Ethylene Response Factor Research Articles

Genome-Wide Identification of the ERF Transcription Factor Family for Structure Analysis, Expression Pattern, and Response to Drought Stress in Populus alba × Populus glandulosa.

The Ethylene Responsive Factor (ERF) transcription factor family is important for regulating plant growth and stress responses. Although the expression patterns of ERF family members have been reported in many plant species, their role in Populus alba × Populus glandulosa, an important model plant for forest research, remains unclear. In this study, we identified 209 PagERF transcription factors by analyzing the P. alba × P. glandulosa genome. We analyzed their amino acid sequences, molecular weight, theoretical pI (Isoelectric point), instability index, aliphatic index, grand average of hydropathicity, and subcellular localization. Most PagERFs were predicted to localize in the nucleus, with only a few PagERFs localized in the cytoplasm and nucleus. Phylogenetic analysis divided the PagERF proteins into ten groups, Class I to X, with those belonging to the same group containing similar motifs. Cis-acting elements associated with plant hormones, abiotic stress responses, and MYB binding sites were analyzed in the promoters of PagERF genes. We used transcriptome data to analyze the expression patterns of PagERF genes in different tissues of P. alba × P. glandulosa, including axillary buds, young leaves, functional leaves, cambium, xylem, and roots, and the results indicated that PagERF genes are expressed in all tissues of P. alba × P. glandulosa, especially in roots. Quantitative verification results were consistent with transcriptome data. When P. alba × P. glandulosa seedlings were treated with 6% polyethylene glycol 6000 (PEG6000), the results of RT-qRCR showed that nine PagERF genes responded to drought stress in various tissues. This study provides a new perspective on the roles of PagERF family members in regulating plant growth and development, and responses to stress in P. alba × P. glandulosa. Our study provides a theoretical basis for ERF family research in the future.

Metal-responsive elements confer cadmium response in Arabidopsis.

Molecular, biochemical, and genetic experiments demonstrate that metal-responsive elements (MREs), initially identified in animals, confer the cadmium transcriptional response in Arabidopsis, thus providing deep functional insights of MREs in plants. Cadmium (Cd) is highly toxic to all organisms including plants. Cd-responsive gene transcription is a fundamental aspect of the Cd response, in which Cd stress regulatory cis-acting elements are essential. However, little is known regarding such elements in plants. Metal-responsive elements (MREs, 5'-TGCRCNC-3', R: A or G, N: any base) are essential for transcriptional induction of Cd in animals. MREs are also contained in the promoters of some Cd-regulated plant genes, but whether MREs confer Cd responses in plants is poorly defined. Herein, we used a previously identified MRE of the tobacco feedback-insensitive anthranilate synthase α-2 chain gene as a representative MRE (named as MREa, 5'-TGCACAC-3') to explore the roles of MREs in the transcriptional response to Cd stress in Arabidopsis thaliana. First, we showed that MREa conferred Cd stress responsiveness on a minimal promoter in both concentration- and time-dependent manners, whereas the mutated MREa did not. Second, MREa specifically bound nuclear extracts, displaying a biochemical characteristic of cis-acting elements. We screened and identified four MREa-binding transcription factors, including ethylene response factor 13 (AtERF13). At last, MREa could mediate AtERF13 to activate the β-glucuronidase (GUS) reporter expression. Overall, these molecular, biochemical, and genetic data suggest that MREa is instrumental in the Cd response in Arabidopsis, thus providing deep functional insights of MREs in plants.

Single-cell transcriptomic analysis reveals the developmental trajectory and transcriptional regulatory networks of pigment glands in Gossypium bickii

Comprehensive utilization of cottonseeds is limited by the presence of pigment glands and its inclusion gossypol. The ideal cotton has glandless seeds but a glanded plant, a trait found in only a few Australian wild cotton species, including Gossypium bickii. Introgression of this trait into cultivated species has proved to be difficult. Understanding the biological processes toward pigment gland morphogenesis and the associated underlying molecular mechanisms will facilitate breeding of cultivated cotton varieties with the trait of glandless seeds and glanded plant. In this study, single-cell RNA sequencing (scRNA-seq) was performed on 12 222 protoplasts isolated from cotyledons of germinating G. bickii seeds 48 h after imbibition. Clustered into 14 distinct clusters unsupervisedly, these cells could be grouped into eight cell populations with the assistance of known cell marker genes. The pigment gland cells were well separated from others and could be separated into pigment gland parenchyma cells, secretory cells, and apoptotic cells. By integrating the pigment gland cell developmental trajectory, transcription factor regulatory networks, and core transcription factor functional validation, we established a model for pigment gland formation. In this model, light and gibberellin were verified to promote the formation of pigment glands. In addition, three novel genes, GbiERF114 (ETHYLENE RESPONSE FACTOR 114), GbiZAT11 (ZINC FINGER OF ARABIDOPSIS THALIANA 11), and GbiNTL9 (NAC TRANSCRIPTION FACTOR-LIKE 9), were found to affect pigment gland formation. Collectively, these findings provide new insights into pigment gland morphogenesis and lay the cornerstone for future cotton scRNA-seq investigations.

PAT1-type GRAS-domain proteins control regeneration by activating DOF3.4 to drive cell proliferation in Arabidopsis roots.

Plant roots possess remarkable regenerative potential owing to their ability to replenish damaged or lost stem cells. ETHYLENE RESPONSE FACTOR 115 (ERF115), one of the key molecular elements linked to this potential, plays a predominant role in the activation of regenerative cell divisions. However, the downstream operating molecular machinery driving wound-activated cell division is largely unknown. Here, we biochemically and genetically identified the GRAS-domain transcription factor SCARECROW-LIKE 5 (SCL5) as an interaction partner of ERF115 in Arabidopsis thaliana. Although nonessential under control growth conditions, SCL5 acts redundantly with the related PHYTOCHROME A SIGNAL TRANSDUCTION 1 (PAT1) and SCL21 transcription factors to activate the expression of the DNA-BINDING ONE FINGER 3.4 (DOF3.4) transcription factor gene. DOF3.4 expression is wound-inducible in an ERF115-dependent manner and, in turn, activates D3-type cyclin expression. Accordingly, ectopic DOF3.4 expression drives periclinal cell division, while its downstream D3-type cyclins are essential for the regeneration of a damaged root. Our data highlight the importance and redundant roles of the SCL5, SCL21, and PAT1 transcription factors in wound-activated regeneration processes and pinpoint DOF3.4 as a key downstream element driving regenerative cell division.

ETHYLENE RESPONSE FACTORS 4.1/4.2 with an EAR motif repress anthocyanin biosynthesis in red-skinned pears.

Red-skinned pears (Pyrus L.) are preferred to consumers for their attractive color and abundant anthocyanins. Pyrus ETHYLENE RESPONSE FACTOR 3 (PyERF3) positively regulates anthocyanin biosynthesis through interacting with Pyrus myeloblastosis family 114 (PyMYB114) and Pyrus basic helix-loop-helix 3 (PybHLH3) in red-skinned pears. However, the role of APETALA2/ethylene response factors (AP2/ERFs), which negatively regulate anthocyanin biosynthesis, remains unclear in red-skinned pears. Here, we validated that 2 AP2/ERFs, PyERF4.1 and PyERF4.2, screened from the transcriptome data of 'Starkrimson' pear (Pyrus communis L.) and its green mutant, inhibit anthocyanin biosynthesis in transgenic pear calli, as well as in overexpression and gene-edited tomato (Solanum lycopersicum) fruits. Meanwhile, the co-transformation of PyERF4.1/PyERF4.2 with PyERF3-PyMYB114-PybHLH3 inhibited anthocyanin biosynthesis in pear fruits and strawberry (Fragaria vesca) receptacles. Further assays showed that PyMYB114 activated the transcription of PyERF4.1/PyERF4.2; PyERF4.1/PyERF4.2 then interacted with PyERF3 to affect the stability of the PyERF3-PyMYB114-PybHLH3 complex, thereby inhibiting the transcription of the anthocyanin biosynthesis gene Pyrus anthocyanidin synthase (PyANS). Furthermore, deletion of the ERF-associated-amphiphilic repression (EAR) motif eliminated the inhibitory effect of PyERF4.1/PyERF4.2 on anthocyanin biosynthesis, and a mutation of the PyERF4.2-EAR motif (LxLxM to LxLxL) strengthened the inhibitory effect, demonstrating that the EAR motif is indispensable for the inhibitory effect of PyERF4.1/PyERF4.2 on anthocyanin biosynthesis in pears. Our study has shed light on a feedback regulatory loop mechanism that balances the excessive accumulation of anthocyanins in red-skinned pears, providing insights into the regulatory mechanism of anthocyanin biosynthesis and the regulatory network of coloration in red-skinned pears.

Melatonin Delays Postharvest Senescence through Suppressing the Inhibition of BrERF2/BrERF109 on Flavonoid Biosynthesis in Flowering Chinese Cabbage.

Flowering Chinese cabbage is prone to withering, yellowing and deterioration after harvest. Melatonin plays a remarkable role in delaying leaf senescence and increasing flavonoid biosynthesis. However, the underlying molecular mechanisms of melatonin procrastinating postharvest senescence by regulating flavonoid biosynthesis remain largely unknown. In this study, melatonin could promote flavonoid accumulation and delay the postharvest senescence of flowering Chinese cabbage. Surprisingly, we observed that BrFLS1 and BrFLS3.2 were core contributors in flavonoid biosynthesis, and BrERF2 and BrERF109 were crucial ethylene response factors (ERFs) through the virus-induced gene silencing (VIGS) technique, which is involved in regulating the postharvest senescence under melatonin treatment. Furthermore, yeast one-hybrid (Y1H), dual luciferase (LUC), and β-glucuronidase (GUS) tissue staining experiments demonstrated that BrERF2/BrERF109 negatively regulated the transcripts of BrFLS1 and BrFLS3.2 by directly binding to their promoters, respectively. Silencing BrERF2/BrERF109 significantly upregulated the transcripts of BrFLS1 and BrFLS3.2, promoting flavonoid accumulation, and postponing the leaf senescence. Our results provided a new insight into the molecular regulatory network of melatonin delaying leaf senescence and initially ascertained that melatonin promoted flavonoid accumulation by suppressing the inhibition of BrERF2/BrERF109 on the transcripts of BrFLS1 and BrFLS3.2, which led to delaying the leaf senescence of postharvest flowering Chinese cabbage.

RsERF40 contributes to cold stress tolerance and cell expansion of taproot in radish (Raphanus sativus L.).

The growth and development of taproots are inhibited by cold stress in radish (Raphanus sativus L.). Ethylene-responsive element binding factors (ERF) are key participators in the cold stress response and growth regulation of plants. However, the function of ERF genes in cold tolerance and root development in radish remains elusive. Here, we showed that the secondary growth of radish taproots was inhibited by cold stress. Comparative transcriptome analysis demonstrated that the RsERF40 gene is an important regulator of the cold stress response and root growth regulation. The cold tolerance of transgenic Arabidopsis plants overexpressing the RsERF40 gene was significantly improved. Overexpressing RsERF40 in the cold-sensitive radish genotype and silencing RsERF40 in the cold-tolerant radish genotype indicated that RsERF40 was beneficial for alleviating oxidative damage under cold stress in radish. Transgenic Arabidopsis seedlings showed an increase in the elongation and radial growth of dark-grown roots. RT-qPCR analysis showed that the expression of the cold-related genes (CORs) RsCOR78 and RsCOR413PM1 and the cell wall strengthening-related genes RsCESA6 and RsEXPB3 was upregulated in transgenic Arabidopsis seedlings. Yeast one-hybrid (Y1H) and dual-luciferase reporter assays (DLA) revealed that RsERF40 directly regulates RsCOR78, RsCOR413PM1, RsCESA6 and RsEXPB3 expression, illustrating that RsERF40 enhances cold tolerance and taproot growth by modulating osmotic adjustment and cell wall mechanical strength in radish. In this study, the RsERF40-regulon was firstly found to be a new cold response pathway independent of the CBF-COR pathway conferring cold stress tolerance with increasing radish taproot growth. These results provided novel insight into the molecular mechanism underlying cold stress response and would facilitate the genetic improvement of cold tolerance in radish and other root vegetable crops.

MdERF114 enhances the resistance of apple roots to Fusarium solani by regulating the transcription of MdPRX63.

As the main fungal etiologic agent of apple (Malus domestica) replant disease (ARD), Fusarium solani seriously damages apple roots. Ethylene response factors (ERFs) play an important role in plant resistance to biotic stress. Here, we show that MdERF114 is expressed during F. solani infections and positively regulates the resistance of apple roots to F. solani. Yeast one-hybrid, dual-luciferase, electrophoretic mobility shift assays and determinations of lignin content indicated that MdERF114 directly binds the GCC-box of the MdPEROXIDASE63 (MdPRX63) promoter and activates its expression, resulting in lignin deposition in apple roots and increased resistance to F. solani. We identified a WRKY family transcription factor, MdWRKY75, that binds to the W-box of the MdERF114 promoter. Overexpression of MdWRKY75 enhanced resistance of apple roots to F. solani. MdMYB8 interacted with MdERF114 to enhance resistance to F. solani by promoting the binding of MdERF114 to the MdPRX63 promoter. In summary, our findings reveal that the MdWRKY75-MdERF114-MdMYB8-MdPRX63 module is required for apple resistance to F. solani and the application of this mechanism by Agrobacterium rhizogenes-mediated root transformation provides a promising strategy to prevent ARD.

Evolution of wound-activated regeneration pathways in the plant kingdom

Regeneration serves as a self-protective mechanism that allows a tissue or organ to recover its entire form and function after suffering damage. However, the regenerative capacity varies greatly within the plant kingdom. Primitive plants frequently display an amazing regenerative ability as they have developed a complex system and strategy for long-term survival under extreme stress conditions. The regenerative ability of dicot species is highly variable, but that of monocots often exhibits extreme recalcitrance to tissue replenishment. Recent studies have revealed key factors and signals that affect cell fate during plant regeneration, some of which are conserved among the plant lineage. Among these, several members of the ETHYLENE RESPONSE FACTOR (ERF) transcription factors have been implicated in wound signaling, playing crucial roles in the regenerative mechanisms after different types of wounding. An understanding of plant regeneration may ultimately lead to an increased regenerative potential of recalcitrant species, producing more high-yielding, multi-resistant and environmentally friendly crops and ensuring the long-term development of global agriculture.

Comparative and expression analyses of AP2/ERF genes reveal copy number expansion and potential functions of ERF genes in Solanaceae

BackgroundThe AP2/ERF gene family is a superfamily of transcription factors that are important in the response of plants to abiotic stress and development. However, comprehensive research of the AP2/ERF genes in the Solanaceae family is lacking.ResultsHere, we updated the annotation of AP2/ERF genes in the genomes of eight Solanaceae species, as well as Arabidopsis thaliana and Oryza sativa. We identified 2,195 AP2/ERF genes, of which 368 (17%) were newly identified. Based on phylogenetic analyses, we observed expansion of the copy number of these genes, especially those belonging to specific Ethylene-Responsive Factor (ERF) subgroups of the Solanaceae. From the results of chromosomal location and synteny analyses, we identified that the AP2/ERF genes of the pepper (Capsicum annuum), the tomato (Solanum lycopersicum), and the potato (Solanum tuberosum) belonging to ERF subgroups form a tandem array and most of them are species-specific without orthologs in other species, which has led to differentiation of AP2/ERF gene repertory among Solanaceae. We suggest that these genes mainly emerged through recent gene duplication after the divergence of these species. Transcriptome analyses showed that the genes have a putative function in the response of the pepper and tomato to abiotic stress, especially those in ERF subgroups.ConclusionsOur findings will provide comprehensive information on AP2/ERF genes and insights into the structural, evolutionary, and functional understanding of the role of these genes in the Solanaceae.

Wide-Range Portrayal of AP2/ERF Transcription Factor Family in Maize (Zea mays L.) Development and Stress Responses.

The APETALA2/Ethylene-Responsive Transcriptional Factors containing conservative AP2/ERF domains constituted a plant-specific transcription factor (TF) superfamily, called AP2/ERF. The configuration of the AP2/ERF superfamily in maize has remained unresolved. In this study, we identified the 229 AP2/ERF genes in the latest (B73 RefGen_v5) maize reference genome. Phylogenetic classification of the ZmAP2/ERF family members categorized it into five clades, including 27 AP2 (APETALA2), 5 RAV (Related to ABI3/VP), 89 DREB (dehydration responsive element binding), 105 ERF (ethylene responsive factors), and a soloist. The duplication events of the paralogous genes occurred from 1.724-25.855 MYA, a key route to maize evolution. Structural analysis reveals that they have more introns and few exons. The results showed that 32 ZmAP2/ERFs regulate biotic stresses, and 24 ZmAP2/ERFs are involved in responses towards abiotic stresses. Additionally, the expression analysis showed that DREB family members are involved in plant sex determination. The real-time quantitative expression profiling of ZmAP2/ERFs in the leaves of the maize inbred line B73 under ABA, JA, salt, drought, heat, and wounding stress revealed their specific expression patterns. Conclusively, this study unveiled the evolutionary pathway of ZmAP2/ERFs and its essential role in stress and developmental processes. The generated information will be useful for stress resilience maize breeding programs.

Salicylic acid delays pear fruit senescence by playing an antagonistic role toward ethylene, auxin, and glucose in regulating the expression of PpEIN3a.

Salicylic acid (SA) and ethylene (ET) are crucial fruit senescence hormones. SA inhibited ET biosynthesis. However, the mechanism of SA delaying fruit senescence is less known. ETHYLENE INSENSITIVE 3 (EIN3), a key positive switch in ET perception, functions as a transcriptional activator and binds to the primary ET response element that is present in the promoter of the ETHYLENE RESPONSE FACTOR1 gene. In this study, a gene encoding putative EIN3 protein was cloned from sand pear and designated as PpEIN3a. The deduced PpEIN3a contains a conserved EIN3 domain. The evolutionary analysis results indicated that PpEIN3a belonged to the EIN3 superfamily. Real-time quantitative PCR analysis revealed that the accumulation of PpEIN3a transcripts were detected in all tissues of this pear. Moreover, PpEIN3a expression was regulated during fruit development. Interestingly, the expression of PpEIN3a was downregulated by SA but upregulated by ET, auxin, and glucose. Additionally, the contents of free and conjugated SA were higher than those of the control after SA treatment. While the content of ET and auxin (indole-3-acetic acid, IAA) dramatically decreased after SA treatment compared with control during fruit senescence. The content of glucose increased when fruit were treated by SA for 12h and then there were no differences between SA treatment and control fruit during the shelf life. SA also delayed the decrease in sand pear (Pyrus pyrifolia Nakai. 'Whangkeumbae') fruit firmness. The soluble solid content remained relatively stable between the SA treated and control fruits. This study showed that SA plays an antagonistic role toward ET, auxin, and glucose in regulating the expression of PpEIN3a to delay fruit senescence.

Development of a MAGIC population and high-resolution quantitative trait mapping for nicotine content in tobacco.

Multiparent Advanced Generation Inter-Cross (MAGIC) population is an ideal genetic and breeding material for quantitative trait locus (QTL) mapping and molecular breeding. In this study, a MAGIC population derived from eight tobacco parents was developed. Eight parents and 560 homozygous lines were genotyped by a 430K single-nucleotide polymorphism (SNP) chip assay and phenotyped for nicotine content under different conditions. Four QTLs associated with nicotine content were detected by genome-wide association mapping (GWAS), and one major QTL, named qNIC7-1, was mapped repeatedly under different conditions. Furthermore, by combining forward mapping, bioinformatics analysis and gene editing, we identified an ethylene response factor (ERF) transcription factor as a candidate gene underlying the major QTL qNIC7-1 for nicotine content in tobacco. A presence/absence variation (PAV) at qNIC7-1 confers changes in nicotine content. Overall, the large size of this MAGIC population, diverse genetic composition, balanced parental contributions and high levels of recombination all contribute to its value as a genetic and breeding resource. The application of the tobacco MAGIC population for QTL mapping and detecting rare allelic variation was demonstrated using nicotine content as a proof of principle.

Target of rapamycin signaling couples energy to oxygen sensing to modulate hypoxic gene expression in Arabidopsis

Plants respond to oxygen deprivation by activating the expression of a set of hypoxia-responsive genes (HRGs). The master regulator of this process is a small group of transcription factors belonging to group VII of the ethylene response factors (ERF-VIIs). ERF-VIIs are highly unstable under aerobic conditions due to the continuous oxidation of their characteristic Cys residue at the N terminus by plant cysteine oxidases (PCOs). Under hypoxia, PCOs are inactive and the ERF-VIIs activate transcription of the HRGs required for surviving hypoxia. However, if the plant exposed to hypoxia has limited sugar reserves, the activity of ERF-VIIs is severely dampened. This suggests that oxygen sensing by PCO/ERF-VII is fine-tuned by another sensing pathway, related to sugar or energy availability. Here, we show that oxygen sensing by PCO/ERF-VII is controlled by the energy sensor target of rapamycin (TOR). Inhibition of TOR by genetic or pharmacological approaches leads to a much lower induction of HRGs. We show that two serine residues at the C terminus of RAP2.12, a major ERF-VII, are phosphorylated by TOR and are needed for TOR-dependent activation of transcriptional activity of RAP2.12. Our results demonstrate that oxygen and energy sensing converge in plants to ensure an appropriate transcription of genes, which is essential for surviving hypoxia. When carbohydrate metabolism is inefficient in producing ATP because of hypoxia, the lower ATP content reduces TOR activity, thus attenuating the efficiency of induction of HRGs by the ERF-VIIs. This homeostatic control of the hypoxia-response is required for the plant to survive submergence.

Phy meets ERFs to regulate seed germination.

The complex process of seed germination is impacted heavily by environmental cues, such as light, mediated via photosensory systems and phytochromes. This pathway was discovered a long time ago, but the underlying molecular mechanisms are not fully understood. Li et al. recently showed how ETHYLENE RESPONSE FACTORs (ERFs) modulate phytochrome-mediated regulation of germination.

An AP2/ERF transcription factor VvERF63 positively regulates cold tolerance in Arabidopsis and grape leaves

Cold stress adversely impacts grape growth, development, and yield. Thus, enhancing the cold tolerance of grape is a priority for grape breeding. Several APETALA2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF) transcription factors (TFs) play critical roles in plant responses to various abiotic stresses. However, only a few ERF TFs in grape have been identified under various stress. Here, we cloned a novel ERF gene, VvERF63 from ‘Cabernet Sauvignon’ ( Vitis vinifera L . ), which is strongly induced by cold treatment and exogenous abscisic acid (ABA) treatment, and has transcriptional activation activity in yeast. Overexpression of VvERF63 in Arabidopsis improved cold resistance at the seedling and mature stages. Moreover, VvERF63 -overexpressing and silencing grape leaves displayed improved and decreased cold tolerance, respectively. These results indicated that VvERF63 plays a positive role in cold tolerance by enhancing the photosynthetic capacity, and ameliorating cellular damage, which was evidenced by improved maximum photosynthetic efficiency of photosystem II (Fv/Fm), chlorophyll content, lower electrolyte leakage and malondialdehyde, as well as by increased antioxidant enzymes activities in the transgenic Arabidopsis . Additionally, the expression levels of stress- and antioxidant- related genes were upregulated in VvERF63 -overexpressing plants. Our results suggested that VvERF63 positively participated in the cold resistance response and has excellent potential as a candidate gene for improving the cold tolerance of plant. • VvERF63 was an ethylene response factor, the expression of which was induced by cold and ABA treatment. • VvERF63 could increase photosynthetic capacity and enhance membrane stabilization in VvERF63 -overexpressing grape leaves and Arabidopsis under cold stress. • VvERF63 plays a role in cold tolerance by increasing activities of antioxidant enzymes and expression levels of stress-responsive genes. • VvERF63 possibly mediates CBF-COR signal pathway to improve plant cold tolerance in transgenic Arabidopsis and transient transgenic grape leaves.

Ethylene accelerates grape ripening <i>via</i> increasing <i>VvERF75</i>-induced ethylene synthesis and chlorophyll degradation

Ethylene plays an important role in grape ripening, acting through ethylene response factors (ERFs) that are downstream of ethylene signaling pathways, yet little else is known about these molecular mechanisms. In our study, we demonstrate that ethylene treatment promotes grape ripening and that the transcription factor <italic>VvERF75</italic> shows increased expression during grape ripening. <italic>VvERF75</italic> was found to contain a conserved AP2/ERF domain, to be a member of the ERF IXa subfamily, an to localize to the nucleus and to have transactivation activity in yeast. Our in vitro assays showed that <italic>VvERF75</italic> can positively regulate expression of <italic>pheophorbide</italic> a<italic> oxygenase</italic> (<italic>VvPAO1</italic>) and <italic>1-aminocyclopropane-1-carboxylic acid synthase</italic> (<italic>VvACS5</italic>) by binding to DRE motifs in their promoters. Overexpression of <italic>VvERF75</italic> in tomato increased ethylene production and resulted in dwarfed plants, early flowering and fruit ripening, increased <italic>SlPAO</italic> and <italic>SlACS</italic> transcript levels, and decreased chlorophyll content. In general, our study revealed that <italic>VvERF75</italic> may regulate fruit ripening by promoting ethylene biosynthesis and chlorophyll degradation, a discovery that lays a foundation for deciphering the molecular mechanisms of grape ripening.

Molecular mechanism of internode elongation in rice.

Rice plants that form ventilated tissues, such as aerenchyma in the leaves, stems, and roots, allow for growth in waterlogged conditions (paddy fields), but they cannot breathe and drown in flooded environments where the whole plant body is submerged. However, deepwater rice plants grown in flood-prone areas of Southeast Asia survive in prolonged flooded environments by taking in air through an elongated stem (internode) and leaves that emerge above the water surface, even if the water level is several meters high and flooding continues for several months. Although it has been known that plant hormones, such as ethylene and gibberellins, promote internode elongation in deepwater rice plants, the genes that control rapid internode elongation during submergence have not been identified. We recently identified several genes responsible for the quantitative trait loci involved in internode elongation in deepwater rice. Identification of the the genes revealed a molecular gene network from ethylene to gibberellins in which internode elongation is promoted by novel ethylene-responsive factors and enhances gibberellin responsiveness at the internode. In addition, elucidation of the molecular mechanism of internode elongation in deepwater rice will help our understanding of the internode elongation mechanism in normal paddy rice and contribute to improving crops through the regulation of internode elongation.

Os fatores de ligação do elemento responsivo ao etileno contribuem para a tolerância ao encharcamento, regulando os parâmetros fotossintéticos e fisiológicos na petúnia

ABSTRACT: Ethylene-responsive element binding factors (ERFs) are widely involved in the regulation of plant responses to different abiotic stresses. In petunia (Petunia × hybrida), PhERF2 belonging to the subfamily Ⅶ of ERF transcription factors participates in the response to waterlogging stress. In this study, we investigated waterlogging tolerance variation of WT and transgenic petunia plants with RNAi silencing and overexpression of PhERF2 through photosynthetic and physiological performance. Chlorophyll content and root vigor declined continuously in both WT and PhERF2 transgenic lines under waterlogging stress, but the extent of the fall in PhERF2-overexpressing lines was less than that in WT and PhERF2-RNAi lines. At the end of waterlogging treatment, soluble protein levels in PhERF2-overexpressing lines were significantly higher than those in WT and PhERF2-RNAi lines, while the latter showed a higher malondialdehyde content overall. Different degrees of reductions in Pn, Gs, and Tr levels occurred in both WT and PhERF2 transgenic lines upon exposure to waterlogging. The Ci levels of PhERF2-overexpressing lines decreased after 3 hours of waterlogging treatment, and the Ci levels of WT and PhERF2-RNAi lines gradually increased from 6 to 72 hours of waterlogging treatment. These data suggested that non-stomatal factors were the primary limiting factors for Pn in WT and PhERF2-RNAi lines under severe stress, while the stomatal opening was the main factor limiting Pn in PhERF2-overexpressing lines. Our results demonstrated that the contribution of PhERF2 to the waterlogging tolerance of petunia appears to depend on the regulation of physiological and photosynthetic responses. PhERF2 represents a hopeful candidate gene for enhancing waterlogging tolerance of ornamental plants.

Growth-regulating factor 15-mediated gene regulatory network enhances salt tolerance in poplar.

Soil salinity is an important determinant of crop productivity and triggers salt stress response pathways in plants. The salt stress response is controlled by transcriptional regulatory networks that maintain regulatory homeostasis through combinations of transcription factor (TF)-DNA and TF-TF interactions. We investigated the transcriptome of poplar 84 K (Populus alba × Populus glandulosa) under salt stress using samples collected at 4- or 6-h intervals within 2 days of salt stress treatment. We detected 24,973 differentially expressed genes, including 2,231 TFs that might be responsive to salt stress. To explore these interactions and targets of TFs in perennial woody plants, we combined gene regulatory networks, DNA affinity purification sequencing, yeast two-hybrid-sequencing, and multi-gene association approaches. Growth-regulating factor 15 (PagGRF15) and its target, high-affinity K+ transporter 6 (PagHAK6), were identified as an important regulatory module in the salt stress response. Overexpression of PagGRF15 and PagHAK6 in transgenic lines improved salt tolerance by enhancing Na+ transport and modulating H2O2 accumulation in poplar. Yeast two-hybrid assays identified more than 420 PagGRF15-interacting proteins, including ETHYLENE RESPONSE FACTOR TFs and a zinc finger protein (C2H2) that are produced in response to a variety of phytohormones and environmental signals and are likely involved in abiotic stress. Therefore, our findings demonstrate that PagGRF15 is a multifunctional TF involved in growth, development, and salt stress tolerance, highlighting the capability of a multifaceted approach in identifying regulatory nodes in plants.