Gene expression of the biosynthetic enzymes and biosynthesis of starch during Rice Grain development

Amylose and amylopectin are determinants of the physicochemical properties for starch and grain quality in rice. Their biosynthesis is catalyzed by the interplay of ADP-glucose pyrophosphorylase (AGPase), granule-bound starch synthase (GBSS), soluble starch synthase (SSS), a starch branching enzyme (SBE), and a starch debranching enzyme (SDE). In this study, the genes for these enzymes were highly expressed 7 to 28 days after flowering during grain development, and their expression closely matched increases in both starch content and grain weight Among all the tested cultivars, amylose contents in the rice grains remained essentially constant throughout their development The AGPase gene was highly expressed in the high-yield cultivars of both glutinous and non-glutinous rice. The SSS gene was actively expressed when mature GBSS mRNA decreased. Genes responsible for amylopectin biosynthesis were simultaneously expressed in the late stage of grain development. We have now demonstrated that the expression patterns of starch biosynthetic genes differ between glutinous and non-glutinous rice, and between Tongil (a Japonica/ Indica hybrid) and Japonica types.     

Differential modulation of murine host immune response by salivary gland extracts from the mosquitoes Aedes aegypti and Culex quinquefasciatus

Mosquitoes (Diptera: Culicidae) are major vectors of numerous infectious agents. Compounds in mosquito saliva not only facilitate blood-feeding, but may also have an impact upon the immune system of vertebrate hosts. Consequently, the exposure to mosquito saliva may influence pathogen transmission, establishment and disease development. Using two medically important vector mosquitoes, Aedes aegypti (L.) and Culex quinquefasciatus Say, we examined the effects of mosquito saliva on immune cells of host mice. After antigen-specific or non-specific stimulation, murine splenocyte proliferation and production of both Th1 and Th2 cytokines were significantly reduced in the presence of salivary gland extract (SGE) from Ae. aegypti, but not SGE from Cx. quinquefasciatus. T cell populations were highly susceptible to this suppression, showing increased mortality and reduced division rates - judged by flow cytometric analyses. Evidently these two culicine mosquitoes differ in their host immunomodulatory activities.     

Adding a selective enrichment step to the iQ-Check real-time PCR improves the detection of Salmonella in naturally contaminated retail turkey meat products

AIMS: The aim of this study was to compare the real-time iQ-Check Salmonella kit (Bio-Rad) with the immunocapture assay RapidCheck Salmonella method, and a conventional culture method (FSIS, USDA) in detecting Salmonella in naturally contaminated turkey meat products. This study was also designed to determine if a selective enrichment step might improve the real-time detection of Salmonella. METHODS AND RESULTS: Using the culture method, Salmonella was recovered from 49 out of 99 retail turkey meat samples collected. RapidCheck failed to detect 11 Salmonella samples that were positive by the culture method. The iQ-Check real-time PCR also failed to detect three samples that were positive by the culture method. However, when carried out after a selective enrichment step, the iQ-Check real-time PCR detected all 49 Salmonella samples recovered by the culture method. The iQ-Check real-time PCR detected the presence of Salmonella in some samples that were not recovered by the culture method. CONCLUSIONS: Adding a selective enrichment step to the iQ-Check real-time PCR improves the detection of Salmonella in naturally contaminated turkey meat samples. SIGNIFICANCE AND IMPACT OF THE STUDY: The iQ-Check Salmonella real-time PCR can be used as a rapid method to monitor Salmonella in turkey meat, together with conventional culture methodology.     

Brassinosteroid-induced rice lamina joint inclination and its relation to indole-3-acetic acid and ethylene

Brassinosteroid (BR)-induced rice (Oriza sativa L.) lamina joint (RLJ) inclination and its relationship to indole-3-acetic acid (IAA) and ethylene were investigated using BR isolated from beeswax. The effect of BR on RLJ inclination was time- and concentration-dependent. Etiolated lamina were more sensitive to BR than green lamina. The BR-induced inclination was accompanied by increased lamina fresh weight, total water content, free-water content, proton extrusion and ethylene production, and decreased bound-water content. Lamina dry weight was not changed. The inclination was due to greater expansion of the adaxial cells relative to the dorsal cells in the lamina joint. This response was caused by BR and/or BR-induced signal(s) that were transported from the leaf sheath to the leaf blade. Both BR-induced RLJ inclination and ethylene production were inhibited by cobalt chloride (CoCl₂), an inhibitor of ACC oxidase. BR-induced inclination was much higher than that of IAA, and was inhibited by high concentration of 2,3,5-triiodobenzoic acid (TIBA), an inhibitor of IAA transport. A synergistic effect was observed between BR and IAA. These results suggest that the effects of BR on RLJ inclination and pulvinus cell expansion may be resulted from BR-increased water potential and proton extrusion in the lamina. The BR-induced RLJ inclination may involve the action of ethylene but may be independent of IAA.Abbreviations BR brassinolide or brassinosteroid(s) - IAA indole-3-acetic acid - TIBA 2,3,5-triiodobenzoic acid - RLJ rice lamina joint     

Construction of a Microsatellite Linkage Map with Two Sequenced Rice Varieties

Based on the successful development of new microsatellite markers from the data of two whole-sequenced rice varieties, japonica variety Nipponbare and indica variety 9311, an F₂ population of 90 lines, which was derived from a single cross between Nipponbare and 9311, was applied to construct a genetic linkage framework map. The map covered 2 455.7 cM of total genomic length, and consisted of 152 simple sequence repeats (SSRs) loci including 46 pairs of new SSR primers developed by our research institute. The average genetic distance between two markers was 16.16 cM. In addition, markers RM345 and RM494, which have not been mapped on the Temnykh's map et al. (2001) were anchored on the sixth chromosome of this map. We compared this research with maps of Temnykh et al.(2001) and LAN et al. (2003) regarding the aspects of type and size of population, type and quantity of markers, and the marker arrangement order on chromosome, etc. Results indicated that the similarity of marker linear alignment was 93.81% between this map and T-map, Finally, the important significance of using sequenced rice varieties to construct linkage map was also discussed.     

生长素调控植物重力反应的分子机理研究

重力反应是植物对环境的一种适应现象。生长素参与植物环境适应与发育调控的过程,重力反应过程的核心之一是在重力反应器官形成生长素的浓度梯度,诱导下游基因的差异表达。生长素的合成、代谢、极性运输及信号转导在此过程中发挥了关键作用。该文以拟南芥和水稻的研究为基础,综述了近几年对生长素调控植株重力反应的分子机理的研究进展,并对该领域未来的研究进行展望。     

水稻抗逆相关基因的分子进化分析

植物在进化过程中为了适应外界环境,已经具有一套完整的抵抗外界特殊环境的调控系统。但是,关于水稻抗逆相关基因的分子进化方面的研究还未见报道。文章通过Plant Tolerance Gene Database数据库,获得22个水稻抗逆相关基因。利用比较基因组学和生物信息学方法对水稻抗逆相关基因的进化动态进行研究,结果表明水稻抗逆相关基因在低等植物中比较保守;随着植物的不断进化和生存环境的改变,其基因数量也随之增加。具有相似抗性功能的基因往往具有相似的基因结构和基序(motif)结构。文章还发现4个保守motif 的存在：HRDXK、DXXSXG、LLPR和GXGXXG(X代表任意氨基酸)。在GSK1、RAN2抗逆基因中发现了3个特有的motif结构：GSK1特有的P-rich motif,RAN2特有的G-rich motif和E-rich motif。推测这些保守的motif结构与基因的抗逆功能密切相关。进化速率分析结果表明,尽管植物抗逆性相关基因在进化过程中受到较强的纯化选择作用,但是仍然有50%的抗逆性相关基因存在正选择位点。这些正选择位点的存在有可能为基因适应外界环境变化提供了重要的物质基础。     

Enhanced fungal resistance in Arabidopsis expressing wild rice PR-3 (OgChitIVa) encoding chitinase class IV

Oryza grandiglumis Chitinase IVa (OgChitIVa) cDNA encoding a class IV chitinase was cloned from wild rice (Oryza grandiglumis). OgChitIVa cDNA contains an open reading frame of 867 nucleotides encoding 288 amino acid residues with a predicted molecular weight of 30.4 kDa and isoelectric point of 8.48. Deduced amino acid sequences of OgChitIVa include the signal peptide and chitin-binding domain in the N-terminal domain and conserved catalytic domain. OgChitIVa showed significant similarity at the amino acid level with related monocotyledonous rice and maize chitinase, but low similarity with dicotyledoneous chitinase. Southern blot analysis showed that OgChitIVa genes are present as two copies in the wild rice genome. It was shown that RNA expression of OgChitIVa was induced by defense/stress signaling chemicals, such as jasmonic acid, salicylic acid, and ethephon or cantharidin and endothall or wounding, and yeast extract. It was demonstrated that overexpression of OgChitIVa in Arabidopsis resulted in mild resistance against the fungal pathogen, Botrytis cinerea, by lowering disease rate and necrosis size. RT-PCR analysis showed that PR-1 and PR-2 RNA expression was induced in the transgenic lines. Here, we suggest that a novel OgChitIVa gene may play a role in signal transduction process in defense response against B. cinerea in plants. J.-H. Pak and E.-S. Chung contributed equally to this work.