A novel cold-tolerant Clostridium strain PXYL1 isolated from a psychrophilic cattle manure digester that secretes thermolabile xylanase and cellulase

A Clostridium strain PXYL1 was isolated from a cold-adapted cattle manure biogas digester at 15 degrees C. It could grow at temperatures as low as 5 degrees C up to 50 degrees C with highest specific growth rate at 20 degrees C and is a psychrotroph. It produced extracellular hydrolytic enzymes namely xylanase, endoglucanase, beta-xylosidase, beta-glucosidase and filter paper cellulase, all of which had maximal activity at 20 degrees C. The induction of xylanase was highest on birch wood xylan (37 IU(mg protein)(-1)) compared with xylose (1.11 IU(mg protein)(-1)), cellobiose (1.43 IU(mg protein)(-1)) and glucose (no activity). The xylanase was thermolabile with a half-life of 30 min at 40 degrees C and 8 min at 50 degrees C but stable for over 2 h at 20 degrees C. The crude enzyme released reducing sugars (1.25 g l(-1)) from finger millet flour at 20 degrees C, while commercial food-grade xylanases showed no hydrolysis at this temperature. This is the first report of a Clostridium strain growing at 20 degrees C and producing an array of xylanolytic and cellulolytic enzymes, possessing low temperature optima of 20 degrees C, which may facilitate degradation of plant fibre under low-temperature conditions.     

谷子β-胡萝卜素异构酶家族基因的表达与变异分析

株型是影响谷类作物产量的重要性状, 株型改良对提高作物产量具有重要意义。独脚金内酯(strigolactones, SLs)作为一种最新被鉴定的植物激素, 其通过抑制腋芽的伸长调控分枝/分蘖的形成。β-胡萝卜素异构酶(D27s)是SLs合成途径的关键酶, 通过对谷子(Setaria italica) β-胡萝卜素异构酶典型结构域Pfam:DUF4033进行分析, 鉴定到3个谷子D27s基因家族成员(Seita.8G168400、Seita.6G088800和Seita.3G050900)。蛋白质特性分析显示, 谷子D27s蛋白由271-277个氨基酸残基组成, 分子量为30.1-30.4 kDa, 等电点为5.85-9.31, 不稳定系数介于38.48-74.47之间, 且均定位于叶绿体; 系统进化分析发现, 谷子D27s家族成员位于3个不同进化分支; 顺式作用元件预测显示, SiD27-1 (Seita.8G168400)可能参与调控生物节律、生长素介导的生长发育以及干旱和低温等胁迫应答过程。基因表达分析显示, SiD27-1在谷子多分蘖材料中表达下调, 在低磷胁迫处理下, D27s基因均能产生不同程度的响应, 并且SiD27-1的响应较其它成员更快速。单倍型分析结果表明, SiD27-1的H001单倍型为优异单倍型, 对谷子的株高、抽穗期和产量改良具有重要应用价值。综上, 推测SiD27-1极可能在SLs合成中发挥关键作用并对谷子株型产生影响。研究结果为深入揭示D27s对谷子分蘖形成的调控机制奠定了基础, 也为谷子株型分子设计育种提供了优异的等位变异位点。     

甘肃省谷子地方品种营养品质的分析与评价

对甘肃省199份谷子地方品种子粒的营养品质分析结果表明:蛋白质和脂肪的平均含量较高,品种间差异大,变异丰富;不同地区谷子品种的营养品质存在差异,陇东地区谷子蛋白质和脂肪含量较高;不同粒色谷子营养品质也存在差异,青色籽粒的谷子其蛋白质、脂肪和赖氨酸含量较高。     

Diverse origins of waxy foxtail millet crops in East and Southeast Asia mediated by multiple transposable element insertions

The naturally occurring waxy and low-amylose variants of foxtail millet and other cereals, like rice and barley, originated in East and Southeast Asia under human selection for sticky foods. Mutations in the GBSS1 gene for granule-bound starch synthase 1 are known to be associated with these traits. We have analyzed the gene in foxtail millet, and found that, in this species, these traits were originated by multiple independent insertions of transposable elements and by subsequent secondary insertions into these elements or deletion of parts of the elements. The structural analysis of transposable elements inserted in the GBSS1 gene revealed that the non-waxy was converted to the low-amylose phenotype once, while shifts from non-waxy to waxy occurred three times, from low amylose to waxy once and from waxy to low amylose once. The present results, and the geographical distribution of different waxy molecular types, strongly suggest that these types originated independently and were dispersed into their current distribution areas. The patterns of GBSS1 variation revealed here suggest that foxtail millet may serve as a key to solving the mystery of the origin of waxy-type cereals in Asia. The GBSS1 gene in foxtail millet provides a new example of the evolution of a gene involved in the processes of domestication and its post-domestication fate under the influence of human selection. Electronic Supplementary Material Supplementary material is available for this article at     

应用RAFD标记研究不同生态区谷子品种的遗传差异

应用RAPD标记对19份国内不同生态区的谷子品种的遗传变异进行了研究。结果表明：分子水平上,不同生态区的谷子品种间存在一定的遗传差异,但遗传差异程度并不高。11个随机引物共扩增出54条多态性带,不同引物扩增的带数差异较大,每个引物可扩增2—8条多态性带,平均每个引物扩增出4．91条多态性带。引物1050扩增的多态性带最多(8条)。聚类结果表明,基于RAPD标记分析的遗传聚类群与生态类型有很大的一致性。     

Destructive and non-destructive measurements of residual crop residue and phosphorus effects on growth and composition of herbaceous fallow species in the Sahel

Little is known about the residual effects of crop residue (CR) and phosphorus (P) application on the fallow vegetation following repeated cultivation of pearl millet [Pennisetum glaucum (L.) R. Br.] in the Sahel. The objective of this study, therefore, was (i) to measure residual effects of CR, mulched at annual rates of 0, 500, 1000 and 2000 kg CR ha^–1, broadcast P at 0 and 13 kg P ha^–1 and P placement at 0, 1, 3, 5 and 7 kg P ha^–1 on the herbaceous dry matter (HDM) 2 years after the end of the experiment and (ii) to test a remote sensing method for the quantitative estimation of HDM. Compared with unmulched plots, a doubling of HDM was measured in plots that had received at least 500 kg CR ha^–1. Previous broadcast P application led to HDM increases of 14% compared with unfertilised control plots, whereas no residual effects of P placement were detected. Crop residue and P treatments caused significant shifts in flora composition. Digital analysis of colour photographs taken of the fallow vegetation and the bare soil revealed that the number of normalised green band pixels averaged per plot was highly correlated with HDM (r = 0.86) and that red band pixels were related to differences in soil surface crusting. Given the traditional use of fallow vegetation as fodder, the results strongly suggest that for the integrated farming systems of the West African Sahel, residual effects of soil amendments on the fallow vegetation should be included in any comprehensive analysis of treatment effects on the agro-pastoral system.     

Genome-wide development of transposable elements-based markers in foxtail millet and construction of an integrated database

Transposable elements (TEs) are major components of plant genome and are reported to play significant roles in functional genome diversity and phenotypic variations. Several TEs are highly polymorphic for insert location in the genome and this facilitates development of TE-based markers for various genotyping purposes. Considering this, a genome-wide analysis was performed in the model plant foxtail millet. A total of 30,706 TEs were identified and classified as DNA transposons (24,386), full-length Copia type (1,038), partial or solo Copia type (10,118), full-length Gypsy type (1,570), partial or solo Gypsy type (23,293) and Long- and Short-Interspersed Nuclear Elements (3,659 and 53, respectively). Further, 20,278 TE-based markers were developed, namely Retrotransposon-Based Insertion Polymorphisms (4,801, ∼24%), Inter-Retrotransposon Amplified Polymorphisms (3,239, ∼16%), Repeat Junction Markers (4,451, ∼22%), Repeat Junction-Junction Markers (329, ∼2%), Insertion-Site-Based Polymorphisms (7,401, ∼36%) and Retrotransposon-Microsatellite Amplified Polymorphisms (57, 0.2%). A total of 134 Repeat Junction Markers were screened in 96 accessions of Setaria italica and 3 wild Setaria accessions of which 30 showed polymorphism. Moreover, an open access database for these developed resources was constructed (Foxtail millet Transposable Elements-based Marker Database; http://59.163.192.83/ltrdb/index.html). Taken together, this study would serve as a valuable resource for large-scale genotyping applications in foxtail millet and related grass species.     

3种禾草苗期生长和水分利用对土壤水分变化的反应

采用5种不同的水分处理,于室内生长箱内盆栽条件下对引种禾草柳枝稷(Panicum virgatum)、乡土禾草白羊草(Bothriochloa ischaemum)和栽培禾草谷子(Setaria italica)等苗期根冠生长和水分利用特征进行了比较分析.结果显示:(1)充分供水下3种禾草的苗期生物量和蒸腾效率均显著高于其它4种水分处理,而高水与低水处理下各自的根冠比无显著差异;(2)各水分处理下谷子苗期总生物量、蒸腾效率和耗水量均显著大于白羊草和柳枝稷;(3)在5种水分处理下,苗期根冠比谷子均最小,柳枝稷最大;(4)低降复水后,3种禾草生物量和蒸腾效率较低水处理分别显著提高16.7%-98.7%和28.2%-118.2%,显示出补偿效应,以白羊草增幅最大.结果表明,白羊草、谷子和柳枝稷在不同土壤水分处理下的苗期生物量、根冠分配比例以及水分利用效率差异反映了野生种、栽培种和引进种禾草苗期对半干旱环境条件水分生态适应性的异同.     

根癌农杆菌介导转化谷子的影响因素

利用GUS报告基因,建立了农杆菌介导的谷子(Setaria italica)遗传转化体系,并研究了多种影响因素对转化效率的影响,包括受体基因型、外植体类型、菌液浓度、培养基中乙酰丁香酮的浓度、侵染时间和共培养时间.确定了最优的转化条件为:以谷子幼穗诱导的愈伤组织为外植体,用低浓度的农杆菌菌液侵染30～40min,然后在含有0.1mmol/L乙酰丁香酮的LS培养基上共培养2d.     

糜子育成品种苗期抗旱性评价与鉴定指标筛选

在年降雨量不足40 mm的敦煌市,对我国不同地区育成的56份糜子品种,采用反复干旱法进行了苗期抗旱性鉴定,利用反复干旱存活率和抗旱性综合评价值D的聚类结果筛选出一级抗旱品种4份,分别是陇糜5号、吉3、蒙粳糜1号和蒙粳糜7号;配对t测验显示:反复干旱胁迫后糜子苗高、植株含水量、单株叶面积、生物学产量分别降低了16.097 cm、0.393 g/株、10.358 cm2/株、0.075 g/株,差异达到了极显著水平,而根长、相对生长率反向增加了0.555 cm、3.213%;主成分分析中,植株含水量、生物学产量、单株叶面积3个指标在第1主成分中起决定作用(系数均≥0.881),且与两种抗旱评价参数值相关性均达到了极显著水平,因此,确定植株含水量、生物学产量、单株叶面积作为糜子苗期抗旱性鉴定1级指标。