The rna2 mutation of yeast affects the processing of actin mRNA as well as ribosomal protein mRNAs

The temperature sensitive rna2 mutation of Saccharomyces cerevisiae causes a rapid and dramatic decrease in the abundance of most ribosomal protein mRNAs We and others have recently shown that the processing of ribosomal protein mRNAs is defective at the nonpermissive temperature, suggesting that inefficient mRNA processing might be responsible for the decline in ribosomal protein mRNA levels. Actin is the only known intron-containing non-ribosomal protein yeast nuclear gene We show here that the processing of actin mRNA is also defective at the nonpermissive temperature in rna2-containing strains. The observation supports the notion that all intron-containing genes are affected in a similar fashion by the rna2 mutation.     

水稻OsRPL36A基因的表达特性研究

【目的】核糖体蛋白（ribosomal protein,RP）是参与蛋白质合成及基因表达调控的一种重要因子,在植物生长发育和胁迫响应过程中具有重要的作用。研究在水稻中克隆了1个核糖体蛋白家族基因OsRPL36A,并对其生物学功能进行初步研究,为后续OsRPL36A基因功能研究提供理论依据和研究方向。【方法】利用生物信息学技术分析OsRPL36A基因结构、顺式作用元件和演化过程;同时利用实时荧光定量PCR（quantitative real-time PCR,qRT-PCR）技术分析OsRPL36A的组织表达特异性、节律表达模式、及其对不同激素和非生物胁迫的响应情况。【结果】（1）OsRPL36A的编码区全长为297 bp,共编码98个氨基酸,属于核糖体蛋白L36超基因家族。（2）OsRPL36A的启动子区包含3个节律表达相关元件、10个光响应元件、14个激素响应元件和27个环境胁迫响应元件。（3）OsRPL36A在叶片中的表达量相对高于其他组织;具有典型的节律表达模式;且受IAA、高温、低温和渗透胁迫等诱导表达。【结论】OsRPL36A在叶中高表达,具有典型节律表达模式,对IAA显著响应,可能参与热激、低温、盐害和渗透胁迫响应。     

The ancient subclasses of Arabidopsis Actin Depolymerizing Factor genes exhibit novel and differential expression

The Actin Depolymerizing Factor (ADF) gene family of Arabidopsis thaliana encodes 11 functional protein isovariants in four ancient subclasses. We report the characterization of the tissue-specific and developmental expression of all Arabidopsis ADF genes and the subcellular localization of several protein isovariants. The four subclasses exhibited distinct expression patterns as examined by qRT-PCR and histochemical assays of a GUS reporter gene under the control of individual ADF regulatory sequences. Subclass I ADFs were expressed strongly and constitutively in all vegetative and reproductive tissues except pollen. Subclass II ADFs were expressed specifically in mature pollen and pollen tubes or root epidermal trichoblast cells and root hairs, and these patterns evolved from an ancient dual expression pattern comprised of both polar tip growth cell types, still observed in the monocot Oryza sativa. Subclass III ADFs were expressed weakly in vegetative tissues, but were strongest in fast growing and/or differentiating cells including callus, emerging leaves, and meristem regions. The single subclass IV ADF was constitutively expressed at moderate levels in all tissues, including pollen. Immunocytochemical analysis with subclass-specific monoclonal antibodies demonstrated that subclass I isovariants localize to both the cytoplasm and the nucleus of leaf cells, while subclass II isovariants predominantly localize to the cytoplasm at the tip region of elongating root hairs and pollen tubes. The distinct expression patterns of the ADF subclasses support a model of ADF s co-evolving with the ancient and divergent actin isovariants.     

Non-redundant functions of sHSP-CIs in acquired thermotolerance and their role in early seed development in Arabidopsis

Heat-shock proteins (HSPs) are a group of evolutionarily conserved polypeptides whose expression is induced in all organisms in response to environmental stresses and during various developmental processes. In this work, we show that the rose (Rosa hybrida) cytoplasmic 17.5-kDa Class I small HSP (sHSP17.5-CI, accession number: BQ103946) increases dramatically during flower development, and accumulates in closed bud petals and leaves only in response to heat stress. mRNA for a putative ortholog of this protein is also found in petals, but not leaves, of Arabidopsis (Arabidopsis thaliana) plants grown under optimal conditions, and it accumulates in leaves in response to heat stress. Analysis of Arabidopsis T-DNA insertion lines affected at three homologous genes revealed that their acquired thermotolerance, as measured by hypocotyl-elongation assay, is impaired. The correlation between sHSP-CI accumulation and expansion of rose petal cells, impairment of acquired thermotolerance, and defects in early embryogenesis of the double mutants (hsp17.4/hsp17.6A), all suggest that sHSP-CI proteins play a role in protecting cell proteins at various developmental stages, whereas in hypocotyl elongation they have a non-redundant function in acquired thermotolerance but have a redundant function in early embryogenesis.     

Gene-specific expression of the actin multigene family of Dictyostelium discoideum

We have investigated the expression of 14 cloned genes of the 20-member actin multigene family of Dictyostelium discoideum using gene-specific mRNA complementary probes and an RNase protection assay. Actin gene expression was studied in vegetative cells and in cells at a number of developmental stages chosen to represent the known major shifts in actin mRNA and protein synthesis. At least 13 of these genes are expressed. A few genes are expressed very abundantly at 10% or more of total actin mRNA; however, the majority are maximally expressed at 1 to 5% of actin message. Although all of the genes are transcribed in vegetative cells, most genes appear to be independently regulated. Actin 8 appears to be transcribed at constant, high levels throughout growth and development. Actin 12 mRNA is maximally expressed in vegetative cells but the level is reduced appreciably by the earliest stage of development examined, while Actin 7 mRNA is specifically induced approximately sevenfold at this time. The rest of the genes appear to be induced 1.5 to 2-fold early in development, coincident with the increase in total actin mRNA. Since 12 of the genes code for extremely homologous proteins, it is possible that the large number of actin genes in Dictyostelium is utilized for precise regulation of the amount of actin produced at any stage of development, even though individual gene expression appears in some cases to be very stage-specific. In addition to these 13 actin genes, at least two and possibly four more genes are known to be expressed, because they are represented by complementary DNA clones, and an additional one or two expressed genes are indicated by primer extension experiments. Only one known gene, Actin 2-sub 2, is almost certainly a pseudogene. Thus the vast majority of Dictyostelium actin genes are expressed.     

Heat stress-induced H2O2 is required for effective expression of heat shock genes in Arabidopsis

The mechanisms of sensing and signalling of heat and oxidative stresses are not well understood. The central question of this paper is whether in plant cells oxidative stress, in particular H₂O₂, is required for heat stress- and heat shock factor (HSF)-dependent expression of genes. Heat stress increases intracellular accumulation of H₂O₂ in Arabidopsis cell culture. The accumulation was greatly diminished using ascorbate as a scavenger or respectively diphenyleneiodonium chloride (DPI) as an inhibitor of reactive oxygen species production. The mRNA of heat shock protein (HSP) genes, exemplified by Hsp17.6, Hsp18.2, and the two cytosolic ascorbate peroxidase genes Apx1, Apx2, reached similar levels by moderate heat stress (37°C) or by treatment with H₂O₂, butylperoxide and diamide at room temperature. The heat-induced expression levels were significantly reduced in the presence of ascorbate or DPI indicating that H₂O₂ is an essential component in the heat stress signalling pathway. Rapid (15 min) formation of heat shock promoter element (HSE) protein-binding complex of high molecular weight in extracts of heat-stressed or H₂O₂-treated cells and the inability to form this complex after ascorbate treatment suggests that oxidative stress affects gene expression via HSF activation and conversely, that H₂O₂ is involved in HSF activation during the early phase of heat stress. The heat stress induction of a high mobility HSE-binding complex, characteristic for later phase of heat shock response, was blocked by ascorbate and DPI. H₂O₂ was unable to induce this complex suggesting that H₂O₂ is involved only in the early stages of HSF activation. Significant induction of the genes tested after diamid treatment and moderate expression of the sHSP genes in the presence of 50 mM ascorbate at 37°C occurred without activation of HSF, indicating that other mechanisms may be involved in stress signalling. Electronic Supplementary Material Supplementary material is available for this article at http//dx.doi.org/10.1007/s11103-006-0045-4 Roman A. Volkov and Irina I. Panchuk contributed equally     

Local and differential control of vegetative storage protein expression in response to herbivore damage in Arabidopsis thaliana

Vegetative storage proteins (VSPs) are thought to fulfil important nutritional roles during plant development and stress adaptation. Plant responses to mechanical wounding and herbivore damage include an activation of VSP expression. It was recently suggested that vsp is part of the systemic response of Arabidopsis to wounding. To test this proposal, we monitored the spatial regulation of vsp mRNAs and VSP proteins. Arabidopsis contains two vsp genes and real-time quantitative PCR allowed us to characterize their differential expression. The ratio of vsp1 to vsp2 mRNA abundance increased when plants were challenged with diamondback moth larvae or Egyptian cotton worms, but not when they were mechanically wounded. We observed a dramatic increase of vsp1 and vsp2 mRNA as well as VSP protein levels in leaves that experienced herbivore damage. By contrast, there was a relatively minor increase of vsp mRNA and VSP protein levels in undamaged leaves of infested plants. These results clearly demonstrate that VSPs are part of the local plant response to herbivore attack. To obtain additional information on vsp regulation, we analysed a fusion of a soybean vspB promoter fragment to the β-glucuronidase gene in transgenic Arabidopsis plants. The vspB promoter responded to both jasmonate and herbivore treatments, suggesting that similar signals regulate its expression in both plant species.     

Global expression profiling of sulfur-starved Arabidopsis by DNA macroarray reveals the role of O-acetyl-l-serine as a general regulator of gene expression in response to sulfur nutrition

To investigate the changes in profiles of mRNA accumulation in response to sulfur deficiency, approximately 13 000 non-redundant Arabidopsis thaliana ESTs corresponding to approximately 9000 genes were analyzed using DNA macroarray. Three-week-old Arabidopsis plants grown on an agarose-solidified control medium were transferred to a sulfate-free medium and grown for 48 h for the analyses of sulfur-related metabolites and global gene expression profiles. Concentrations of sulfate, O-acetyl-l-serine (OAS), a positive regulator of sulfur deficiency-responsive genes, cysteine and glutathione (GSH) were determined. Plants transferred to sulfate-free media had reduced concentrations of sulfate and GSH, and OAS concentrations increased. Macroarray analysis revealed a number of genes, including APR2 and Sultr1;2, whose mRNA accumulation was increased by sulfur deficiency. Profiling was also carried out with plants treated with OAS under sulfate-sufficient condition. Scatter plot analysis revealed a positive correlation between the changes of expression levels by sulfur deficiency and by OAS treatment among the clones tested, suggesting that mRNA accumulation of a number of genes under sulfur deficiency is mainly controlled by OAS concentrations in tissues. It was also revealed that the sets of genes regulated under sulfur deficiency in leaves and roots differ considerably.