Abstract
Phenolic acids are the main active ingredients in Salvia miltiorrhiza, which can be used for the treatment of many diseases, particularly cardiovascular diseases. It is known that salicylic ...acid (SA) can enhance phenolic acid content, but the molecular mechanism of its regulation is still unclear. Nonexpresser of PR genes 1 (NPR1) plays a positive role in the SA signaling pathway. In this study, we identified a SmNPR1 gene that responds to SA induction and systematically investigated its function. We found that SmNPR1 positively affected phenolic acid biosynthesis. Then, we identified a novel TGA transcription factor, SmTGA2, which interacts with SmNPR1. SmTGA2 positively regulates phenolic acid biosynthesis by directly up-regulating SmCYP98A14 expression. After double-gene transgenic analysis and other biochemical assays, it was found that SmNPR1 and SmTGA2 work synergistically to regulate phenolic acid biosynthesis. In addition, SmNPR4 forms a heterodimer with SmNPR1 to inhibit the function of SmNPR1, and SA can alleviate this effect. Collectively, these findings elucidate the molecular mechanism underlying the regulation of phenolic acid biosynthesis by SmNPR1–SmTGA2/SmNPR4 modules and provide novel insights into the SA signaling pathway regulating plant secondary metabolism.
SmNPR1, a key protein in the salicylic acid signaling pathway, dynamically regulates salicylic acid-induced phenolic acid biosynthesis in Salvia miltiorrhizaby interacting with SmNPR4 and the transcription factor SmTGA2.
Arabidopsis TGA class II transcription factors are part of a signaling network that controls ROS levels and oxidative damage in the tolerance response to UV-B and photooxidative stress.
Abstract
...Plants possess a robust metabolic network for sensing and controlling reactive oxygen species (ROS) levels upon stress conditions. Evidence shown here supports a role for TGA class II transcription factors as critical regulators of genes controlling ROS levels in the tolerance response to UV-B stress in Arabidopsis. First, tga256 mutant plants showed reduced capacity to scavenge H2O2 and restrict oxidative damage in response to UV-B, and also to methylviologen-induced photooxidative stress. The TGA2 transgene (tga256/TGA2 plants) complemented these phenotypes. Second, RNAseq followed by clustering and Gene Ontology term analyses indicate that TGA2/5/6 positively control the UV-B-induced expression of a group of genes with oxidoreductase, glutathione transferase, and glucosyltransferase activities, such as members of the glutathione S-transferase Tau subfamily (GSTU), which encodes peroxide-scavenging enzymes. Accordingly, increased glutathione peroxidase activity triggered by UV-B was impaired in tga256 mutants. Third, the function of TGA2/5/6 as transcriptional activators of GSTU genes in the UV-B response was confirmed for GSTU7, GSTU8, and GSTU25, using quantitative reverse transcription–PCR and ChIP analyses. Fourth, expression of the GSTU7 transgene complemented the UV-B-susceptible phenotype of tga256 mutant plants. Together, this evidence indicates that TGA2/5/6 factors are key regulators of the antioxidant/detoxifying response to an abiotic stress such as UV-B light overexposure.
Soybean (Glycine max) infection by the charcoal rot (CR) ascomycete Macrophomina phaseolina is enhanced by the soybean cyst nematode (SCN) Heterodera glycines. We hypothesized that G. max genetic ...lines impairing infection by M. phaseolina would also limit H. glycines parasitism, leading to resistance. As a part of this M. phaseolina resistance process, the genetic line would express defense genes already proven to impair nematode parasitism. Using G. maxDT97-4290/PI 642055, exhibiting partial resistance to M. phaseolina, experiments show the genetic line also impairs H. glycines parasitism. Furthermore, comparative studies show G. maxDT97-4290/PI 642055 exhibits induced expression of the effector triggered immunity (ETI) gene NON-RACE SPECIFIC DISEASE RESISTANCE 1/HARPIN INDUCED1 (NDR1/HIN1) that functions in defense to H. glycines as compared to the H. glycines and M. phaseolina susceptible line G. maxWilliams 82/PI 518671. Other defense genes that are induced in G. maxDT97-4290/PI 642055 include the pathogen associated molecular pattern (PAMP) triggered immunity (PTI) genes ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1), NONEXPRESSOR OF PR1 (NPR1) and TGA2. These observations link G. max defense processes that impede H. glycines parasitism to also potentially function toward impairing M. phaseolina pathogenicity. Testing this hypothesis, G. maxWilliams 82/PI 518671 genetically engineered to experimentally induce GmNDR1-1, EDS1-2, NPR1-2 and TGA2-1 expression leads to impaired M. phaseolina pathogenicity. In contrast, G. maxDT97-4290/PI 642055 engineered to experimentally suppress the expression of GmNDR1-1, EDS1-2, NPR1-2 and TGA2-1 by RNA interference (RNAi) enhances M. phaseolina pathogenicity. The results show components of PTI and ETI impair both nematode and M. phaseolina pathogenicity.
•G. maxDT97-4290/PI 642055, partially Macrophomina phaseolina resistant also exhibits Heterodera glycines resistance.•Higher levels of NDR1/HIN1, EDS1 and TGA2 exist in G. maxDT97-4290/PI 642055, compared to controls.•Soybean NDR1, EDS1, NPR1 and TGA2 suppress M. phaseolina infection.•The bacterial effector harpin activates a defense response to M. phaseolina in soybean.
The Arabidopsis NPR1 gene is essential in activating systemic, inducible plant defense responses. To gain a better understanding of NPR1 function, we conducted a yeast two-hybrid screening procedure ...and identified a differential interaction between NPR1 and all known members of the Arabidopsis TGA family of basic leucine zipper transcription factors. In the electrophoretic mobility shift assay, NPR1 substantially increased the binding of TGA2 to its cognate promoter element (as-1) as well as to a positive salicylic acid-inducible element (LS7) and a negative element (LS5) in the promoter of the pathogenesis-related PR-1 gene. Proteins encoded by npr1 mutants interacted poorly with TGA2 and did not substantially increase TGA2 binding to the as-1, LS5, or LS7 elements, thus establishing a link between the loss of disease resistance and the loss of TGA2 interaction and NPR1-enhanced DNA binding. Coupled with observations that the DNA binding activity of TGA factors is deregulated in npr1 plants, the results suggest that NPR1-mediated DNA binding of TGA2 is critical for activation of defense genes.
AIM： To evaluate the impact of the ITGA2 gene polymorphism on gastric cancer risk. METHODS： A hospital-based case-control study was conducted, including 307 gastric cancer patients and 307 age- and ...gender-matched control subjects. The genotypes were identified by polymerase chain reaction-restriction fragment length polymorphism assay. RESULTS： The frequencies of the wild and variant genotypes in cases were significantly different from those of controls （P = 0.019）. Compared with individuals with the wild genotype CC, subjects with the variant genotypes （CT ＋ IT） had a significantly higher risk of gastric cancer （adjusted odds ratio = 1.57, 95% CI = 1.13-2.17, P = 0.007）. In stratified analyses, the elevated gastric cancer risk was especially evident in older individuals aged 〉 58 years, nonsmokers and rural subjects. Further analyses revealed that the variant genotypes were associated with poor tumor differentiation and adjacent organ invasion in the sub-analysis of gastric cancer patients. CONCLUSION： The ITGA2 gene C807T polymorphism may be associated with an increased risk of gastric cancer, differentiation and invasion of gastric cancer.
Summary
The Arabidopsis thaliana NIM1/NPR1 gene product is required for induction of systemic acquired resistance (SAR) by pathogens, salicylic acid (SA) or synthetic SA analogs. We identified, in a ...yeast two‐hybrid screen, two NIM1/NPR1 interacting proteins, TGA2 and TGA5, which belong to the basic region, leucine zipper (bZIP) family of transcription factors. Both TGA2 and TGA5 strongly interact with NIM1/NPR1 in yeast and in vitro, and recognize the as‐1 cis element found within the promoter of several pathogenesis‐related genes, such as PR‐1. To determine the role TGA2 and TGA5 may play in NIM1/NPR1‐mediated disease resistance, we introduced sense and antisense versions of both genes into transgenic Arabidopsis plants. Characterization of TGA2 transgenic plants revealed that inhibition or overexpression of TGA2 does not significantly affect PR‐1 expression or induction of SAR after pathogen infection or INA treatment. Surprisingly, all TGA5‐antisense transgenic plants produced showed increased accumulation of TGA5 transcripts compared with untransformed control plants, while the TGA5‐sense lines showed no significant increase in TGA5 mRNA levels. Interestingly, the high level of TGA5 mRNA in the antisense lines was accompanied by significant resistance to a highly virulent isolate of the oomycete pathogen Peronospora parasitica. Further, resistance was not coupled to accumulation of products from the SAR‐linked PR‐1 gene following inoculation with P. parasitica or treatment with INA, indicating that these plants express a robust, PR‐1‐independent resistance mechanism. Resistance was retained when a TGA5‐accumulating line was combined genetically with a nim1‐1 mutation or nahG (salicylate hydroxylase) transgene, indicating that resistance in these plants is due to an SA and SAR‐independent mechanism.
The protein NPR1/NIM1 is required for the induction of systemic acquired resistance (SAR) in plants and has been shown to interact with members of the TGA/OBF family of basic leucine zipper (bZIP) ...transcription factors. However, to date, there is no method available to monitor such interactions in plant cells. We report here an in vivo protein fragment complementation assay (PCA), based on association of reconstituted murine dihydrofolate reductase (mDHFR) with a fluorescent probe to detect protein-protein interaction in planta. We demonstrate that the interaction between Arabidopsis NPR1/NIM1 and the bZIP factor TGA2 is induced by the regulators of SAR, salicylic acid (SA), and its analog 2,6-dichloroisonicotinic acid (INA) with distinct species-specific responses. Furthermore, the induced interaction is localized predominantly in the nucleus. Protein fragment complementation assays could be of value to agricultural research by providing a system for high-throughput biochemical pathway mapping and for screening of small molecules that modulate protein interactions.
Much of what we, as plant molecular biologists studying gene regulation, know comes from paradigms characterized or developed in mammalian systems. Although plants, animals, and fungi have been ...diverging for a very long time, a great deal of the machineries and components discovered in yeast and mammals seem to have been maintained in plants. Nevertheless, despite this apparent conservation, evolutionary pressures on the mechanisms of gene regulation are likely to be different between these kingdoms, given their different environmental constraints. As such, it is imperative for plant molecular biologists to develop their own paradigms, even on seemingly conserved systems. It is with this intent that we compare and contrast the regulation of two pathogenesis-related genes, the arabidopsis PR-1 and potato PR-10a genes. The transcription factors regulating these genes present prime paradigms for the study of plant signal- and context-dependent dual-function transcription factors.
Systemic acquired resistance (SAR) is triggered by hormone defense cues and is associated with the onset of expression of pathogenesis-related (PR) genes that encode for anti-microbial proteins in ...plants. In the case of
PR-1, transcriptional activation involves promoter-specific recruitment of transcription factors such as TGA2 through a mechanism that may involve transient physical interaction with the NPR1 protein. This stimulus-inducible recruitment process has yet to be fully explained at the functional and mechanistic level. To investigate this question further, we initially looked to see whether NPR1 preferentially forms a complex with the DNA bound or unbound fraction of TGA2. As shown here, NPR1 appears to preferentially interact with the non-DNA bound fraction of TGA2. We subsequently mutated this transcription factor to identify key residues in its conserved carboxyl terminal (CT) domain that mediate complex formation with NPR1. These approaches revealed that two non-overlapping regions of the CT domain of TGA2 bind independently to NPR1. The specificity and biological significance of these findings were inferred with a mutant form of NPR1 that fails to activate SAR
in vivo. These and other findings raise the possibility that NPR1 may transiently interact with the DNA unbound fraction of TGA2 to promote its recruitment to an active form on cognate target promoters.
A major challenge in modern biology is the visualization of biochemical pathways in living cells. Subramaniam
et al. report on the application of a new technology called ‘protein fragment ...complementation assays’ (PCAs), which is used to visualize a key step in a signal transduction pathway underlying systemic acquired resistance in higher-plant cells. Their results suggest a wide range of potential applications of their strategy in visualizing biochemical processes and in determining gene function.
Subramaniam et al report a new technology ‘protein fragment complementation assays’ (PCAs), which can be used to visulize a key step in a signal transduction pathway.
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