UVR8 Interacts with BES1 and BIM1 to Regulate Transcription and Photomorphogenesis in Arabidopsis

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拟南芥根特异表达基因启动子在烟草中的表达

以拟南芥为材料,利用PCR技术分离pyk10启动子序列,构建了该启动子GUS植物表达载体,农杆菌介导转化烟草,分析该基因在烟草中的表达,以明确拟南芥根特异表达基因pyk10启动子在烟草中的表达特性.结果表明:克隆的pyk10启动子与已报道的pyk10启动子一致性为100%,GUS基因在烟草的根部特异表达,表明该启动子为根部特异表达启动子,为揭示植物根的发生、分化和发育机制,以及培育抗根部病虫害和营养高效利用型转基因烟草奠定了基础.     

Two Novel Src Homology 2 Domain Proteins Interact to Regulate Dictyostelium Gene Expression during Growth and Early Development

There are 13 Dictyostelium Src homology 2 (SH2) domain proteins, almost 10-fold fewer than in mammals, and only three are functionally unassigned. One of these, LrrB, contains a novel combination of protein interaction domains: an SH2 domain and a leucine-rich repeat domain. Growth and early development appear normal in the mutant, but expression profiling reveals that three genes active at these stages are greatly underexpressed: the ttdA metallohydrolase, the abcG10 small molecule transporter, and the cinB esterase. In contrast, the multigene family encoding the lectin discoidin 1 is overexpressed in the disruptant strain. LrrB binds to 14-3-3 protein, and the level of binding is highest during growth and decreases during early development. Comparative tandem affinity purification tagging shows that LrrB also interacts, via its SH2 domain and in a tyrosine phosphorylation-dependent manner, with two novel proteins: CldA and CldB. Both of these proteins contain a Clu domain, a >200-amino acid sequence present within highly conserved eukaryotic proteins required for correct mitochondrial dispersal. A functional interaction of LrrB with CldA is supported by the fact that a cldA disruptant mutant also underexpresses ttdA, abcG10, and cinB. Significantly, CldA is itself one of the three functionally unassigned SH2 domain proteins. Thus, just as in metazoa, but on a vastly reduced numerical scale, an interacting network of SH2 domain proteins regulates specific Dictyostelium gene expression.     

HY5 and ABI5 transcription factors physically interact to fine tune light and ABA signaling in Arabidopsis

Plant Molecular Biology - Cross-talk between light and ABA signaling is mediated by physical interaction between HY5 and ABI5 Arabidopsis. Plants undergo numerous transitions during their...     

ABA-INSENSITIVE3, ABA-INSENSITIVE5, and DELLAs Interact to Activate the Expression of SOMNUS and Other High-Temperature-Inducible Genes in Imbibed Seeds in Arabidopsis

Seeds monitor the environment to germinate at the proper time, but different species respond differently to environmental conditions, particularly light and temperature. In Arabidopsis thaliana, light promotes germination but high temperature suppresses germination. We previously reported that light promotes germination by repressing SOMNUS (SOM). Here, we examined whether high temperature also regulates germination through SOM and found that high temperature activates SOM expression. Consistent with this, som mutants germinated more frequently than the wild type at high temperature. The induction of SOM mRNA at high temperature required abscisic acid (ABA) and gibberellic acid biosynthesis, and ABA-INSENSITIVE3 (ABI3), ABI5, and DELLAs positively regulated SOM expression. Chromatin immunoprecipitation assays indicated that ABI3, ABI5, and DELLAs all target the SOM promoter. At the protein level, ABI3, ABI5, and DELLAs all interact with each other, suggesting that they form a complex on the SOM promoter to activate SOM expression at high temperature. We found that high-temperature-inducible genes frequently have RY motifs and ABA-responsive elements in their promoters, some of which are targeted by ABI3, ABI5, and DELLAs in vivo. Taken together, our data indicate that ABI3, ABI5, and DELLAs mediate high-temperature signaling to activate the expression of SOM and other high-temperature-inducible genes, thereby inhibiting seed germination.     

Gemin5 Binds to the Survival Motor Neuron mRNA to Regulate SMN Expression

Reduced expression of SMN causes spinal muscular atrophy, a severe neurodegenerative disease. Despite the importance of maintaining SMN levels, relatively little is known about the mechanisms by which SMN levels are regulated. We show here that Gemin5, the snRNA-binding protein of the SMN complex, binds directly to the SMN mRNA and regulates SMN expression. Gemin5 binds with high specificity, both in vitro and in vivo, to sequence and structural elements in the SMN mRNA 3′-untranslated region that are reminiscent of the snRNP code to which Gemin5 binds on snRNAs. Reduction of Gemin5 redistributes the SMN mRNA from heavy polysomes to lighter polysomes and monosomes, suggesting that Gemin5 functions as an activator of SMN translation. SMN protein is not stoichiometrically present on the SMN mRNA with Gemin5, but the mRNA-binding activity of Gemin5 is dependent on SMN levels, providing a feedback mechanism for SMN to regulate its own expression via Gemin5. This work both reveals a new autoregulatory pathway governing SMN expression, and identifies a new mechanism through which SMN can modulate specific mRNA expression via Gemin5.     

HY5-HDA9 orchestrates the transcription of HsfA2 to modulate salt stress response in Arabidopsis

Integration of light signaling and diverse abiotic stress responses contribute to plant survival in a changing environment. Some reports have indicated that light signals contribute a plant's ability to deal with heat, cold, and stress. However, the molecular link between light signaling and the salt-response pathways remains unclear. We demonstrate here that increasing light intensity elevates the salt stress tolerance of plants. Depletion of HY5, a key component of light signaling, causes Arabidopsis thaliana to become salinity sensitive. Interestingly, the small heat shock protein (sHsp) family genes are upregulated in hy5-215 mutant plants, and HsfA2 is commonly involved in the regulation of these sHsps. We found that HY5 directly binds to the G-box motifs in the HsfA2 promoter, with the cooperation of HISTONE DEACETYLASE 9 (HDA9), to repress its expression. Furthermore, the accumulation of HDA9 and the interaction between HY5 and HDA9 are significantly enhanced by salt stress. On the contrary, high temperature triggers HY5 and HDA9 degradation, which leads to dissociation of HY5-HDA9 from the HsfA2 promoter, thereby reducing salt tolerance. Under salt and heat stress conditions, fine tuning of protein accumulation and an interaction between HY5 and HDA9 regulate HsfA2 expression. This implies that HY5, HDA9, and HsfA2 play important roles in the integration of light signaling with salt stress and heat shock response.     

Use of the Lactococcal nisA Promoter To Regulate Gene Expression in Gram-Positive Bacteria: Comparison of Induction Level and Promoter Strength

We characterized the regulated activity of the lactococcal nisA promoter in strains of the gram-positive species Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus pneumoniae, Enterococcus faecalis, and Bacillus subtilis. nisA promoter activity was dependent on the proteins NisR and NisK, which constitute a two-component signal transduction system that responds to the extracellular inducer nisin. The nisin sensitivity and inducer concentration required for maximal induction varied among the strains. Significant induction of the nisA promoter (10- to 60-fold induction) was obtained in all of the species studied at a nisin concentration just below the concentration at which growth is inhibited. The efficiency of the nisA promoter was compared to the efficiencies of the Spac, xylA, and lacA promoters in B. subtilis and in S. pyogenes. Because nisA promoter-driven expression is regulated in many gram-positive bacteria, we expect it to be useful for genetic studies, especially studies with pathogenic streptococci in which no other regulated promoters have been described.