A New C-Glycosylflavone from the Leaves of Cycas panzhihuaensis

A new C-glycosylflavone, named panzhihuacycaside (1), was isolated from the leaves of Cycas panzhihuaensis L. Zhou et S. Y. Yang (Cycadaceae) along with 2,3-dihydrohinokiflavone (2), 5,5',7,7', 4',4''-hexahydroxy-(2',8')-biflavone (3), vanillic acid (4), P-sitosterol (5) and daucosterol (6). Their structures were elucidated by spectral and chemical evidence.

堆芯核设计程序CYCAS少群截面模型开发

少群截面模型为堆芯三维扩散计算提供实时的节块均匀少群截面,是堆芯计算程序的关键模型之一。CYCAS程序是上海核工程研究设计院最新开发的堆芯三维核设计程序。本文在详细解析影响节块截面的各种因素的基础上,提出应用于CYCAS程序的少群截面的模型。该模型采用能谱修正方法处理由于能谱变化所引入的二次效应,采用微观燃耗修正方法处理燃耗历史效应。单组件和AP1000核电厂的数值验证计算表明,该模型具有很高的计算精度。

堆芯核设计程序CYCAS动力学模型开发

对堆芯核设计程序CYCAS的动力学模型及其数值验证进行了研究。详细介绍了CYCAS程序采用的动力学模型。为验证模型的有效性,对LMW瞬态基准题和基于AP1000堆芯动态插棒问题进行了数值模拟和分析。结果表明,CYCAS程序的动力学模型可获得可靠的计算结果。

四川苏铁(Cycas szechuanensis)营养器官的解剖结构研究

对四川苏铁（Cycas szechuanensis Cheng et L.K Fu）根、茎、叶的解剖结构进行了研究.结果表明,根初生结构由表皮、皮层和中柱3部分组成,未见明显的中柱鞘和内皮层,具二原型木质部,皮层薄壁细胞中含有大量的晶体;茎具大量薄壁组织,薄壁组织中有明显的分泌腔,薄壁细胞富含淀粉粒,维管束呈环形排列或散布在薄壁组织中;叶柄的基本组织中具有裂生分泌腔,5～8束维管束呈弧形排列或散布在薄壁组织中;羽片叶上表皮的角质层厚,气孔分布在下表皮,有小叶脉产生.根、茎、叶木质部中的管胞主要是螺纹和孔纹管胞,有少量纤维.

Genetic characterization of the entire range of Cycas panzhihuaensis (Cycadaceae)

Cycas panzhihuaensis L.Zhou & S.Y.Yang(Cycadaceae) is an endangered gymnosperm species endemic to the dry-hot valley of the Jinsha River basin in southwest China.Although the wild C.panzhihuaensis population from Panzhihua Cycad Natural Reserve is well protected and its genetic diversity has been well assessed,the genetic characteristics of populations outside the nature reserve,which face larger risks of extinction,remain unknown.Furthermore,the population genetics and historical dynamics of this endemic and endangered species have not been examined across its entire range.In this study,to analyze the genetic diversity,phylogeographical structure and demographic history of C.panzhihuaensis from all its seven known locations,we sequenced and compared molecular data from chloroplastic DNA(psbA-trnH,psbM-trnD,and trnS-trnG),single-copy nuclear genes(PHYP,AC5,HSP70,and AAT) from 61 individuals,as well as 11 nuclear micro satellite loci(SSR) from 102 individuals.We found relatively high genetic diversity within populations and high genetic differentiation among populations of C.panzhihuaensis,which is consistent with the patterns of other Asian inland cycads.Although no significant phylogeographical structure was detected,we found that small and unprotected populations possess higher genetic diversity and more unique haplotypes,which revises our understanding of diversity within this species and deserves due attention.Analysis of demographic dynamics suggest that human activity might be the key threat to C.panzhihuaensis.Based on the genetic characterization of C.panzhihuaensis,we propose several practical guidelines for the conservation of this species,especially for the populations with small sizes.

Extract of Cycas revoluta Thunb. enhances the inhibitory effect of 5-fluorouracil on gastric cancer cells through the AKT-mTOR pathway

BACKGROUND Gastric cancer is one of the most common and deadly malignancies worldwide.Despite recent medical progress, the 5-year survival rate of gastric cancer is still unsatisfactory. 5-fluorouracil(5-Fu) is one of the first-line antineoplastic treatments for gastric cancer, as it can effectively induce cancer cell apoptosis.However, the effect of 5-Fu is limited due to drug resistance of the malignant tumor. Previous studies have reported that Sotetsuflavone from Cycas revoluta Thunb. can markedly suppress lung cancer cell proliferation by apoptosis,though its effect on gastric cancer remains unknown.AIM To investigate the inhibitory effect of Cycas revoluta Thunb. and to determine whether it can overcome gastric cancer cell drug resistance to 5-Fu.METHODS Cell viability was examined to determine whether the natural extract of Cycas revoluta Thunb. induced gastric cancer cell death. The half-maximal effective concentration and the half-maximal lethal concentration were calculatede.Wound-healing and transwell assays were performed to examine gastric cancer cell motility. Clonogenic assays were performed to investigate the synergistic effects of Cycas revoluta Thunb. with 5-Fu, and apoptotic bodies were detected by Hoechst staining. Western blotting was performed to examine the expression of related proteins and to investigate the molecular mechanism of Cycas revoluta Thunb.-induced cancer cell apoptosis. The expressions of proteins, including mammalian target of rapamycin(mTOR) and p-AKT, were detected in different combinations of treatments for 48 h, then analyzed by ECL detection.RESULTS Gastric cancer cells were more sensitive to the natural extract of Cycas revoluta Thunb. compared to normal gastric epithelial cells, and the extract effectively inhibited gastric cancer cell migration and invasion. The extract improved the anti-cancer effect of 5-Fu by enhancing the chemosensitization of gastric cancer cells. Extract plus 5-Fu further reduced the expression of the drug-resistancerelated proteins p-AKT and mTOR after 48 h compared to 5-Fu alone. Compared to 5-Fu treatment alone, mTOR and p-AKT expression was significantly reduced by about 50% and 75%, respectively. We also found that the natural extract of Cycas revoluta Thunb. further increased 5-Fu-induced gastric cancer cell apoptosis. Expression of apoptosis-related protein X-linked inhibitor of apoptosis protein and apoptosis inducing factor were significantly reduced and increased,respectively, in the 5-Fu-resistant gastric cancer line SGC-7901/R treated with extract plus 5-Fu, while the expression of survivin did not change.CONCLUSION The natural extract of Cycas revoluta Thunb. effectively inhibited gastric cancer cell growth and enhanced the anti-cancer effect of 5-Fu through the AKT-mTOR pathway.

Genetic structure and demographic history of Cycas chenii(Cycadaceae),an endangered species with extremely small populations

Geological activities and climate oscillations during the Quaternary period profoundly impacted the distribution of species in Southwest China. Some plant species may be harbored in refugia, such as the dry-hot valleys of Southwest China. Cycas chenii X. Gong & W. Zhou, a critically endangered cycad species, which grows under the canopy in subtropical evergreen broad-leaved forests along the upstream drainage area of the Red River, is endemic to this refugium. In this study, 60 individuals of C. chenii collected from six populations were analyzed by sequencing two chloroplast intergenic spacers(cp DNA:psb A-trn H and trn L-trn F) and two nuclear genes(PHYP and RBP-1). Results showed high genetic diversity at the species level, but low within-population genetic diversity and high interpopulation genetic differentiation. A Bayesian phylogenetic tree based on cp DNA showed that five chloroplast haplotypes were clustered into two clades, which corresponds to the division of the western and eastern bank of the Red River. These data indicate a possible role for the Red River as a geographic barrier to gene flow in C. chenii.Based on our findings, we propose appropriate in situ and ex situ conservation strategies for C. chenii.

Mechanical Pressure, Not Genes, Makes Ovulate Parts Leaf-Like in <i>Cycas</i>

The so-called “megasporophylls” of Ginkgoales, Coniferales, and Gnetales have been proven metamorphosed shoots, making “megasporophyll” of Cycas the last one resembling a leaf. Why and how it is so in Cycas (the most ancient seed plant dated back to the Palaeozoic) become key questions because their answers are hinged with the fates of several hypotheses in botany. Here, we performed a controlled developmental experiment on the ovulate parts (megasporophylls) in a single strobilus of Cycas sexseminifera. By removing the neighboring ones, two of the ovulate parts were left isolated spatially from others, in contrast to others left intact. A half-year-long continuous observation indicates that the isolated ovulate parts change their ovule arrangement from initial pinnate into helical pattern, while the intact ones in the same strobilus remain pinnate as usual. Since all ovulate parts are in the same strobilus and controlled by the same genome in this case and the only difference is lack of pressure from neighbors for the isolated ones, the changes in ovule orientation and ovulate part morphology can only be attributed to the lack of mechanical pressure among the ovulate parts. Therefore, we conclude that mechanical pressure, not genes, controls the morphology of ovulate parts and contributes to the leaf-like ovulate part morphology in Cycas. This conclusion cautions previous superficial interpretations of plant morphology.

Generation and characterization of expressed sequence tags(ESTs) from coralloid root cDNA library of Cycas debaoensis

A normalized full-length cDNA library was constructed from the coralloid roots of Cycas debaoensis by the DSN （duplex-specific nuclease） normalization method combined with the SMART （Switching Mechanism At 5＇ end of the RNA Transcript） technique. The titer of the original cDNA library was about 1.5 × 10^6 cfu·mL^-1 and the average insertion size was about 1 kb with a high recombination rate （97%）. The 5011 high-quality expressed sequence tags （ESTs） were obtained from 5393 randomly picked cDNA clones. Clustering and assembly of ESTs resulted in 2984 unique sequences, consisting of 618 contigs and 2366 singlets. EST sequence annotation revealed that 2333 and 1901 unigenes were functionally anno- tated in the NCBI non-redundant database and Swiss-Prot protein database, respectively. Functional analysis demonstrated that 1495 （50.1%） unigenes were associated with 4082 Gene Ontology （GO） terms. A total of 847 unigenes were grouped into 22 Cluster of Orthologous Groups （COG） functional categories. Based on the EST dataset, 22 ESTs that encoded putative receptor-like protein kinase （RLK） genes were screened. Furthermore, a total of 94 simple sequence repeats （SSRs） were discovered, of which 20 loci were successfully amplified in C debaoensis. This study is the first EST analysis for the coralloid roots of C debaoensis and provides a valuable genomic resource for novel gene discovery, gene expression and comparative genomics, conservation and management studies as well as applications in C debaoensis and related cycad species.

德保苏铁幼苗和成年植株的光合特性

通过研究德保苏铁(Cycas debaoensis)幼苗和成年植株的光合特性,为其种质资源保育及引种栽培提供理论依据。以德保苏铁幼苗和成年植株为材料,用Li-6400型便携式光合仪器测定其叶片的净光合速率、气孔导度、蒸腾速率等光合生理指标,并绘制在一定的光照辐射强度梯度下的光响应曲线。结果表明,德保苏铁在不同时期对强光和弱光都有较高的利用能力;德保苏铁在幼苗阶段对弱光有更强的转化利用能力。日变化中,幼苗净光合速率与气孔导度、胞间CO_(2)浓度、蒸腾速率呈负相关,与光强呈正相关;成年植株净光合速率与气孔导度、蒸腾速率、光强呈负相关,与胞间CO_(2)浓度呈正相关。

RNA Editing Sites Exist in Protein-coding Genes in the Chloroplast Genome of Cycas taitungensis

RNA editing is a post-transcriptional process that results in modifications of ribonucleotides at specific locations. In land plants editing can occur in both mitochondria and chloroplasts and most commonly involves C-to-U changes, especially in seed plants. Using prediction and experimental determination, we investigated RNA editing in 40 protein-coding genes from the chloroplast genome of Cycas taitungensis. A total of 85 editing sites were identified in 25 transcripts. Comparison analysis of the published editotypes of these 25 transcripts in eight species showed that RNA editing events gradually disappear during plant evolution. The editing in the first and third codon position disappeared quicker than that in the second codon position, ndh genes have the highest editing frequency while serine and proline codons were more frequently edited than the codons of other amino acids. These results imply that retained RNA editing sites have imbalanced distribution in genes and most of them may function by changing protein structure or interaction. Mitochondrion protein-coding genes have three times the editing sites compared with chloroplast genes of Cycas, most likely due to slower evolution speed.

Biological characteristics of wild Cycas fairylakea population in Guangdong Province,China

There are five wild populations of Cycas fairylakea in Guangdong Province,China,three of which are newly found.A study of the biological characteristics of C.fairylakea populations showed that this species had a narrow colonization area within 300 hm^(2),and an island pattern of distribution.Because of the overexploitation,urbanization,environment pollution,plant diseases,and insect pests,the wild populations and individuals of C.fairylakea decreased markedly in the past decades.All five populations have an opposite pyramid age structure,few coning plants,few seed production,and low level of seed germination rate or sterility.In conclusion,C.fairylakea in Guangdong Province was threatened seriously and an urgent need to take effective efforts to protect the plants and habitats in its location sites was required.

中国苏铁旅游资源开发初探

中国苏铁(Cycas revoluta)旅游资源丰富,极具开发价值,但其旅游开发研究尚处于空白。在概述苏铁研究现状的基础上,分析了苏铁旅游资源具有观赏价值大、资源丰富、文化内涵深厚、科学价值与经济价值高等特点,提出了加大资源保护力度、深入挖掘文化内涵、打造生态旅游品牌、进行产业化发展、加大宣传促销力度等开发策略。

深圳梅林仙湖苏铁野生种群遗传多样性ISSR分析

仙湖苏铁Cycas fairylakeaD.Y.W ang是国家濒危保护植物,目前仅在我国广东省深圳市和曲江县发现有自然分布,个体总数已不足2 000株。本文应用ISSR标记对深圳梅林郊野公园仙湖苏铁野生种群的遗传多样性进行了研究。从100个引物中筛选出10个用于正式扩增,在14个个体中共检测到77个清晰的扩增位点,其中多态性位点67个,多态位点百分率为87.01%。根据所得数据求出的观察等位基因数为1.870 1,有效等位基因数为1.356 8,Ne i基因多样性指数为0.219 6,Shannon多样性指数为0.344 5。与其他苏铁类植物和濒危植物相比,仙湖苏铁仍然保持很高的遗传多样性水平。基于Jaccard相似性系数的UPGMA树系图表明,梅林郊野公园的仙湖苏铁个体明显地分为2个亚群,ISSR表型特征的主成分分析(PCA)也支持了聚类分析结果。研究结果对仙湖苏铁的保育和管理具有重要意义。

新的NS配体CYCA的合成、^(99m)Tc标记及动物分布的研究

为了探索结构与生物分布性质的关系，合成了一种新的ＮＳ配体Ｌ－半胱氨酸酞－对氯苯胺盐酸盐（ＣＹＣＡ）．以ＳｎＣｌ２为还原剂，制备了放化纯大于９３％的９９ｍＴｃＯ－ＣＹＣＡ．探讨了ｐＨ值和反应温度对９９ｍＴｃＯ—ＣＹＣＡ标记率的影响，并对其小鼠生物分布进行了研究．结果表明，９９ｍＴｃｄ－ＣＹＣＡ在脑和心肌中具有一定的浓集，在肝脏中有较高浓集，并且清除速度较慢．这些结果对于探索结构与生物分布性质的关系提供了参考．

Observation on Behavior of Chilades pandava

Chilades pandava is a dangerous insect pest of Cycas spp.,which seriously threatens the growth and development of Cycas plants.On the basis of previous studies,the paper summarized the behaviors of different insect states of C.pandava,such as feeding,flying,resting,mating,spawning,hatching,pupation,eclosion,etc.,in order to provide a reference for effective prevention and control of C.pandava.

极小种群野生植物十万大山苏铁SSR和ISSR反应体系建立及引物筛选

为筛选出适用于极小种群野生植物十万大山苏铁的SSR引物和ISSR引物,建立十万大山苏铁的SSR-PCR和ISSR-PCR反应体系,本研究以十万大山苏铁为试验材料,用改良CTAB法提取其基因组DNA,采用L_(16)(4^(3))正交设计方法,探索2×Taq Mix、引物浓度和模板DNA含量3个指标参数对十万大山苏铁SSR-PCR和ISSR-PCR反应体系的影响。建立了相关优化体系:20μL的SSR-PCR扩增体系中2×Taq Mix10μL、引物0.4μmol/L、模板DNA 25 ng;20μL的ISSR-PCR扩增体系中含2×Taq Mix 10μL、引物0.5μmol/L、模板DNA 60 ng。结果表明,建立的反应体系及筛选出来的15对SSR引物和9条ISSR引物通过了21份十万大山苏铁样品验证,反应体系稳定可靠。

极小种群野生植物十万大山苏铁幼苗的光合生理特性

十万大山苏铁(Cycas shiwandashanica)属于苏铁科(Cycadaceae)苏铁属(Cycas)植物,因其生境破碎,野生资源稀少,被列为极小种群。目前缺乏对其野生资源的群落结构调查与栽培研究。本研究以十万大山苏铁幼苗为研究对象,测定其一年生、二年生幼苗的生长指标,并采用Li-6400便携式光合仪测定一年生幼苗的光合日变化和光合响应曲线。结果表明,十万大山苏铁一年生幼苗与二年生幼苗的苗高、地径和冠幅显著增加,生长良好。十万大山苏铁净光合速率Pn日变化为双峰曲线,两个峰值出现在上午10:30和下午14:30,净光合速率分别为1.73μmol•m^(-2)•s^(-1)和1.76μmol•m^(-2)•s^(-1),没有出现光合午休现象,净光合速率受到气孔因素和非气孔因素限制。十万大山苏铁的光补偿点(LCP)为3.68μmol•m^(-2)•s^(-1)、光饱和点(LSP)为1023.67μmol•m^(-2)•s^(-1),最大光合速率(Pmax)为3.57μmol•m^(-2)•s^(-1),属于中生植物。本研究通过测定十万大山苏铁的生长势和光合特性,首次揭示了该植物的光合生理特性,为十万大山苏铁的保护及引种栽培提供技术支撑和缓解十万大山苏铁的濒危状态提供理论支持,对十万大山苏铁的保护研究具有理论价值和指导意义。

OCCURRENCE OF EARLIEST CYCADS IN THE PERMIAN OF CHINA AND ITS BEARING ON THEIR EVOLUTION

Living cycads show a range of archaic features which suggest that they are primitive plants. They have a long fossil record, but this unfortunately consists largely of vegetative leaves. Very few reproductive organs are preserved as fossils. However,

ERF4 interacts with and antagonizes TCP15 in regulating endoreduplication and cell growth in Arabidopsis

Endoreduplication is prevalent during plant growth and development,and is often correlated with large cell and organ size.Despite its prevalence,the transcriptional regulatory mechanisms underlying the transition from mitotic cell division to endoreduplication remain elusive.Here,we characterize ETHYLENE-RESPONSIVEELEMENTBINDING FACTOR 4(ERF4)as a positive regulator of endoreduplication through its function as a transcriptional repressor.ERF4 was specifically expressed in mature tissues in which the cells were undergoing expansion,but was rarely expressed in young organs.Plants overexpressing ERF4 exhibited much larger cells and organs,while plants that lacked functional ERF4 displayed smaller organs than the wild-type.ERF4 was further shown to regulate cell size by controlling the endopolyploidy level in the nuclei.Moreover,ERF4 physically associates with the class I TEOSINTE BRANCHED 1/CYCLOIDEA/PCF(TCP)protein TCP15,a transcription factor that inhibits endoreduplication by activating the expression of a key cell-cycle gene,CYCLIN A2;3(CYCA2;3).A molecular and genetic analysis revealed that ERF4promotes endoreduplication by directly suppressing the expression of CYCA2;3.Together,this study demonstrates that ERF4 and TCP15 function as a module to antagonistically regulate each other?s activity in regulating downstream genes,thereby controlling the switch from the mitotic cell cycle to endoreduplication during leaf development.These findings expand our understanding of how the control of the cell cycle is fine-tuned by an ERF4–TCP15 transcriptional complex.