ABSTRACT
Light, auxin and brassinosteroid play important roles in plant growth and development. Genetic analysis has demonstrated complex interactions between their signaling pathways, but the gene regulatory mechanisms connecting these pathways are poorly understood. CYP72B1 and AUR3 are two important genes responsive to light, auxin and brassinosteroid at transcription level. To understand the regulation mechanism of the two genes, a new tool called OCMMat was developed for identifying cis-elements, OCMMat combines both the over-representation property of regulatory elements in co-expressed genes and the conservation property in orthologous genes, for the latter, it was estimated by an enrichment score of regulatory element in orthologous promoter sequences. Using this tool, 3 regulatory motifs shared by genes CYP72B1 and AUR3 were reported, motif GAGACA which is the same as a known cis-element AuxRE, motif AAGAAAAA containing the sequence of GT element and the third ATCATG which is a new one named EDIB element. The space and the order of AAGAAAAA and EDIB show the same pattern in promoters of both the co-expressed genes and the orthologs of CYP72B1. Based on the sequence analysis and the literature knowledge to date, a model was proposed for describing the transcriptional regulatory mechanism of CYP72B1 and AUR3 in response to light, auxin and brassinosteroid. The model presents how the signaling pathways of light, auxin and brassinosteroid are interplaying at gene transcription level. In response to light, the transcription factors GT factor and an unknown protein repress the expression of CYP72B1 and AUR3, the hormone pathways are not interfered and thus work in their own way. While in the absence of light stimulation, CYP72B1 and AUR3 are expressed and the products, in turn, inhibit both the auxin pathway and the brassinosteroid pathways. On the other side, at high hormone level, gene expression is up-regulated through ARF binding, the gene products inhibit the hormone pathways in a feedback manner, and meanwhile, rescues the light signal through the photoreceptor phyB.
ABSTRACT
In order to explore the role of activator protein-1 (AP-1) in the transcription of interleukin-5 (IL-5) gene regulated by protein kinase C (PKC) signal in peripheral blood T lymphocytes from asthmatic patient, T lymphocytes were isolated and purified from peripheral blood of each asthmatic patient. The T lymphocytes were randomly divided int9 4 groups: group A (blank control), group B (treated with PKC agonist phorbol 12-myristate 13-acetate (PMA)), Group C (treated with PMA and AP-1 cis-element decoy oligodeoxynucleotides (decoy ODNs)), and group D (treated with PMA and AP-1 mutant decoy ODNs). The ODNs were transfected into the T cells of group C and D by cation liposome respectively. Reverse transcription-polymerase chain reaction (RT-PCR) was employed to assess IL-5 mRNA expression, and electrophoretic mobility shift assays (EMSA) for the activation of AP-1. The results showed that the activation of AP-1 (88 003.58±1 626.57) and the expression of IL5 mRNA (0. 8300±0. 0294) in T lymphocytes stimulated with PMA were significantly higher than these in blank control (20 888.47±1103.56 and 0. 3050±0. 0208, respectively, P＜ 0.01), while the indexes (23 219.83±1 024.86 and 0. 3425±0. 0171 respectively) of T lymphocytes stimulated with PMA and AP-1 decoy ODNs were significantly inhibited, as compared with group B (P＜0.01). The indexes (87 107. 41±1 342.92 and 0. 8225±0. 0222, respectively) in T lymphocytes stimulated with PMA and AP-1 mutant decoy ODNs did not exhibit significant changes, as compared with group B (P＞0.05). The significant positive correlation was found between the activation of AP-1 and the expression of IL-5 mRNA (P＜ 0.01). It was concluded that AP-1 might participate in the signal transduction of PKC-triggered transcription of IL-5 gene in asthmatic T lymphocytes. This suggests the activation of PKC/AP-1 signal transduction cascade of T lymphocytes may play an important role in the pathogenesis of asthma.
ABSTRACT
A novel radish RsPHGPx cDNA, which encodes a functional phospholipid hydroperoxide glutathioneperoxidase (PHGPx) protein, was identified in the previous work. In the study genomic organization and the upstream regulatory sequence analysis of this gene was presented. Southern blot analysis showed that RsPHGPx gene existed in radish genome in manner of single copy. Moreover, a 3.3 kb genomic DNA fragment of RsPHGPx gene was isolated by combination of common PCR and genome-walking method. Sequence analysis on this genomic fragment demonstrated that RsPHGPx gene consists of seven exons separated by six introns, and suggested that a short 5'-flanking sequence immediately before the exon 1 should be the putative RsPHGPx promoter region, which is proceeded by the upstream neighboring biotin synthase gene. Cis-acting elements search showed that the putative promoter contains elements responsive to hormones (eg. E-Box and W-Box), abiotic stresses (eg. MYB and MYC binding sites), and light (Box Ⅱ and Ⅰ-Box), etc. Northern blot analysis indicated that the expression of RsPHGPx was subjected to up-regulation of chilling and down-regulation of ABA and successive illumination (in etiolated seedlings), implying the regulatory roles of some predicted elements. However the up-regulation effect of herbicide paraquat, which can induce oxidative stress, suggested the presence of some unknown elements in the promoter region. This is the first report on gene structure and upstream regulatory sequence analysis in reported plant PHGPx genes, which will be a prerequisite to understand regulatory mechanism of PHGPx gene expression in plants.