inactivation of the gene cikA (circadian input kinase) shortens the circadian period of gene expression rhythms in S. elongatus by approximately 2 hours, changes the phasing of a subset of rhythms, and nearly abolishes resetting of phase by a pulse of darkness. The CikA protein sequence reveals that it is a divergent bacteriophytochrome with characteristic histidine protein kinase motifs and a cryptic response regulator motif. CikA is likely a key component of a pathway that provides environmental input to the circadian oscillator in S. elongatus.     

The Neurospora checkpoint kinase 2: a regulatory link between the circadian and cell cycles

The clock gene period-4 (prd-4) in Neurospora was identified by a single allele displaying shortened circadian period and altered temperature compensation. Positional cloning followed by functional tests show that PRD-4 is an ortholog of mammalian checkpoint kinase 2 (Chk2). Expression of prd-4 is regulated by the circadian clock and, reciprocally, PRD-4 physically interacts with the clock component FRQ, promoting its phosphorylation. DNA-damaging agents can reset the clock in a manner that depends on time of day, and this resetting is dependent on PRD-4. Thus, prd-4, the Neurospora Chk2, identifies a molecular link that feeds back conditionally from circadian output to input and the cell cycle.     

Control mechanism of the circadian clock for timing of cell division in vivo

Cell division in many mammalian tissues is associated with specific times of day, but just how the circadian clock controls this timing has not been clear. Here, we show in the regenerating liver (of mice) that the circadian clock controls the expression of cell cycle-related genes that in turn modulate the expression of active Cyclin B1-Cdc2 kinase, a key regulator of mitosis. Among these genes, expression of wee1 was directly regulated by the molecular components of the circadian clockwork. In contrast, the circadian clockwork oscillated independently of the cell cycle in single cells. Thus, the intracellular circadian clockwork can control the cell-division cycle directly and unidirectionally in proliferating cells.     

Characterization of Ppd-D1 alleles on the developmental traits and rhythmic expression of photoperiod genes in common wheat

Photoperiodic response is an important characteristic that plays an important role in plant adaptability for various environments. Wheat cultivars grow widely and have high yield potential for the strong photoperiod adaptibility. To assess the photoperiodic response of different genotypes in wheat cultivars, the photoperiodic effects of the Ppd-D1 alleles and the expressions of the related TaGI, TaCO and Ta FT genes in Liaochun 10 and Ningchun 36 were investigated under the short-day(6 h light, SD), moderate-day(12 h light, MD) and long-day(24 h light, LD) conditions. Amplicon length comparison indicated that the promoter of Ppd-D1 in Ningchun 36 is intact, while Liaochun 10 presented the partial sequence deletion of Ppd-D1 promoter. The durations of all developmental stages of the two cultivars were reduced by subjection to an extended photoperiod, except for the stamen and pistil differentiation stage in the Liaochun 10 cultivar. The expression levels of the Ppd-D1 alleles and the TaGI, TaCO and TaFT genes associated with the photoperiod pathway were examined over a 24-h period under SD and MD conditions. The relationships of different photoperiodic responses of the two cultivars and the expression of photoperiod pathway genes were analyzed accordingly. The photoperiod insensitive(PI) genotype plants flower early under SD; meanwhile, the abnormal expression of the Ppd-D1 a allele is accompanied with an increase in Ta FT1 expression and the TaCO expression variation. The results would facilitate molecular breeding in wheat.     

长日照条件下2个热带玉米自交系的转录组差异分析

【目的】深度挖掘不同光敏类型自交系间的差异表达基因,为揭示热带玉米种质光周期敏感性变异机理提供理论依据,同时为采用分子辅助方法改良热带玉米种质提供新途径。【方法】以热带光钝感自交系QR273和光敏感自交系T32为试验材料,通过人工控制长日照条件（16 h光/8 h暗）对试验材料进行处理,于四叶期采集幼嫩叶片提取总RNA,利用RNA-Seq技术对不同光敏类型自交系材料进行转录组测序,同时结合生物信息学分析,筛选出不同光敏类型自交系间的差异表达基因。【结果】在长日照条件下,从玉米自交系T32和QR273间共鉴定出6977个差异表达基因,其中T32较QR273的上调表达基因有3291个、下调表达基因有3686个。GO功能注释分析结果显示,有24个应答光刺激和应答辐射的基因在T32和QR273中表现出显著差异;此外,有17个同时与应答光刺激、应答辐射、胚后期发育、光周期、生殖结构发育、生殖系统发育、生殖发育过程、光周期/开花和分生组织营养生长向生殖生长转变相关的差异表达基因。KEGG信号通路富集分析发现有15个昼夜节律通路相关基因在T32和QR273中表现出显著差异,其中,Zm00001e030377和Zm00001e023792基因在T32中的表达量高于QR273,而Zm00001e016746和Zm00001e011193基因在T32中的表达量低于QR273。【结论】长日照条件下光敏型与光钝型热带玉米自交系间的转录组差异分析共鉴定出6977个显著差异表达基因,包括24个参与应答光刺激和应答辐射的差异表达基因有,17个同时与应答光刺激、应答辐射、胚后期发育、光周期及分生组织营养生长向生殖生长转变相关的差异表达基因,以及15个与昼夜节律通路相关的差异表达基因。这些基因通过差异性参与昼夜节律通路中的成花诱导,导致成花启动途径不完全相同,可能是热带种质光周期敏感性变异的关键遗传基因。