Rice sulfoquinovosyltransferase SQD2.1 mediates flavonoid glycosylation and enhances tolerance to osmotic stress

Sulfoquinovosyltransferase 2 (SQD2) catalyses the final step in the sulfoquinovosyldiacylglycerol (SQDG) biosynthetic pathway. It is involved in the phosphate starvation response. Here, we show that rice SQD2.1 has dual activities catalysing SQDG synthesis and flavonoid glycosylation. SQD2.1 null mutants (sqd2.1) in rice had decreased levels of glycosidic flavonoids, particularly apigenin 7‐O‐glucoside (A7G), whereas these metabolites were increased in rice plants overexpressing SQD2.1. The sqd2.1 mutants and SQD2.1 overexpressing lines showed reduced and enhanced, respectively, tolerance to salinity and drought. Treating the sqd2.1 mutants with A7G decreased oxidative damage and restored stress tolerance to the wild‐type levels. These findings demonstrate that SQD2.1 has a novel function in the glycosylation of flavonoids that is required for osmotic stress tolerance in rice. The novel activity of SQD2.1 in the production of glycosidic flavonoids improves scavenging of reactive oxygen species and protects against excessive oxidation.     

The nuclear localization signal and the C-terminal region of FHY1 are required for transmission of phytochrome A signals

Plants use the family of phytochrome photoreceptors to sense their light environment in the red/far-red region of the spectrum. Phytochrome A (phyA) is the primary photoreceptor that regulates germination and early seedling development. This phytochrome mediates seedling de-etiolation for the developmental transition from heterotrophic to photoauxotrophic growth. High intensity far-red light provides a way to specifically assess the role of phyA in this process and was used to isolate phyA-signaling intermediates. fhy1 and pat3 (renamed fhy1-3) are independently isolated alleles of a gene encoding a phyA signal transduction component. FHY1 is a small 24 kDa protein that shows no homology to known functional motifs, besides a small conserved septin-related domain at the C-terminus, a putative nuclear localization signal (NLS) and a putative nuclear exclusion signal (NES). Here we demonstrate that the septin-related domain is important for FHY1 to transmit phyA signals. Moreover, the putative NLS and NES of FHY1 are indeed involved in its nuclear localization and exclusion. Nuclear localization of FHY1 is needed for it to execute responses downstream of phyA. Together with the results from global expression analysis, our findings point to an important role of FHY1 in phyA signaling through its nuclear translocation and induction of gene expression.     

<Emphasis Type="Italic">ASYMMETRIC LEAVES1</Emphasis>, an <Emphasis Type="Italic">Arabidopsis</Emphasis> gene that is involved in the control of cell differentiation in leaves

During leaf development, the formation of dorsal-ventral and proximal-distal axes is central to leaf morphogenesis. To investigate the genetic basis of dorsoventrality and proximodistality in the leaf, we screened for mutants of Arabidopsis thaliana (L.) Heynh. with defects in leaf morphogenesis. We describe here the phenotypic analysis of three mutant alleles that we have isolated. These mutants show varying degrees of abnormality including dwarfism, broad leaf lamina, and aberrant floral organs and fruits. Genetic analysis revealed that these mutations are alleles of the previously isolated mutant asymmetric leaves1 ( as1). In addition to the leaf phenotypes described previously, these alleles display other phenotypes that were not observed. These include: (i) some rosette leaves with petiole growth underneath the leaf lamina; (ii) leaf vein branching in the petiole; and (iii) a leaf lamina with an epidermis similar to that on the petiole. The mutant phenotypes suggest that the ASYMMETRIC LEAVES1 ( AS1) gene is involved in the control of cell differentiation in leaves. As the first step in determining a molecular function for AS1, we have identified the AS1 gene using map-based cloning. The AS1 gene encodes a MYB-domain protein that is homologous to the Antirrhinum PHANTASTICA ( PHAN) and maize ROUGH SHEATH2 ( RS2) genes. AS1 is expressed nearly ubiquitously, consistent with the pleiotropic mutant phenotypes. High levels of AS1 expression were found in tissues with highly proliferative cells, which further suggests a role in cell division and early cell differentiation.     

Isolation and functional analysis of a Brassica juncea gene encoding a com-ponent of auxin efflux carrier

Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsis pin gene family was believed to encode a component of auxin efflux carrier (G(?)lweiler et al, 1998). Based on the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpin1), which encoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level with AtPINl and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homology to AtPIN3). Hydrophobic analysis showed similar structures between BjPINl and AtPIN proteins. Presence of 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp) in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blot analysis indicated that Bjpin1 was expressed in most of the tissues tested, with a relatively h     

Environmental controls over carbon exchange of three forest ecosystems in eastern China

Net ecosystem productivity (NEP) was continuously measured using the eddy covariance (EC) technique from 2003 to 2005 at three forest sites of ChinaFLUX. The forests include Changbaishan temperate mixed forest (CBS), Qianyanzhou subtropical coniferous plantation (QYZ), and Dinghushan subtropical evergreen broad‐leaved forest (DHS). They span wide ranges of temperature and precipitation and are influenced by the eastern Asian monsoon climate to varying extent. In this study, we estimated ecosystem respiration (RE) and gross ecosystem productivity (GEP). Comparison of ecosystem carbon exchange among the three forests shows that RE was mainly determined by temperature, with the forest at CBS exhibiting the highest temperature sensitivity among the three ecosystems. The RE was highly dependent on GEP across the three forests, and the ratio of RE to GEP decreased along the North–South Transect of Eastern China (NSTEC) (i.e. from the CBS to the DHS), with an average of 0.77 ± 0.06. Daily GEP was mainly influenced by temperature at CBS, whereas photosynthetic photon flux density was the dominant factor affecting the daily GEP at both QYZ and DHS. Temperature mainly determined the pattern of the interannual variations of ecosystem carbon exchange at CBS. However, water availability primarily controlled the interannual variations of ecosystem carbon exchange at QYZ. At DHS, NEP attained the highest values at the beginning of the dry seasons (autumn) rather than the rainy seasons (summer), probably because insufficient radiation and frequent fog during the rainy seasons hindered canopy photosynthesis. All the three forest ecosystems acted as a carbon sink from 2003 to 2005. The annual average values of NEP at CBS, QYZ, and DHS were 259 ± 19, 354 ± 34, and 434 ± 66 g C m⁻² yr⁻¹, respectively. The slope of NEP that decreased with increasing latitude along the NSTEC was markedly different from that observed on the forest transect in the European continent. Long‐term flux measurements over more forest ecosystems along the NSTEC will further help verify such a difference between the European forest transect and the NSTEC and provide insights into the responses of ecosystem carbon exchange to climate change in China.     

肺炎链球菌SP0306蛋白的表达纯化及结晶研究

SP0306蛋白是肺炎链球菌TIGR4菌株中的一种假想的转录因子,但其蛋白三维结构及生物学功能尚未明了,生物信息学分析提示其可能调控碳水化合物代谢相关基因的表达。成功构建了SP0306蛋白的全长表达载体PET28a-sp0306,利用大肠杆菌BL21(DE3)菌株进行原核表达,获得了以可溶形式表达的目的蛋白。经Ni-NTA柱亲和层析及DEAE阴性离子交换层析纯化后,获得了高纯度的目的蛋白。采用悬滴气相扩散法获得了质量较好的SP0306蛋白晶体,并初步进行了晶体X射线衍射,为其最终的三维结构解析及生物学功能研究奠定了基础。     

酿酒酵母乙醇脱氢酶2(ADH2)基因的克隆表达及活性验证

为了从酿酒酵母Saccharomyces cerevisiae中克隆出乙醇脱氢酶2(Alcoholdehy drogenase2,ADH2)基因并使之在大肠杆菌中高效表达。以酿酒酵母细胞中提取的总RNA为模板,通过反转录获得酿酒酵母乙醇脱氢酶2基因,连接到表达载体pTAT上,得到重组表达质粒pTAT-ADH2,将此重组质粒转化到大肠杆菌BL21中,重组工程菌株经IPTG诱导表达得到ADH2蛋白。将该蛋白纯化后,在体外进行活性检测和小鼠体内进行毒理试验,检测ADH2的酶活性。测序结果表明克隆的基因与GenBank中所报道的adh2基因序列有90%的同源性,经SDS-PAGE电泳分析,目的蛋白得到了有效表达,蛋白条带扫描分析表明,表达量占总蛋白的50%左右,纯化得到的蛋白在小鼠体内进行毒理试验,显示出一定的活性。酿酒酵母adh2基因的克隆正确,不仅在大肠杆菌中进行了高效表达而且表现出了较好的酶活性。     

Long Non-coding RNA ANRIL Downregulation Alleviates Neuroinflammation in an Ischemia Stroke Model via Modulation of the miR-671-5p/NF-κB Pathway

Neurochemical Research - The aim of this study was to investigate the role and underlying mechanism of the long non-coding RNA ANRIL (antisense noncoding RNA in the INK4 locus, ANRIL) in ischemia...