1,135 Genomes Reveal the Global Pattern of Polymorphism in Arabidopsis thaliana

骨髄異形成症候群のgenome-wide analysis

Transcription factors belonging to the APETALA2/Ethylene Responsive Factor (AP2/ERF) family are conservatively widespread in the plant kingdom. These regulatory proteins are involved in the control of primary and secondary metabolism, growth and developmental programs, as well as responses to environmental stimuli. Due to their plasticity and to the specificity of individual members of this family, AP2/ERF transcription factors represent valuable targets for genetic engineering and breeding of crops. In this review, we integrate the evidence collected from functional and structural studies to describe their different mechanisms of action and the regulatory pathways that affect their activity.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/nph.12291

APETALA2/Ethylene Responsive Factor (AP2/ERF) transcription factors: mediators of stress responses and developmental programs

ABA-dependent and ABA-independent signaling in response to osmotic stress in plants

Drought negatively impacts plant growth and the productivity of crops around the world. Understanding the molecular mechanisms in the drought response is important for improvement of drought tolerance using molecular techniques. In plants, abscisic acid (ABA) is accumulated under osmotic stress conditions caused by drought, and has a key role in stress responses and tolerance. Comprehensive molecular analyses have shown that ABA regulates the expression of many genes under osmotic stress conditions, and the ABA-responsive element (ABRE) is the major cis-element for ABA-responsive gene expression. Transcription factors (TFs) are master regulators of gene expression. ABRE-binding protein and ABRE-binding factor TFs control gene expression in an ABA-dependent manner. SNF1-related protein kinases 2, group A 2C-type protein phosphatases, and ABA receptors were shown to control the ABA signaling pathway. ABA-independent signaling pathways such as dehydration-responsive element-binding protein TFs and NAC TFs are also involved in stress responses including drought, heat, and cold. Recent studies have suggested that there are interactions between the major ABA signaling pathway and other signaling factors in stress responses. The important roles of these TFs in crosstalk among abiotic stress responses will be discussed. Control of ABA or stress signaling factor expression can improve tolerance to environmental stresses. Recent studies using crops have shown that stress-specific overexpression of TFs improves drought tolerance and grain yield compared with controls in the field.

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The transcriptional regulatory network in the drought response and its crosstalk in abiotic stress responses including drought, cold, and heat

ETHYLENE RESPONSE FACTOR1 (ERF1) is an upstream component in both jasmonate (JA) and ethylene (ET) signaling and is involved in pathogen resistance. Accumulating evidence suggests that ERF1 might be related to the salt stress response through ethylene signaling. However, the specific role of ERF1 in abiotic stress and the molecular mechanism underlying the signaling cross talk still need to be elucidated. Here, we report that ERF1 was highly induced by high salinity and drought stress in Arabidopsis (Arabidopsis thaliana). The salt stress induction required both JA and ET signaling but was inhibited by abscisic acid. ERF1-overexpressing lines (35S:ERF1) were more tolerant to drought and salt stress. They also displayed constitutively smaller stomatal aperture and less transpirational water loss. Surprisingly, 35S:ERF1 also showed enhanced heat tolerance and up-regulation of heat tolerance genes compared with the wild type. Several suites of genes activated by JA, drought, salt, and heat were found in microarray analysis of 35S:ERF1. Chromatin immunoprecipitation assays found that ERF1 up-regulates specific suites of genes in response to different abiotic stresses by stress-specific binding to GCC or DRE/CRT. In response to biotic stress, ERF1 bound to GCC boxes but not DRE elements; conversely, under abiotic stress, we observed specific binding of ERF1 to DRE elements. Furthermore, ERF1 bound preferentially to only one among several GCC box or DRE/CRT elements in the promoter region of its target genes. ERF1 plays a positive role in salt, drought, and heat stress tolerance by stress-specific gene regulation, which integrates JA, ET, and abscisic acid signals.

/pdf/the-arabidopsis-ethylene-response-factor1-regulates-abiotic-ws0ckc5vkw.pdf

The Arabidopsis ETHYLENE RESPONSE FACTOR1 Regulates Abiotic Stress-Responsive Gene Expression by Binding to Different cis-Acting Elements in Response to Different Stress Signals

Transcriptional activities of plants play important roles in responses to environmental stresses. ETHYLENE RESPONSE FACTOR53 (AtERF53) is a drought-induced transcription factor that belongs to the AP2/ERF superfamily and has a highly conserved AP2 domain. It can regulate drought-responsive gene expression by binding to the GCC box and/or the dehydration-responsive element in the promoter of downstream genes. Overexpression of AtERF53 driven by the cauliflower mosaic virus 35S promoter resulted in an unstable drought-tolerant phenotype in T2 transgenic Arabidopsis (Arabidopsis thaliana) plants. Using a yeast two-hybrid screen, we identified a RING domain ubiquitin E3 ligase, RGLG2, which interacts with AtERF53 in the nucleus. The copine domain of RGLG2 exhibited the strongest interacting activity. We also demonstrated that RGLG2 could move from the plasma membrane to the nucleus under stress treatment. Using an in vitro ubiquitination assay, RGLG2 and its closest sequelog, RGLG1, were shown to have E3 ligase activity and mediated AtERF53 ubiquitination for proteasome degradation. The rglg1rglg2 double mutant but not the rglg2 or rglg1 single mutant exhibited a drought-tolerant phenotype when compared with wild-type plants. AtERF53-green fluorescent proteins expressed in the rglg1rglg2 double mutants were stable. The 35S:AtERF53-green fluorescent protein/rglg1rglg2 showed enhanced AtERF53-regulated gene expression and had greater tolerance to drought stress than the rglg1rglg2 double mutant. In conclusion, RGLG2 negatively regulates the drought stress response by mediating AtERF53 transcriptional activity in Arabidopsis.

/pdf/arabidopsis-rglg2-functioning-as-a-ring-e3-ligase-interacts-6wpas0lyqe.pdf

Arabidopsis RGLG2, Functioning as a RING E3 Ligase, Interacts with AtERF53 and Negatively Regulates the Plant Drought Stress Response

SUMMARY Although glutathione is well known for its reactive oxygen species (ROS) scavenging function and plays a protective role in biotic stress, its regulatory function in abiotic stress still remains to be elucidated. Our previous study showed that exogenously applied reduced glutathione (GSH) could improve abiotic stress tolerance in Arabidopsis. Here, we report that endogenously increased GSH also conferred tolerance to drought and salt stress in Arabidopsis. Moreover, both exogenous and endogenous GSH delayed senescence and flowering time. Polysomal profiling results showed that global translation was enhanced after GSH treatment and by the induced increase of GSH level by salt stress. By performing transcriptomic analyses of steady-state and polysome-bound mRNAs in GSH-treated plants, we reveal that GSH has a substantial impact on translation. Translational changes induced by GSH treatment target numerous hormones and stress signaling molecules, which might contribute to the enhanced stress tolerance in GSH-treated plants. Our translatome analysis also revealed that abscisic acid (ABA), auxin and jasmonic acid (JA) biosynthesis, as well as signaling genes, were activated during GSH treatment, which has not been reported in previously published transcriptomic data. Together, our data suggest that the increased glutathione level results in stress tolerance and global translational changes.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/tpj.12940

Increased glutathione contributes to stress tolerance and global translational changes in Arabidopsis

ORA47 (octadecanoid-responsive AP2/ERF-domain transcription factor 47) of Arabidopsis thaliana is an AP2/ERF domain transcription factor that regulates jasmonate (JA) biosynthesis and is induced by methyl JA treatment. The regulatory mechanism of ORA47 remains unclear. ORA47 is shown to bind to the cis-element (NC/GT)CGNCCA, which is referred to as the O-box, in the promoter of ABI2. We proposed that ORA47 acts as a connection between ABA INSENSITIVE1 (ABI1) and ABI2 and mediates an ABI1-ORA47-ABI2 positive feedback loop. PORA47:ORA47-GFP transgenic plants were used in a chromatin immunoprecipitation (ChIP) assay to show that ORA47 participates in the biosynthesis and/or signaling pathways of nine phytohormones. Specifically, many abscisic acid (ABA) and JA biosynthesis and signaling genes were direct targets of ORA47 under stress conditions. The JA content of the P35S:ORA47-GR lines was highly induced under wounding and moderately induced under water stress relative to that of the wild-type plants. The wounding treatment moderately increased ABA accumulation in the transgenic lines, whereas the water stress treatment repressed the ABA content. ORA47 is proposed to play a role in the biosynthesis of JA and ABA and in regulating the biosynthesis and/or signaling of a suite of phytohormone genes when plants are subjected to wounding and water stress.

https://nph.onlinelibrary.wiley.com/doi/epdf/10.1111/nph.13914

ORA47 (octadecanoid-responsive AP2/ERF-domain transcription factor 47) regulates jasmonic acid and abscisic acid biosynthesis and signaling through binding to a novel cis-element

AP2/ERF proteins play crucial roles in plant growth and development and in responses to biotic and abiotic stresses. ETHYLENE RESPONSE FACTOR 53 (AtERF53) belongs to group 1 in the ERF family and is induced in the early hours of dehydration and salt treatment. The functional study of AtERF53 is hampered because its protein expression in Arabidopsis is vulnerable to degradation in overexpressed transgenic lines. Taking advantage of the RING domain ligase1/RING domain ligase2 (rglg1rglg2) double mutant in which the AtERF53 can express stably, we investigate the physiological function of AtERF53. In this study, we demonstrate that expression of AtERF53 in wild-type Arabidopsis was responsive to heat and abscisic acid (ABA) treatment. From results of the cotransfection experiment, we concluded that AtERF53 has positive transactivation activity. Overexpression of AtERF53 in the rglg1rglg2 double mutant conferred better heat-stress tolerance and had resulted in higher endogenous ABA and proline levels compared to rglg1rglg2 double mutants. AtERF53 also has a function to regulate guard-cell movement because the stomatal aperture of AtERF53 overexpressed in rglg1rglg2 double mutant was smaller than that in the rglg1rglg2 double mutant under ABA treatment. In a global gene expression study, we found higher expressions of many stress-related genes, such as DREB1A, COR15A, COR15B, PLC, P5CS1,
 cpHSC70 s and proline and ABA metabolic-related genes. Furthermore, we identified several downstream target genes of AtERF53 by chromatin immunoprecipitation assay. In conclusion, the genetic, molecular and biochemical result might explain how AtERF53 serving as a transcription factor contributes to abiotic stress tolerance in Arabidopsis.

Mei-Chun Cheng

Papers

The Arabidopsis ETHYLENE RESPONSE FACTOR1 Regulates Abiotic Stress-Responsive Gene Expression by Binding to Different cis-Acting Elements in Response to Different Stress Signals

Arabidopsis RGLG2, Functioning as a RING E3 Ligase, Interacts with AtERF53 and Negatively Regulates the Plant Drought Stress Response

Increased glutathione contributes to stress tolerance and global translational changes in Arabidopsis

ORA47 (octadecanoid-responsive AP2/ERF-domain transcription factor 47) regulates jasmonic acid and abscisic acid biosynthesis and signaling through binding to a novel cis-element

Functional characterization of an abiotic stress-inducible transcription factor AtERF53 in Arabidopsis thaliana