The hyperthermophilic euryarchaeota Pyrococcus abyssi likely requires the two DNA polymerases D and B for DNA replication

DNA polymerases carry out DNA synthesis during DNA replication, DNA recombination and DNA repair. During the past five years, the number of DNA polymerases in both eukarya and bacteria has increased to at least 19 and multiple biological roles have been assigned to many DNA polymerases. Archaea, the third domain of life, on the other hand, have only a subset of the eukaryotic-like DNA polymerases. The diversity among the archaeal DNA polymerases poses the intriguing question of their functional tasks. Here, we focus on the two identified DNA polymerases, the family B DNA polymerase B (PabpolB) and the family D DNA polymerase D (PabpolD) from the hyperthermophilic euryarchaeota Pyrococcus abyssi. Our data can be summarized as follows: (i) both Pabpols are DNA polymerizing enzymes exclusively; (ii) their DNA binding properties as tested in gel shift competition assays indicated that PabpolD has a preference for a primed template; (iii) PabPolD is a primer-directed DNA polymerase independently of the primer composition whereas PabpolB behaves as an exclusively DNA primer-directed DNA polymerase; (iv) PabPCNA is required for PabpolD to perform efficient DNA synthesis but not PabpolB; (v) PabpolD, but not PabpolB, contains strand displacement activity; (vii) in the presence of PabPCNA, however, both Pabpols D and B show strand displacement activity; and (viii) we show that the direct interaction between PabpolD and PabPCNA is DNA-dependent. Our data imply that PabPolD might play an important role in DNA replication likely together with PabpolB, suggesting that archaea require two DNA polymerases at the replication fork.     

Profiling the Expression of Genes Controlling Rice Grain Quality

Rice provides a staple source of energy, protein and other nutrients to half of the world population. Over 90 of the rice seeds consists of starch and protein by dry weight. The quantity and property of starch and protein thus play a dominant role in the yield and quality of rice. The amylase content of starch is a determining factor in the eating and cooking quality while the amount and essential amino acids balance of storage proteins affect the nutritional quality of rice. In China, the super-hybrid rice currently under the last phase of development has a 35 yield advantage over the best inbred rice varieties. However, its grain quality needs further improvement. This study reported the expression patterns of 44 genes participating in starch, storage protein, and lysine synthesis in the developing rice grain. Field grown rice cultivar 9311, the paternal line of an elite super-hybrid rice LYP9with its draft genomic sequence released, was used as plant material. Results revealed diverse yet coordinated expression profiles of the genes involved in the three pathways which lead to the final composition and property of starch, protein and lysine that determine the quality of rice, providing useful information for rice quality improvement.     

Suppression of α‐amylase genes improves quality of rice grain ripened under high temperature

High temperature impairs rice (Oryza sativa) grain filling by inhibiting the deposition of storage materials such as starch, resulting in mature grains with a chalky appearance, currently a major problem for rice farming in Asian countries. Such deterioration of grain quality is accompanied by the altered expression of starch metabolism‐related genes. Here we report the involvement of a starch‐hydrolyzing enzyme, α‐amylase, in high temperature‐triggered grain chalkiness. In developing seeds, high temperature induced the expression of α‐amylase genes, namely Amy1A, Amy1C, Amy3A, Amy3D and Amy3E, as well as α‐amylase activity, while it decreased an α‐amylase‐repressing plant hormone, ABA, suggesting starch to be degraded by α‐amylase in developing grains under elevated temperature. Furthermore, RNAi‐mediated suppression of α‐amylase genes in ripening seeds resulted in fewer chalky grains under high‐temperature conditions. As the extent of the decrease in chalky grains was highly correlated to decreases in the expression of Amy1A, Amy1C, Amy3A and Amy3B, these genes would be involved in the chalkiness through degradation of starch accumulating in the developing grains. The results show that activation of α‐amylase by high temperature is a crucial trigger for grain chalkiness and that its suppression is a potential strategy for ameliorating grain damage from global warming.     

开花后水分调控对两个筋型冬小麦品种品质与产量的影响

 通过开花后不同水分处理研究了两个不同筋型冬小麦品种(‘豫麦34’和‘洛阳8716’)(Triticum aestivum cv. `Yumai 34' and `Luoyang 8716')的品质及产量变化。结果表明：随着灌水时间推迟,湿面筋含量、沉降值、面团形成时间、稳定时间、评价值和拉伸面积有提高的趋势,但是千粒重和产量下降;随着开花后灌水量的增加,上述品质数值又有减少,产量及千粒重增加;多次灌水处理与开花后灌1次水处理、开花后不灌水处理之间差异显著,开花后21 d和28 d灌水处理的多项品质指标都大于不灌水处理。两品种面团稳定时间（45%和15%）、沉降值（20%和12%）在不同水分处理下变异系数较大,吸水率、湿面筋、蛋白质含量变异系数（<10%和 <5%）较小。     

Sink development, sucrose metabolising enzymes and carbohydrate status in turnip (Brassica rapa L.)

Accumulation of 60–70 % of biomass in turnip root takes place between 49–56 days after sowing. To understand the phenomenon of rapid sink filling, the activities of sucrose metabolising enzymes and carbohydrate composition in leaf blades, petiole and root of turnip from 42–66 days of growth were determined. An increase (2–3 folds) in glucose and fructose contents of roots accompanied by an increase in activities of acid and alkaline invertases was observed during rapid biomass accumulating phase of roots. The observed decrease in the activities of acid and alkaline invertases along with sucrose synthase (cleavage) in petiole during this period could facilitate unrestricted transport of sucrose from leaves to the roots. During active root filling period, a decrease in sucrose synthase (cleavage) and alkaline invertase activities was also observed in leaf blades. A rapid decline in the starch content of leaf blades was observed during the phase of rapid sink filling. These metabolic changes in the turnip plant led to increase in hexose content (35–37 %) of total dry biomass of roots at maturity. High hexose content of the roots appears to be due to high acid invertase activity of the root.     

重穗型杂交水稻籽粒灌浆过程中强势和强势颖花内源IAA、ABA和GA水平的动态状况

研究了重穗型杂交水稻培矮 6 4s/E3 2的灌浆过程和强、弱势颖花中内源IAA、ABA和GA1 GA3水平的动态状况。籽粒发育过程中不同内源激素水平高低依次为 :IAA >GA1 GA3>ABA。IAA和ABA水平在强势颖花中较高而GA1 GA3水平在弱势颖花中较高。 3种激素水平的变化与谷粒增重速率之间均存在正相关 ,两个最高的相关系数值分别存在于单位鲜重样本的IAA含量(ng/gFW ) 与籽粒鲜重的增重速率之间 (r =0 .82 1 8 )和单个籽粒IAA含量 (ng/grain)与籽粒干重的增重速率之间 (r =0 .8485 )。推测启动和维持籽粒灌浆过程可能需要较高的IAA水平 ;ABA可能具有促进籽粒中同化物的累积和种子成熟的作用 ;GA1 GA3可能具有保持弱势颖花活性的特殊作用     

Relationship between leaf photosynthetic function at grain filling stage and yield in super high-yielding hybrid rice ( Oryza sativa . L)

The characteristics of dry matter production before and after heading and the relationships between photosynthesis of flag leaves and dry matter accumulation in panicles were investigated on super high-yielding rice cv. Xieyou 9308 (the yield of up to 12 t/ha) with rice cv. Xieyou 63 as a control. The results showed that (i) the capacity of dry matter production before and after heading in Xieyou 9308, i.e. biomass and daily dry matter production, was remarkably higher than that in Xieyou 63, especially after heading; (ii) CO₂ assimilation capacity in flag leaves in Xieyou 9308, namely Leaf Source Capacity (LSC), was also significantly higher than that in Xieyou 63, and the supply of photosynthate in leaves and the demand of grain filling were completely synchronous in Xieyou 9308, but photosynthetic function in flag leaves in Xieyou 63 declined sharply 20 days after heading and it was not enough to meet the demand of grain filling. These results confirmed that high efficient photosynthetic function in leaves after heading and its complete synchronization with grain filling are the key approaches to super high yield of rice.     

超大穗小麦籽粒灌浆特性研究

超大穗小麦是小麦超高产育种的宝贵资源,通过去穗处理,对不同类型的超大穗小麦灌浆特性进行了方程拟合及参数分析,结果表明：①百粒重的增重进程,在不同处理间无显著差异,不同品系间差异明显;②单株粒重的增重进程,在不同处理间、不同品系间都表现出显著差异,不同处理间更为突出;③对灌浆参数分析,超大穗小麦的最大灌浆速度与对照基本一致,但灌浆期显著的长,８６（３０６）达５０d,90(151)43d,而对照小偃６号、咸农１５１分别为４０d,35d。依次配合相应的栽培技术,可有效的发挥超大穗小麦产量潜力。     

安徽繁昌晚新生代裂隙堆积中的松鼠类化石（英文）

描述了安徽繁昌癞痢山塘口晚新生代裂隙堆积物中发现的松鼠类材料。化石代表松鼠亚科的4个族,共有5属6种,其中包括一个新属和两个新种,即树松鼠族的Sciurus sp.,花鼠族的Tamias sp.和Plesiosciurus zhengi sp.nov.,旱獭族的Sciurotamias wangi Qiu,2002和S.teilhardi Zheng,1993,以及巨松鼠族的Pseudoratufa wanensis gen.et sp.nov.。所研究的材料系混合地采自同一裂隙堆积的4个不同层位,化石的组分可能代表从早中新世至更新世的不同时段。繁昌的这一松鼠组合具有中国中南部晚新生代松鼠动物群的特色,并含有稀奇的Pseudoratufa属。该新属的牙齿形态显示了其树栖松鼠的特征,而且可以归入甚为稀有的巨松鼠族。其遗骸具有与该地点发现的古猿、硅藻鼠和河狸类化石相似的石化和堆积过程,似乎表明这些动物属于时代相同或较接近的群体,它们的共存也说明了繁昌地区在中新世时有过相对湿润的森林生境。     

控灌对小麦植株体内激素含量与籽粒灌浆速率的影响

利用防雨棚研究了控灌对小麦植株体内激素含量与籽粒不乐速率的影响。结果表明：随控水加重,小麦旗叶、根系和籽粒中ＡＢＡ含量迅速达到高峰,然后快速降低;控水愈重,ｉ－ＰＡｓ峰值和籽粒灌浆速率峰值出现愈早,尔后下降,从而加速了植株衰老进程,导致产量降低。籽粒灌浆速率变化与旗叶,根主籽粒中激素含量变化呈极显著相关,且上述性状在相对含水量６０％处理下与８０％（对照）相比无显著差异,从而为小麦节水栽培提供了依据