死亡信号传递: 叶绿体与线粒体间信号交流调控植物程序性细胞死亡

程序性细胞死亡(PCD)是生物体受遗传调控的自主细胞死亡现象, 在植物生长发育和抵抗环境胁迫中起重要作用。PCD的发生可受线粒体中活性氧(ROS)诱导。中国科学院遗传与发育生物学研究所李家洋研究组早期的研究发现了1个拟南芥(Arabidopsis thaliana)细胞死亡突变体mod1, 并暗示植物细胞中存在叶绿体与线粒体之间的信号交流调控PCD, 但其中的具体作用机制尚不清楚。最近, 他们通过大规模筛选mod1突变体的抑制突变体, 克隆了3个新的抑制基因plNAD- MDH、DiT1和mMDH1。此3个基因分别编码质体定位的NAD依赖的苹果酸脱氢酶、叶绿体被膜定位的二羧酸转运蛋白1和线粒体定位的苹果酸脱氢酶1, 突变后都可抑制mod1中ROS的积累及PCD的发生。通过对这些基因进行深入的功能分析, 他们论证了苹果酸从叶绿体到线粒体的转运对线粒体中ROS的产生及随后PCD的诱导起重要作用。该研究拓展了我们对植物细胞中细胞器间交流的认识, 为我们深入理解植物PCD发生机制提供了新线索, 是该领域的一项突破性进展。     

Reverse Genetic Identification of CRN1 and its Distinctive Role in Chlorophyll Degradation in Arabidopsis

Recent identification of NYE1/SGR1 brought up a new era for the exploration of the regulatory mechanism of Chlorophyll (Chl) degradation.Cluster analysis of senescence associated genes with putative chloroplast targeting sequences revealed several genes sharing a similar expression pattern with NYE1.Further characterization of available T-DNA insertion lines led to the discovery of a novel stay-green gene CRN1 ((C)o-(r)egulated with (N)YE1).Chl breakdown was significantly restrained in crn1-1 under diversified senescence scenarios,which is comparable with that in acd1-20,but much more severe than that in nye1-1.Notably,various Chl binding proteins,especially trimeric LHCP Ⅱ,were markedly retained in crn1-1 four days after dark-treatment,possibly due to a lesion in disassociation of protein-pigment complex.Nevertheless,the photochemical efficiency of PSII in crn1-1 declined,even more rapidly,two days after dark-treatment,compared to those in Col-0 and nye1-1.Our results suggest that CRN1 plays a crucial role in Chl degradation,and that loss of its function produces various side-effects,including those on the breakdown of Ch-protein complex and the maintenance of the residual photosynthetic capability during leaf senescence.     

植物NAC转录因子家族研究概况

植物特有的NAC家族转录因子数量众多, 广泛分布于陆生植物中。NAC转录因子涉及多个生长发育和胁迫应答过程,功能多样而重要, 从发现至今一直是研究的热点。ANAC019蛋白三维结构的解析和一系列NAC基因功能的揭示可以帮助我们更全面地了解NAC家族, 包括它们的起源与分类、生物学功能、表达调控规律以及结构与功能的关系。该文较为详尽地阐述了NAC家族转录因子的研究现状, 并展望其未来的研究方向。     

Rapid and Simple Method for the Most-Probable-Number Estimation of Arsenic-Reducing Bacteria

A rapid and simple most-probable-number (MPN) procedure for the enumeration of dissimilatory arsenic-reducing bacteria (DARB) is presented. The method is based on the specific detection of arsenite, the end product of anaerobic arsenate respiration, by a precipitation reaction with sulfide. After 4 weeks of incubation, the medium for the MPN method is acidified to pH 6 and sulfide is added to a final concentration of about 1 mM. The brightly yellow arsenic trisulfide precipitates immediately and can easily be scored at arsenite concentrations as low as 0.05 mM. Abiotic reduction of arsenate upon sulfide addition, which could yield false positives, apparently produces a soluble As-S intermediate, which does not precipitate until about 1 h after sulfide addition. Using the new MPN method, population estimates of pure cultures of DARB were similar to direct cell counts. MPNs of environmental water and sediment samples yielded DARB numbers between 10¹ and 10⁵ cells per ml or gram (dry weight), respectively. Poisoned and sterilized controls showed that potential abiotic reductants in environmental samples did not interfere with the MPN estimates. A major advantage is that the assay can be easily scaled to a microtiter plate format, enabling analysis of large numbers of samples by use of multichannel pipettors. Overall, the MPN method provides a rapid and simple means for estimating population sizes of DARB, a diverse group of organisms for which no comprehensive molecular markers have been developed yet.     

同域分布垂穗披碱草和达乌力披碱草遗传多样性和遗传结构分析

披碱草属(Elymus L.)是禾本科(Poaceae)小麦族(Triticeae)中的一个多年生属,该属在青藏高原地区有广泛分布,多数物种是草原和草甸的组成成分,许多种类为品质优良的牧草.垂穗披碱草(E.nutans)和达乌力披碱草(E.dahuricus)同为禾本科小麦族披碱草属异源六倍体物种,染色体组组成皆为St...     

Risk assessment of land ecology on a regional scale: Application of the relative risk model to the mining city of Daye,China

The ecological risk assessment of land ecosystems plays a vital role in land environment protection and management in China. To identify the ecological impairment in land ecosystems, risk assessment of regional land ecology was conducted in Daye, a traditional mining city in Central China, using the relative risk model (RRM). The study area was divided into six sub-regions; and the sources, stressors, habitats, and end points of the impairment were identified. A conceptual model was built to represent the ecological interactions among risk components. Results showed the following: (1) The traditional iron–coal mining sub-region and the mineral processing sub-region exhibited high risk. (2) Mining was the largest risk source, followed by solid waste piling and urbanization. (3) Disappearance of habitats was the greatest risk stressor, followed by the accumulation of pollutants and heavy metals. (4) Among the eight identified habitats, the lake habitat was the most likely to be affected. (5) Health threats, soil contamination, and landscape aesthetic dysfunctions appeared to be the end points under the largest risk pressure. Finally, Monte Carlo analysis was used to evaluate the effects of uncertainty on risk model predictions. Our assessment model was proven to be generally valid for regional land ecology risk assessment.     

Site-specific N-glycosylation identification of recombinant human lectin-like oxidized low density lipoprotein receptor-1 (LOX-1)

Human LOX-1/OLR 1 plays a key role in atherogenesis and endothelial dysfunction. The N-glycosylation of LOX-1 has been shown to affect its biological functions in vivo and modulate the pathogenesis of atherosclerosis. However, the N-glycosylation pattern of LOX-1 has not been described yet. The present study was aimed at elucidating the N-glycosylation of recombinant human LOX-1 with regard to N-glycan profile and N-glycosylation sites. Here, an approach using nonspecific protease (Pronase E) digestion followed by MALDI-QIT-TOF MS and multistage MS (MS(3)) analysis is explored to obtain site-specific N-glycosylation information of recombinant human LOX-1, in combination with glycan structure confirmation through characterizing released glycans using tandem MS. The results reveal that N-glycans structures as well as their corresponding attached site of LOX-1 can be identified simultaneously by direct MS analysis of glycopeptides from non-specific protease digestion. With this approach, one potential glycosylation site of recombinant human LOX-1 on Asn(139) is readily identified and found to carry heterogeneous complex type N-glycans. In addition, manual annotation of multistage MS data utilizing diagnostic ions, which were found to be particularly useful in defining the structure of glycopeptides and glycans was addressed for proper spectra interpretation. The findings described herein will shed new light on further research of the structure-function relationships of LOX-1?N-glycan.     

Extensive sharing of chloroplast haplotypes among East Asian Cerris oaks: The imprints of shared ancestral polymorphism and introgression

Shared ancestral polymorphism and introgression are two main causes of chloroplast DNA (cpDNA) haplotype sharing among closely related angiosperms. In this study, we explored the roles of these two processes in shaping the phylogeographic patterns of East Asian Cerris oaks by examining the geographic distributions of randomly and locally distributed shared haplotypes, which coincide with the expectations of shared ancestry and introgression, respectively. We sequenced 1340 bp of non‐coding cpDNA from Quercus acutissima (n = 418) and Q. chenii (n = 183) and compiled previously published sequence data of Q. variabilis (n = 439). The phylogenetic relationships among haplotypes were examined using a median‐joining network. The geographic patterns of interspecifically shared haplotypes were assessed to test whether nearby populations have a higher degree of interspecific cpDNA sharing than distant ones. We identified a total of 27 haplotypes that were grouped into three non‐species‐specific lineages with overlapping distributions. Ancestral haplotypes were extensively shared and randomly distributed across populations of the three species. Some young haplotypes were locally shared in mountainous areas that may have been shared refugia. The local exchange of cpDNA resulted in an excess of similar haplotypes between nearby populations. Our study demonstrated that the haplotype sharing pattern among East Asian Cerris oaks reflected the imprints of both shared ancestral polymorphism and introgression. This pattern was also associated with the relatively stable climates and complex landscapes in East Asia, which not only allowed the long‐term persistence of ancestral lineages but also connected the survived populations across refugia.     

邻单胞菌邻苯二酚1,2-双加氧酶基因(tfd C)的克隆及其在大肠杆菌中表达

根据已报道的邻苯二酚１,２－双加氧酶基因（ｔｆｄ Ｃ）序列,设计ＰＣＲ引物,从一株邻单胞菌（Ｐｌｅｓｉｏｍｉｎａｓ）的ｐＬ１质粒上扩增到ｔｆｄ Ｃ基因片段,连接到ｐＧＥＭ－Ｔ载体上,并转化大肠杆菌ｌＭ１０９菌株,筛选到阳性克隆。序列分析结果表明,ＰＣＲ产物全长８０１ｂｐ,有一阅读框,编码２５５个氨基酸,与增氧产碱菌（Ａｌｃａｌｉｇｅｎｅｓ ｅｕｔｒｏｐｌｕｓ）的ｔｆｄ Ｃ基因相比,在６９３位相差一