Ethylene Response Factor Genes Research Articles

A group VII ethylene response factor gene, ZmEREB180, coordinates waterlogging tolerance in maize seedlings.

SummaryGroup VII ethylene response factors (ERFVIIs) play important roles in ethylene signalling and plant responses to flooding. However, natural ERFVII variations in maize (ZmERFVIIs) that are directly associated with waterlogging tolerance have not been reported. Here, a candidate gene association analysis of the ZmERFVII gene family showed that a waterlogging‐responsive gene, ZmEREB180, was tightly associated with waterlogging tolerance. ZmEREB180 expression specifically responded to waterlogging and was up‐regulated by ethylene; in addition, its gene product localized to the nucleus. Variations in the 5ʹ‐untranslated region (5ʹ‐UTR) and mRNA abundance of this gene under waterlogging conditions were significantly associated with survival rate (SR). Ectopic expression of ZmEREB180 in Arabidopsis increased the SR after submergence stress, and overexpression of ZmEREB180 in maize also enhanced the SR after long‐term waterlogging stress, apparently through enhanced formation of adventitious roots (ARs) and regulation of antioxidant levels. Transcriptomic assays of the transgenic maize line under normal and waterlogged conditions further provided evidence that ZmEREB180 regulated AR development and reactive oxygen species homeostasis. Our study provides direct evidence that a ZmERFVII gene is involved in waterlogging tolerance. These findings could be applied directly to breed waterlogging‐tolerant maize cultivars and improve our understanding of waterlogging stress.

In silico and Expression Profile Analyses of the ERF Subfamily in Melon

Ethylene-responsive factors (ERFs) are a subfamily of the AP2/ERF superfamily and a group of plant-specific transcription factors involved in many plant growth and development regulatory processes. However, few information about the function of ERFs in melon. To identify ERFs that may play a role in the growth and development of melon, using bioinformatics, we investigated their physicochemical properties, subcellular localization, signal peptides, promoter elements, and chromosomal location. Eighty-three promoter elements were predicted at 1500 bp upstream of their related genes. The chromosomal results suggested 64 ERFs are distributed among 12 chromosomes. On the basis of a multiple sequence alignment, phylogenetic analysis was conducted for all the ERF proteins in melon, arabidopsis (Arabidopsis thaliana) and tomato. Nine distinct groups were identified, and melon ERFs occurred within eight clades. Furthermore, the expression profiles of the genes in different tissues were investigated using quantitative real-time PCR (qRT-PCR). The results showed that 63, 57, and 54 ERF genes were expressed in distinct vegetative organs, fruits at different days after pollination (DAP), and fruits during the respiratory climacteric, respectively. Among those genes, CmERFIII-1 which was a valuable gene for studying its function in melon exhibited the highest expression in different tissues. Another very interesting gene was CmERFIV-2, which was the only gene whose expression was the highest in root in all highly expressed genes. Furthermore, four genes from the fourth subset (CmERFIV-2, IV-3, IV-4 and IV-5) were highly expressed in fruits at different developmental stages. Together, these results will aid future functional analysis of these genes.

High-CO2/Hypoxia-Responsive Transcription Factors DkERF24 and DkWRKY1 Interact and Activate DkPDC2 Promoter.

Identification and functional characterization of hypoxia-responsive transcription factors is important for understanding plant responses to natural anaerobic environments and during storage and transport of fresh horticultural products. In this study, yeast one-hybrid library screening using the persimmon (Diospyros kaki) pyruvate decarboxylase (DkPDC2) promoter identified three ethylene response factor (ERF) genes (DkERF23/DkERF24/DkERF25) and four WRKY transcription factor genes (DkWRKY/DdkWRKY5/DkWRKY6/DkWRKY7) that were differentially expressed in response to high CO2 (95%, with 4% N2 and 1% oxygen) and high N2 (99% N2 and 1% oxygen). Yeast one-hybrid assays and electrophoretic mobility shift assays indicated that DkERF23, DkERF24, DkERF25, DkWRKY6, and DkWRKY7 could directly bind to the DkPDC2 promoter. Dual-luciferase assays confirmed that these transcription factors were capable of transactivating the DkPDC2 promoter. DkERF24 and DkWRKY1 in combination synergistically transactivated the DkPDC2 promoter, and yeast two-hybrid and bimolecular fluorescence complementation assays confirmed protein-protein interaction between DkERF24 and DkWRKY1. Transient overexpression of DkERF24 and DkWRKY1 separately and in combination in persimmon fruit discs was effective in maintaining insolubilization of tannins, concomitantly with the accumulation of DkPDC2 transcripts. Studies with Arabidopsis (Arabidopsis thaliana) homologs AtERF1 and AtWRKY53 indicated that similar protein-protein interactions and synergistic regulatory effects also occur with the DkPDC2 promoter. We propose that an ERF and WRKY transcription factor complex contributes to responses to hypoxia in both persimmon fruit and Arabidopsis, and the possibility that this is a general plant response requires further investigation.

HDA9-PWR-HOS15 Is a Core Histone Deacetylase Complex Regulating Transcription and Development.

Histone deacetylases remove acetyl groups from histone proteins and play important roles in many genomic processes. How histone deacetylases perform specialized molecular and biological functions in plants is poorly understood. Here, we identify HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 15 (HOS15) as a core member of the Arabidopsis (Arabidopsis thaliana) HISTONE DEACETYLASE9-POWERDRESS (HDA9-PWR) complex. HOS15 immunoprecipitates with both HDA9 and PWR. Mutation of HOS15 induces histone hyperacetylation and methylation changes similar to hda9 and pwr mutants. HOS15, HDA9, and PWR are coexpressed in all organs, and mutant combinations display remarkable phenotypic resemblance and nonadditivity for organogenesis and developmental phase transitions. Ninety percent of HOS15-regulated genes are also controlled by HDA9 and PWR HDA9 binds to and directly represses 92 genes, many of which are responsive to biotic and abiotic stimuli, including a family of ethylene response factor genes. Additionally, HOS15 regulates HDA9 nuclear accumulation and chromatin association. Collectively, this study establishes that HOS15 forms a core complex with HDA9 and PWR to control gene expression and plant development.

Constitutive expression of a stabilized transcription factor group VII ethylene response factor enhances waterlogging tolerance in wheat without penalizing grain yield.

Waterlogging causes oxygen deprivation within plant roots and affects crop growth and yield. In crop wheat (Triticum aestivum), molecular responses to waterlogging are poorly understood. Here, we performed a genome-wide analysis of group VII ethylene response factor (ERFVII) genes in hexaploid wheat and identified 25 genes, which were induced by waterlogging with diverse manner. Among them, TaERFVII.1 exhibited differential expression patterns between waterlogging-tolerant wheat Nonglin46 and susceptible wheat Yangmai16 under waterlogging. Constitutive expression of TaERFVII.1 with an MYC-peptide tag at its N terminus in wheat enhanced tolerance to waterlogging as evidenced by increased grain weight per plant, survival rate, and chlorophyll content of leaves and by increased expression of waterlogging-responsive genes, while silencing of TaERFVII.1 compromised the expression of waterlogging-responsive genes. Notably, constitutive expression of the stabilized TaERFVII.1 did not negatively impact both plant development and grain yield under standard conditions. We further demonstrated that constitutive expression of stabilized TaERFVII.1 elevated the transcriptional level of TaSAB18.1, the ortholog of Arabidopsis HRA1 and rice SAB18, consequently reduced the expression of waterlogging-responsive genes under standard conditions. These results suggest that TaERFVII.1 plays an important role in wheat tolerance to waterlogging, and it could be a candidate for improving crop waterlogging tolerance.

Effects of Vacuum Packaging on Enzymatic Browning and Ethylene Response Factor (ERF) Gene Expression of Fresh-cut Lotus Root

Ethylene response factor (ERF) genes have been involved in responses to biotic and abiotic stress, including hypoxia and anaerobic stress. Vacuum packaging (a typical anaerobic stress) is an effective storage method used to delay browning of fresh-cut lotus root (Nelumbo nucifera). In model plants, ERF genes have been identified as responsive to hypoxia. Whether ERF is associated with browning of vacuum-packaged lotus root has not been studied. The effects of vacuum packaging on browning, phenolic content, the enzyme activity of phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD), and PPO, PAL, POD, and ERF genes expression in fresh-cut lotus root were studied. Downregulation of NnPAL1, NnPPOA, and NnPOD2/3 attributable to vacuum packaging coincided with increased related enzyme activities and the degree of browning of fresh-cut lotus root. The expression patterns of NnERF4/5 were consistent with the changes in NnPAL1, NnPPOA, and NnPOD2/3 gene expression. It has been proposed that NnERF4/5 could have be important regulators of fresh-cut lotus root browning, and that the relationships of NnERF4/5 and NnPAL1, NnPPOA, and NnPOD2/3 should to be studied further.

The rice ethylene response factor OsERF83 positively regulates disease resistance to Magnaporthe oryzae

Rice blast caused by Magnaporthe oryzae is one of the most destructive diseases of rice (Oryza sativa) worldwide. Here, we report the identification and functional characterization of a novel ethylene response factor (ERF) gene, OsERF83, which was expressed in rice leaves in response to rice blast fungus infection. OsERF83 expression was also induced by treatments with methyl jasmonate, ethephon, and salicylic acid, indicating that multiple phytohormones could be involved in the regulation of OsERF83 expression under biotic stress. Subcellular localization and transactivation analyses demonstrated that OsERF83 is a nucleus-localized transcriptional activator. A gel-shift assay using recombinant OsERF83 protein indicated that, like other ERFs, it binds to the GCC box. Transgenic rice plants overexpressing OsERF83 exhibited significantly suppressed lesion formation after rice blast infection, indicating that OsERF83 positively regulates disease resistance in rice. Genes encoding several classes of pathogenesis-related (PR) proteins, including PR1, PR2, PR3, PR5, and PR10, were upregulated in the OsERF83ox plants. Taken together, our findings show that OsERF83 is a novel ERF transcription factor that confers blast resistance by regulating the expression of defense-related genes in rice.

Genome-wide identification and expression analysis reveal the potential function of ethylene responsive factor gene family in response to Botrytis cinerea infection and ovule development in grapes (Vitis vinifera L.).

The prevention of Botrytis cinerea infection and the study of grape seedlessness are very important for grape industries. Finding correlated regulatory genes is an important approach towards understanding their molecular mechanisms. Ethylene responsive factor (ERF) gene family play critical roles in defence networks and the growth of plants. To date, no large-scale study of the ERF proteins associated with pathogen defence and ovule development has been performed in grape (Vitis vinifera L.). In the present study, we identified 113 ERF genes (VvERF) and named them based on their chromosome locations. The ERF genes could be divided into 11 groups based on a multiple sequence alignment and a phylogenetic comparison with homologues from Arabidopsis thaliana. Synteny analysis and Ka/Ks ratio calculation suggested that segmental and tandem duplications contributed to the expansion of the ERF gene family. The evolutionary relationships between the VvERF genes were investigated by exon-intron structure characterisation, and an analysis of the cis-acting regulatory elements in their promoters suggested potential regulation after stress or hormone treatments. Expression profiling after infection with the fungus, B. cinerea, indicated that ERF genes function in responses to pathogen attack. In addition, the expression levels of most ERF genes were much higher during ovule development in seedless grapes, suggesting a role in ovule abortion related to seedlessness. Taken together, these results indicate that VvERF proteins are involved in responses to Botrytis cinerea infection and in grape ovule development. This information may help guide strategies to improve grape production.

Expression of Ethylene Response Factor Genes during Fresh-cut Lotus Root Storage and Browning

Ethylene response factor (ERF) genes have been characterized in numerous plants in which they are involved in responses to biotic and abiotic stress, including cold and heat stress. Cool temperatures is one of the most effective storage methods for delaying browning of fresh-cut lotus (Nelumbo nucifera) root. In model plants, ERF genes have been identified as being responsive to cold and heat stress. Whether ERF is associated with lotus root browning in cooler temperatures has not been studied. In this research, low-temperature storage (4 °C) effectively delayed browning of fresh-cut lotus root. Using RNA sequencing, seven Nelumbo nucifera ERF (NnERF) genes were isolated and studied. Transcriptional analysis indicated NnERF genes responded differently to temperature. NnERF3/4/5 were reduced continuously by a low temperature (4 °C) and NnERF5 was the most strongly downregulated. In contrast, transcripts of NnERF1/2/7 were increased at a low temperature (4 °C). The expression of NnERF6 showed no obvious difference between the two different temperatures. It is proposed that NnERF3/4/5 could be important candidates as regulators of fresh-cut lotus root browning. The roles of other members are also discussed.

Overexpression of ethylene response factors VaERF080 and VaERF087 from Vitis amurensis enhances cold tolerance in Arabidopsis

Low temperature is a vital environmental factor that affects plant growth, development and crop yields. Ethylene response factor (ERF) is a plant specific transcription factor with important roles in stress adaptation. However, the regulatory mechanism on how grapevine responds to cold stress is still unclear. In this study, we isolated and characterized two ERF genes from Vitis amurensis designated as VaERF080 and VaERF087. The function of these two genes was investigated in transgenic Arabidopsis. We found that both VaERF080 and VaERF087 were induced by cold stress and ethylene. The overexpression of these genes in Arabidopsis resulted in enhanced cold tolerance. The VaERF080- and VaERF087-overexpressing (OE) Arabidopsis lines showed lower levels of malondialdehyde (MDA) content and higher activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) under cold stress compared to wild-type (WT) Arabidopsis. Nine representative cold-responsive genes, CBF1, CBF2, ICE1, ZAT12, KIN1, SIZ1, RD29A, COR15A, and COR47, were significantly upregulated in OE Arabidopsis. These results revealed that both VaERF080 and VaERF087 may improve the cold tolerance of transgenic Arabidopsis through increasing antioxidant enzyme activities and regulating the expression of cold-related genes.

The distinct ripening processes in the reproductive and non-reproductive parts of the fig syconium are driven by ABA.

The common fig bears a unique closed inflorescence structure, the syconium, composed of small individual drupelets that develop from the ovaries, which are enclosed in a succulent receptacle of vegetative origin. The fig ripening process is traditionally classified as climacteric; however, recent studies have suggested that distinct mechanisms exist in its reproductive and non-reproductive parts. We analysed ABA and ethylene production, and expression of ABA-metabolism, ethylene-biosynthesis, MADS-box, NAC, and ethylene response-factor genes in inflorescences and receptacles of on-tree fruit treated with ABA, ethephon, fluridone, and nordihydroguaiaretic acid (NDGA). Exogenous ABA and ethephon accelerated fruit ripening and softening, whereas fluridone and NDGA had the opposite effect, delaying endogenous ABA and ethylene production compared to controls. Expression of the ABA-biosynthesis genes FcNCED2 and FcABA2, ethylene-biosynthesis genes FcACS4, FcACOL, and FcACO2, FcMADS8, 14, 15, FcNAC1, 2, 5, and FcERF9006 was up-regulated by exogenous ABA and ethephon. NDGA down-regulated FcNCED2 and FcABA2, whereas fluridone down-regulated FcABA2; both down-regulated the ethylene-related genes. These results demonstrate the key role of ABA in regulation of ripening by promoting ethylene production, as in the climacteric model plant tomato, especially in the inflorescence. However, increasing accumulation of endogenous ABA until full ripeness and significantly low expression of ethylene-biosynthesis genes in the receptacle suggests non-climacteric, ABA-dependent ripening in the vegetative-originated succulent receptacle part of the fruit.

Ethylene responsive factor ERF110 mediates ethylene-regulated transcription of a sex determination-related orthologous gene in two Cucumis species.

In plants, unisexual flowers derived from developmental sex determination form separate stamens and pistils that facilitate cross pollination. In cucumber and melon, ethylene plays a key role in sex determination. Six sex determination-related genes have been identified in ethylene biosynthesis in these Cucumis species. The interactions among these genes are thought to involve ethylene signaling; however, the underlying mechanism of regulation remains unknown. In this study, hormone treatment and qPCR assays were used to confirm expression of these sex determination-related genes in cucumber and melon is ethylene sensitive. RNA-Seq analysis subsequently helped identify the ethylene responsive factor (ERF) gene, CsERF110, related to ethylene signaling and sex determination. CsERF110 and its melon ortholog, CmERF110, shared a conserved AP2/ERF domain and showed ethylene-sensitive expression. Yeast one-hybrid and ChIP-PCR assays further indicated that CsERF110 bound to at least two sites in the promoter fragment of CsACS11, while transient transformation analysis showed that CsERF110 and CmERF110 enhance CsACS11 and CmACS11 promoter activity, respectively. Taken together, these findings suggest that CsERF110 and CmERF110 respond to ethylene signaling, mediating ethylene-regulated transcription of CsACS11 and CmACS11 in cucumber and melon, respectively. Furthermore, the mechanism involved in its regulation is thought to be conserved in these two Cucumis species.

Molecular cloning and expression analysis of three ThERFs involved in the response to waterlogging stress of Taxodium 'Zhongshanshan406', and subcellular localization of the gene products.

As a subfamily of the APETALA 2/ethylene response element binding protein (AP2/EREBP) transcription factor superfamily, the ethylene response factor (ERF) is widely involved in the regulation of growth and response to various abiotic stresses in plants, and has been shown to be the main transcription factor regulating transcription of the genes related to hypoxia and waterlogging stress. In this study, three ThERF genes, with significant differences in expression profile in response to flooding stress, were identified from the transcriptomics data acquired from Taxodium hybrid ‘Zhongshanshan 406’ (T. mucronatum Tenore × T. distichum (L.) Rich) under waterlogging stress: ThERF15, ThERF39 and ThRAP2.3 (GenBank ID: KY463467, KY463468 and KY463470, respectively).The full-length cDNA of each of the three ERFs was obtained using the RACE (rapid amplification cDNA ends) method, and all three were intron-free. Multiple protein sequence alignments indicated that ThERF15, ThERF39 and ThRAP2.3 proteins all had only one AP2-ERF domain and belonged to the ERF subfamily. A transient gene expression assay demonstrated that ThERF15, ThERF39 and ThRAP2.3 were all localized to the nucleus. Real-time quantitative PCR (qPCR) revealed that the expression of ThERF15, ThERF39 and ThRAP2.3 exhibited significant differences, compared with the control, in response to two levels of flooding treatment (half-flooding or total-submergence) of ‘Zhongshanshan 406’. Quantification of ethylene concentration revealed that ethylene was more relevant to the level of expression than the period of flooding treatment. Based on the experimental results above, ThERF15, ThERF39 and ThRAP2.3 were identified as being related to the regulation of downstream flooding- responsive gene expression in ‘Zhongshanshan 406’. ThRAP2.3 is most likely to be a key downstream-response ERF gene to respond to the output of the ethylene signal generated by flooding stress.

A Genome-Wide Association Study of Apple Quality and Scab Resistance.

The apple ( × Borkh.) is an economically and culturally important crop grown worldwide. Growers of this long-lived perennial must produce fruit of adequate quality while also combatting abiotic and biotic stress. Traditional apple breeding can take up to 20 yr from initial cross to commercial release, but genomics-assisted breeding can help accelerate this process. To advance genomics-assisted breeding in apple, we performed genome-wide association studies (GWAS) and genomic prediction in a collection of 172 apple accessions by linking over 55,000 single nucleotide polymorphisms (SNPs) with 10 phenotypes collected over 2 yr. Genome-wide association studies revealed several known loci for skin color, harvest date and firmness at harvest. Several significant GWAS associations were detected for resistance to a major fungal pathogen, apple scab ( [Cke.] Wint.), but we demonstrate that these hits likely represent a single ancestral source. Using genomic prediction, we show that most phenotypes are sufficiently predictable using genome-wide SNPs to be candidates for genomic selection. Finally, we detect a signal for firmness retention after storage on chromosome 10 and show that it may not stem from variation in , a gene repeatedly identified in bi-parental mapping studies and widely believed to underlie a major QTL for firmness on chromosome 10. We provide evidence that this major QTL is more likely due to variation in a neighboring ethylene response factor (ERF) gene. The present study showcases the superior mapping resolution of GWAS compared to bi-parental linkage mapping by identifying a novel candidate gene underlying a well-studied, major QTL involved in apple firmness.

Transcriptome analysis unravels an ethylene response factor involved in regulating fruit ripening in pear.

Ethylene response factor (ERF) has been widely studied in regulating fruit ripening in tomato, apple, banana and kiwifruit, but little is known in pear. In this study 1-methylcyclopropene (1-MCP) treatment, an inhibitor of ethylene perception, was conducted at approximately 30 days before harvest to delay fruit ripening in a climacteric white pear cultivar Yali. Transcriptome libraries were constructed and sequenced in pre-ripening, ripening, and 1-MCP treated fruits. Data analysis showed that 73 candidate genes related to fruit ripening were induced by 1-MCP, among which two were positively related, namely 1-aminocyclopropane-1-carboxyla oxidase and an ERF gene (designated as ACO54 and ERF24). Transient transformations in pear fruit revealed that over-expression of ACO54 enhance transcription level of ERF24 and most ripening-related genes. Meanwhile, over-expression of ERF24 raises expression level of ACO54 and partially ripening-related genes. Moreover, dual-luciferase and yeast-one-hybrid assays unravel an interaction between ERF24 and the ACO54 promoter. Therefore, the ERF24 could directly regulate ACO54 expression by binding to its promoter. These results suggested that the first identified ERF24 is involved in regulating fruit ripening in Chinese white pear.

The function of ETHYLENE RESPONSE FACTOR genes in the light-induced anthocyanin production of Arabidopsis thaliana leaves.

Plants grow under threats of environmental changes that could injure cellular viability and damage whole-plant physiology. To defend themselves against such threats, plants induce protective responses, including the production of defense molecules. The red/purple pigment anthocyanin is synthesized upon leaf and fruit development as well as environmental stimuli such as excess light exposure. Therefore, the anthocyanin biosynthesis is considered as a model signaling pathway of the integration of developmental and environmental responses. This integration is tightly regulated by transcription factors, but the integrative mode of these signaling pathways has received little attention. In this study, using an Arabidopsis mutant with mutation in two ETHYLENE RESPONSE FACTOR (ERF) genes, AtERF4 and AtERF8, we investigated the regulatory signaling pathway that leads to the production of anthocyanin in response to light. We detected the accumulation of anthocyanin in detached leaves after incubation on water under light illumination and intact leaves after being transferred into the strong light condition, suggesting that the photoinhibition mediated the production of anthocyanin. Our results demonstrated that the erf mutant decreased the rate and extent of the production of anthocyanin in association with changes of the transcript levels of anthocyanin-biosynthetic genes. As these ERF genes are known regulators of leaf senescence-the final stage of leaf development-we provide an insight into the ERF-mediated integration of two regulatory pathways of the light response and developmental age.

A Critical Review of Submergence Tolerance Breeding Beyond Sub 1 Gene to Mega Varieties in the Context of Climate Change

Flash flood, stagnant flooding and anaerobic germination are various forms of submergence that occurs at different stages of rice growth causing significant damage to crop production for more than 15 millions poor farmers in the rainfed lowland region of South and Southeast. Before the discovery of Sub 1 gene farmers had to rely on low yielding, submergence-intolerant varieties that incurred yield drastic reduction to complete failure of the crop every year. With the discovery of major quantitative trait loci (QTL) submergence 1 (Sub 1) which is responsible for this trait, submergence tolerance breeding has achieved its milestone to overcome the burning issue. Cloning and isolation of SUB1 locus in popular submergence tolerance parent FR13A that led to the identification of ethylene-responsive factor (ERF) gene SUB1A-1 that is responsible for submergence tolerance. The Sub 1 QTL is a single gene that has the LOD score of 36 which explained phenotypic variance of 69% conferring tolerance to complete submergence of two weeks. The submergence -1 (Sub-1) locus representing a cluster of three ethylene responsive factor (ERF) genes: sub1A, sub1B and sub1C. Identification of the SUB1 gene was the entry point for enabled marker assisted selection(MAS) for submergence tolerance. Popular varieties also are known as mega varieties which possessed high yielding and good grain quality was used as the recurrent parent in marker assisted backcrossing (MABC). Beyond the Sub 1 varieties, the present day rice breeders paid attention to tolerance to stagnant flooding and tolerance to anaerobic germination under deep water and flash flood during seedling germination respectively. Quantitative Trait Loci (QTLs) have been identified for anaerobic germination also referred to as AG (AG1 and AG2) and stagnant flooding for deepwater rice (SNORKEL1 and SNORKEL2). Furthermore, the combination of both traits conferring tolerance to stagnant flooding with Sub 1 or Sub 1 with anaerobic germination (AG) is the future direction of rice breeding through gene pyramiding approach to develop the rice varieties tolerant to multiple stresses to enhance yield and quality to combat the future challenge of food and nutritional insecurity.

Transcriptional responses to phosphate starvation in Brachypodium distachyon roots

Brachypodium distachyon is a model plant that has recently emerged in grass research. Although the growth and photochemical efficiency of this species respond strongly to phosphate (Pi) availability, its Pi starvation response mechanism, which controls the Pi homeostasis, remains largely unknown. This study presents the transcriptomic response profiles of Pi-deficient roots at growth stages during which the plants were starved but obvious growth defects were absent. The results identify several phosphate transporters (i.e., PHO1), purple acid phosphatases, and SYG1/PHO81/XPR1 (SPX) domain-containing proteins out of a total of 1740 differentially expressed genes (DEGs). In particular, the transcription factor ethylene response factor (ERF), basic helix-loop-helix (bHLH), and WRKY family genes were the three most abundant DEG groups and the latter was significantly enriched. Comparative transcriptome analysis of Brachypodium versus Arabidopsis and rice revealed the presence of several common components in response to Pi fluctuations. Most significantly, jasmonic acid (JA) signaling-related genes were overrepresented in gene ontology (GO) enrichment tests. The presence of a possible link between low Pi response, inositol polyphosphates, and JA signaling is therefore discussed.

A novel AP2/ERF family transcription factor from Glycine soja, GsERF71, is a DNA binding protein that positively regulates alkaline stress tolerance in Arabidopsis.

Here we first found that GsERF71, an ERF factor from wild soybean could increase plant alkaline stress tolerance by up-regulating H+-ATPase and by modifing the accumulation of Auxin. Alkaline soils are widely distributed all over the world and greatly limit plant growth and development. In our previous transcriptome analyses, we have identified several ERF (ethylene-responsive factor) genes that responded strongly to bicarbonate stress in the roots of wild soybean G07256 (Glycine soja). In this study, we cloned and functionally characterized one of the genes, GsERF71. When expressed in epidermal cells of onion, GsERF71 localized to the nucleus. It can activate the reporters in yeast cells, and the C-terminus of 170 amino acids is essential for its transactivation activity. Yeast one-hybrid and EMSA assays indicated that GsERF71 specifically binds to the cis-acting elements of the GCC-box, suggesting that GsERF71 may participate in the regulation of transcription of the relevant biotic and abiotic stress-related genes. Furthermore, transgenic Arabidopsis plants overexpressing GsERF71 showed significantly higher tolerance to bicarbonate stress generated by NaHCO3 or KHCO3 than the wild type (WT) plants, i.e., the transgenic plants had greener leaves, longer roots, higher total chlorophyll contents and lower MDA contents. qRT-PCR and rhizosphere acidification assays indicated that the expression level and activity of H+-ATPase (AHA2) were enhanced in the transgenic plants under alkaline stress. Further analysis indicated that the expression of auxin biosynthetic genes and IAA contents were altered to a lower extent in the roots of transgenic plants than WT plants under alkaline stress in a short-term. Together, our data suggest that GsERF71 enhances the tolerance to alkaline stress by up-regulating the expression levels of H+-ATPase and by modifying auxin accumulation in transgenic plants.

A model for evolution and regulation of nicotine biosynthesis regulon in tobacco

ABSTRACTIn tobacco, the defense alkaloid nicotine is produced in roots and accumulates mainly in leaves. Signaling mediated by jasmonates (JAs) induces the formation of nicotine via a series of structural genes that constitute a regulon and are coordinated by JA-responsive transcription factors of the ethylene response factor (ERF) family. Early steps in the pyrrolidine and pyridine biosynthesis pathways likely arose through duplication of the polyamine and nicotinamide adenine dinucleotide (NAD) biosynthetic pathways, respectively, followed by recruitment of duplicated primary metabolic genes into the nicotine biosynthesis regulon. Transcriptional regulation of nicotine biosynthesis by ERF and cooperatively-acting MYC2 transcription factors is implied by the frequency of cognate cis-regulatory elements for these factors in the promoter regions of the downstream structural genes. Indeed, a mutant tobacco with low nicotine content was found to have a large chromosomal deletion in a cluster of closely related ERF genes at the nicotine-controlling NICOTINE2 (NIC2) locus.