Activation of gibberellin 2-oxidase 6 decreases active gibberellin levels and creates a dominant semi-dwarf phenotype in rice （Oryza sativa L.）

Gibberellin (GA) 2-oxidase plays a key role in the GA catabolic pathway through 2β-hydroxylation.In the present study,we isolated a CaMV 35S-enhancer activation tagged mutant,H032.This mutant exhibited a dominant dwarf and GA-deficient phenotype,with a final stature that was less than half of its wild-type counterpart.The endogenous bioactive GAs are markedly decreased in the H032 mutant,and application of bioactive GAs (GA3 or GA4) can reverse the dwarf phenotype.The integrated T-DNA was detected 12.8 kb upstream of the OsGA2ox6 in the H032 genome by TAIL-PCR.An increased level of OsGA2ox6 mRNA was detected at a high level in the H032 mutant,which might be due to the enhancer role of the CaMV 35S promoter.RNAi and ectopic expression analysis of OsGA2ox6 indicated that the dwarf trait and the decreased levels of bioactive GAs in the H032 mutant were a result of the up-regulation of the OsGA2ox6 gene.BLASTP analysis revealed that OsGA2ox6 belongs to the class III of GA 2-oxidases,which is a novel type of GA2ox that uses C20-GAs (GA12 and/or GA53) as the substrates.Interestingly,we found that a GA biosynthesis inhibitor,paclobutrazol,positively regulated the OsGA2ox6 gene.Unlike the over-expression of OsGA2ox1,which led to a high rate of seed abortion,the H032 mutant retained normal flowering and seed production.These results indicate that OsGA2ox6 mainly affects plant stature,and the dominant dwarf trait of the H032 mutant can be used as an efficient dwarf resource in rice breeding.     

Axial nature of the cupule‐bearing organ in Caytoniales

Abstract Caytoniales are an important group of seed plants, and the nature of their female reproductive organ may influence interpretations of the seed plant phylogeny and the origin of angiosperms. Although not convincingly demonstrated by clear evidence, cupules on previously described specimens were interpreted as being distichously arranged, implying that the cupule‐bearing organ in Caytoniales was a pinnate megasporophyll. Here a female reproductive organ of Paracaytonia hongtaoi gen. et sp. nov. (Caytoniales) is reported from Liaoning, China. The well preserved specimen clearly shows a spiral arrangement of cupules along the reproductive axis, suggesting that the cupule‐bearing organ in Caytoniales is not a megasporophyll but a branch. This new information on the axial nature of the cupule‐bearing organ in Caytoniales has significant implications on the placement of Caytoniales in the seed plant phylogeny and interpretation of the relationship between Caytoniales and angiosperms.     

不同植物LDOX/ANS基因的生物信息学分析

花青素是一类重要的植物次生代谢产物。本文采用生物信息学的方法对已在GenBank上登录的拟南芥、西洋梨、苹果、桃、葡萄、芥菜、菊花新品种和水稻等植物的无色花青素双加氧酶/花青素合成酶(LDOX/ANS)基因的核酸及氨基酸序列、组成成分、导肽、信号肽、跨膜结构域、疏水性/亲水性、蛋白质二级结构、三级结构及功能域等进行预测和推断。结果表明,ORF除了桃和菊花新品种为500bp左右之外,其它几种植物都在1070bp左右,分子量均为4kD左右,理论等电点均低于7,说明LDOX/ANS呈酸性。Glu、Leu和Val是这些植物共有的主要氨基酸。核苷酸同源性比对结果显示,拟南芥LDOX/ANS与其它植物LDOX/ANS的同源性较高;8个物种的LDOX/ANS基因被分为两个大类,单子叶植物水稻LDOX/ANS基因被单独分为一类,其它的均聚成一大类。研究还发现这些植物的LDOX/ANSN端不存在导肽和信号肽,无跨膜结构域,肽链表现为亲水性。蛋白质二级结构中最主要的结构元件是α-螺旋和无规则卷曲,包含一个20G-FeⅡOxy功能结构域。通过此次研究,希望为今后深入研究该类酶的功能和结构特征提供依据。     

紫外诱变筛选海洋红酵母S8的尿嘧啶缺陷型菌株

本课题组从海南天然海域筛选到一株高产类胡萝卜素的海洋红酵母菌株S8,该菌株对鱼无毒害,并与鱼共生,欲将其应用于盐诱导表达外源蛋白的海洋红酵母工程菌的构建。本研究利用紫外诱变筛选的方法处理S8菌株,通过统计其UV致死率、5-氟乳清酸致死率等筛选S8的尿嘧啶营养缺陷型突变株。研究结果表明,供试菌株通过紫外线诱变、5-氟乳清酸致死和回复突变率的实验筛选,共获得16株稳定的尿嘧啶缺陷型突变株,突变菌株在基本培养基中培养了8d仍不能生长。选择了其中的一株ST5进行了产胡萝卜素能力的测定,结果表明,在同样的培养条件下,野生型S8菌株细胞生物产量可达87.55g/L,类胡萝卜素含量可达520μg/g,突变株ST5的细胞生物产量为85.45g/L,类胡萝卜素含量为512μg/g;ST5的产胡萝卜素能力方面与野生型S8无明显差异。因此,尿嘧啶缺陷型菌株ST5可为下一步海洋红酵母工程菌的构建提供受体菌。     

毛薯ISSR-PCR反应体系的建立

本研究主要建立毛薯ISSR-PCR的最佳反应体系。研究采用改良CTAB法提取毛薯总基因组DNA,应用单因子实验法设定模板DNA,Mg2+浓度,dNTP浓度,Tap酶浓度以及退火温度的5个不同梯度,探讨单因素变化对毛薯ISSR-PCR扩增的影响。实验结果表明,毛薯ISSR-PCR最佳反应体系为:总体积20μL,模板DNA为50ng、Taq酶为0.8U、Mg2+浓度为2.0mmol/L、引物浓度为0.5μmol/L、dNTPs浓度为0.5mmol/L。     

植物硫氧还蛋白系统

硫氧还蛋白是一类催化二硫键氧化还原的小蛋白,它通过调控细胞中氧化还原状态发挥重要的作用。在植物中,硫氧还蛋白系统尤为复杂,参与了植物的新陈代谢、转录翻译调控、信号传导以及植物的抗逆反应等。本文主要通过对植物硫氧还蛋白分类、活性位点、结构以及3种硫氧还蛋白系统研究现状进行概述,并对植物的硫氧还蛋白及系统进行了展望,从而较为全面地综述了植物的硫氧还蛋白系统,为进一步了解硫氧还蛋白在植物体内的作用机制奠定基础,也为今后的相关研究提供参考。     

Molecular genetics of Brugada syndrome

Brugada syndrome (BrS) is a life-threatening cardiac rhythm disorder characterized by persistent STsegment elevation in leads V1–V3 and right bundle branch block on electrocardiograms (ECG), and by syncope and sudden death from ventricular tachycardia (VT) and ventricular fibrillation (VF). BrS is responsible for nearly 4% of sudden cardiac deaths and considered to be the most common cause of natural death in males younger than 50 years in some Asian countries. Since the first diseasecausing gene for BrS (the cardiac sodium channel gene SCN5A) was identified in 1998, extensive investigations on both clinical and basic aspects of BrS have occurred rapidly. SCN5A mutations remain the most common cause of BrS; nearly 300 SCN5A mutations have been identified and are responsible for 20%–30% of BrS cases. Commercial genetic testing is available for SCN5A. Recently, seven other disease-causing genes for BrS have been identified and include GPD1L (BrS2), CACNA1C (Cav1.2, BrS3), CACNB2 (Cavβ2, BrS4), SCN1B (Navβ1, BrS5), KCNE3 (MiRP2, BrS6), SCN3B (Navβ3, BrS7), and HCN4 (BrS8). This article will briefly review the progress made over the past decade in our understanding of the clinical, genetic and molecular aspects of BrS.     

Protective effect of supplemental anthocyanins on Arabidopsis leaves under high light

Ten anthocyanin components have been detected in roots of purple sweet potato (Ipomoea batatas Lam.) by high‐performance liquid chromatography coupled to diode array detection and electrospray ionization tandem mass spectrometry. All the anthocyanins were exclusively cyanidins or peonidin 3‐sophoroside‐5‐glucosides and their acylated derivatives. The total anthocyanin content in purple sweet potato powder obtained by solid‐phase extraction was 66 mg g^?1. A strong capacity of purple sweet potato anthocyanins (PSPA) to scavenge reactive oxygen species (superoxide, hydroxyl radical) and the stable 1,1‐diphenyl‐2‐picrylhydrazyl organic free radical was found in vitro using the electron spin resonance technique. To determine the functional roles of anthocyanins in leaves in vivo, for the first time, supplemental anthocyanins were infiltrated into leaves of Arabidopsis thaliana double mutant of the ecotype Landsberg erecta (tt3tt4) deficient in anthocyanin biosynthesis. Chlorophyll fluorescence imaging showed that anthocyanins significantly ameliorated the inactivation of photosystems II during prolonged high‐light (1300 µmol m^?2 s^?1) exposure. Comet assay of DNA revealed an obvious role of supplemental PSPA in alleviating DNA damage by high light in leaves. Our results suggest that anthocyanins could function in vitro and in vivo to alleviate the direct or indirect oxidative damage of the photosynthetic apparatus and DNA in plants caused by high‐light stress.