ZINC-FINGER interactions mediate transcriptional regulation of hypocotyl growth in Arabidopsis

Zinc Finger-Homeodomain Transcriptional Factors (ZHDs) in Cucumber (Cucumis sativus L.): Identification, Evolution, Expression Profiles, and Function under Abiotic Stresses

Cucumber (Cucumis sativus L.) is a globally prevalent and extensively cultivated vegetable whose yield is significantly influenced by various abiotic stresses, including drought, heat, and salinity. Transcription factors, such as zinc finger-homeodomain proteins (ZHDs), a plant-specific subgroup of Homeobox, play a crucial regulatory role in stress resistance. In this study, we identified 13 CsZHDs distributed across all six cucumber chromosomes except chromosome 7. Phylogenetic analysis classified these genes into five clades (ZHDI-IV and MIF) with different gene structures but similar conserved motifs. Collinearity analysis revealed that members of clades ZHD III, IV, and MIF experienced amplification through segmental duplication events. Additionally, a closer evolutionary relationship was observed between the ZHDs in Cucumis sativus (C. sativus) and Arabidopsis thaliana (A. thaliana) compared to Oryza sativa (O. sativa). Quantitative real-time PCR (qRT-PCR) analysis demonstrated the general expression of CsZHD genes across all tissues, with notable expression in leaf and flower buds. Moreover, most of the CsZHDs, particularly CsZHD9-11, exhibited varying responses to drought, heat, and salt stresses. Virus-induced gene silencing (VIGS) experiments highlighted the potential functions of CsZHD9 and CsZHD10, suggesting their positive regulation of stomatal movement and responsiveness to drought stress. In summary, these findings provide a valuable resource for future analysis of potential mechanisms underlying CsZHD genes in response to stresses.

Expression of the Arabidopsis redox-related LEA protein, SAG21 is regulated by ERF, NAC and WRKY transcription factors

SAG21/LEA5 is an unusual late embryogenesis abundant protein in Arabidopsis thaliana, that is primarily mitochondrially located and may be important in regulating translation in both chloroplasts and mitochondria. SAG21 expression is regulated by a plethora of abiotic and biotic stresses and plant growth regulators indicating a complex regulatory network. To identify key transcription factors regulating SAG21 expression, yeast-1-hybrid screens were used to identify transcription factors that bind the 1685 bp upstream of the SAG21 translational start site. Thirty-three transcription factors from nine different families bound to the SAG21 promoter, including members of the ERF, WRKY and NAC families. Key binding sites for both NAC and WRKY transcription factors were tested through site directed mutagenesis indicating the presence of cryptic binding sites for both these transcription factor families. Co-expression in protoplasts confirmed the activation of SAG21 by WRKY63/ABO3, and SAG21 upregulation elicited by oligogalacturonide elicitors was partially dependent on WRKY63, indicating its role in SAG21 pathogen responses. SAG21 upregulation by ethylene was abolished in the erf1 mutant, while wound-induced SAG21 expression was abolished in anac71 mutants, indicating SAG21 expression can be regulated by several distinct transcription factors depending on the stress condition.

Histone Deacetylase Complex 1 and histone 1 epigenetically moderate stress responsiveness of Arabidopsis thaliana seedlings

Early responses of plants to environmental stress factors prevent damage but can delay growth and development in fluctuating conditions. Optimising these trade-offs requires tunability of plant responsiveness to environmental signals. We have previously reported that Histone Deacetylase Complex 1 (HDC1), which interacts with multiple proteins in histone deacetylation complexes, regulates the stress responsiveness of Arabidopsis seedlings, but the underlying mechanism remained elusive. Here, we show that HDC1 attenuates transcriptome re-programming in salt-treated seedlings, and we identify two genes (LEA and MAF5) that inhibit seedling establishment under salt stress downstream of HDC1. HDC1 attenuates their transcriptional induction by salt via a dual mechanism involving H3K9/14 deacetylation and H3K27 trimethylation. The latter, but not the former, was also abolished in a triple knockout mutant of the linker histone H1, which partially mimics the hypersensitivity of the hdc1-1 mutant to salt stress. Although stress-induced H3K27me3 accumulation required both H1 and HDC1, it was not fully recovered by complementing hdc1-1 with a truncated, H1-binding competent HDC1 suggesting other players or independent inputs. The combined findings reveal a dual brake function of HDC1 via regulating both active and repressive epigenetic marks on stress-inducible genes. This natural 'anti-panic' device offers a molecular leaver to tune stress responsiveness in plants.

Distinct early transcriptional regulations by turgor and osmotic potential in the roots of Arabidopsis

In a context of climate change, deciphering signaling pathways driving plant adaptation to drought, changes in water availability, and salt is key. A crossing point of these plant stresses is their impact on plant water potential (Ψ), a composite physico-chemical variable reflecting the availability of water for biological processes such as plant growth and stomatal aperture. The Ψ of plant cells is mainly driven by their turgor and osmotic pressures. Here we investigated the effect of a variety of osmotic treatments on the roots of Arabidopsis plants grown in hydroponics. We used, among others, a permeating solute as a way to differentiate variations on turgor from variations in osmotic pressure. Measurement of cortical cell turgor pressure with a cell pressure probe allowed us to monitor the intensity of the treatments and thereby preserve the cortex from plasmolysis. Transcriptome analyses at an early time point (15 min) showed specific and quantitative transcriptomic responses to both osmotic and turgor pressure variations. Our results highlight how water-related biophysical parameters can shape the transcriptome of roots under stress and provide putative candidates to explore further the early perception of water stress in plants.

Genomic basis of multiphase evolution driving divergent selection of zinc-finger homeodomain genes

Gene families divergently evolve and become adapted as different genes with specific structures and functions in living organisms. We performed comprehensive structural and functional analyses of Zinc-finger homeodomain genes (ZF-HDs), including Mini zinc-finger genes (MIFs) and Zinc-finger with homeodomain genes (ZHDs), displaying competitive functions each other. Intensive annotation updates for 90 plant genomes verified that most MIFs (MIF-Is) exhibited distinct motif compositions from ZHDs, although some MIFs (MIF-Zs) contained ZHD-specific motifs. Phylogenetic analyses suggested that MIF-Zs and ZHDs originated from the same ancestral gene, whereas MIF-Is emerged from a distinct progenitor. We used a gene-editing system to identify a novel function of MIF-Is in rice: regulating the surface material patterns in anthers and pollen through transcriptional regulation by interacting ZHDs. Kingdom-wide investigations determined that (i) ancestral MIFs diverged into MIF-Is and MIF-Zs in the last universal common ancestor, (ii) integration of HD into the C-terminal of MIF-Zs created ZHDs after emergence of green plants and (iii) MIF-Is and ZHDs subsequently expanded independently into specific plant lineages, with additional formation of MIF-Zs from ZHDs. Our comprehensive analysis provides genomic evidence for multiphase evolution driving divergent selection of ZF-HDs.

The Mediator complex subunit MED25 interacts with HDA9 and PIF4 to regulate thermomorphogenesis

Thermomorphogenesis is, among other traits, characterized by enhanced hypocotyl elongation due to the induction of auxin biosynthesis genes like YUCCA8 by transcription factors, most notably PHYTOCHROME INTERACTING FACTOR 4 (PIF4). Efficient binding of PIF4 to the YUCCA8 locus under warmth depends on HISTONE DEACETYLASE 9 (HDA9) activity, which mediates histone H2A.Z depletion at the YUCCA8 locus. However, HDA9 lacks intrinsic DNA-binding capacity, and how HDA9 is recruited to YUCCA8, and possibly other PIF4-target sites, is currently not well understood. The Mediator complex functions as a bridge between transcription factors bound to specific promoter sequences and the basal transcription machinery containing RNA polymerase II. Mutants of Mediator component Mediator25 (MED25) exhibit reduced hypocotyl elongation and reduced expression of YUCCA8 at 27°C. In line with a proposed role for MED25 in thermomorphogenesis in Arabidopsis (Arabidopsis thaliana), we demonstrated an enhanced association of MED25 to the YUCCA8 locus under warmth and interaction of MED25 with both PIF4 and HDA9. Genetic analysis confirmed that MED25 and HDA9 operate in the same pathway. Intriguingly, we also showed that MED25 destabilizes HDA9 protein. Based on our findings, we propose that MED25 recruits HDA9 to the YUCCA8 locus by binding to both PIF4 and HDA9.

CRISPR-Cas engineering in food science and sustainable agriculture: recent advancements and applications

The developments in the food supply chain to support the growing population of the world is one of today's most pressing issues, and to achieve this goal improvements should be performed in both crops and microbes. For this purpose, novel approaches such as genome editing (GE) methods have upgraded the biological sciences for genome manipulation and, among such methods, clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) are the main exciting innovations since the Green Revolution. CRISPR/Cas systems can be a potent tool for the food industry, improvement of agricultural crops and even for protecting food-grade bacteria from foreign genetic invasive elements. This review introduces the history and mechanism of the CRISPR-Cas system as a genome editing tool and its applications in the vaccination of starter cultures, production of antimicrobials and bioactive compounds, and genome editing of microorganisms.

Interplay among ZF-HD and GRF transcription factors during Arabidopsis leaf development

The growth-regulating factor (GRF) family of transcriptional factors are involved in the control of leaf size and senescence, inflorescence and root growth, grain size, and plant regeneration. However, there is limited information about the genes regulated by these transcriptional factors, which are in turn responsible for their functions. Using a meta-analysis approach, we identified genes encoding Arabidopsis (Arabidopsis thaliana) zinc-finger homeodomain (ZF-HD) transcriptional factors, as potential targets of the GRFs. We further showed that GRF3 binds to the promoter of one of the members of the ZF-HD family, HOMEOBOX PROTEIN 33 (HB33), and activates its transcription. Increased levels of HB33 led to different modifications in leaf cell number and size that were dependent on its expression levels. Furthermore, we found that expression of HB33 for an extended period during leaf development increased leaf longevity. To cope with the functional redundancy among ZF-HD family members, we generated a dominant repressor version of HB33, HB33-SRDX. Expression of HB33-SRDX from HB33 regulatory regions was seedling-lethal, revealing the importance of the ZF-HD family in plant development. Misexpression of HB33-SRDX in early leaf development caused a reduction in both cell size and number. Interestingly, the loss-of-function of HB33 in lines carrying a GRF3 allele insensitive to miR396 reverted the delay in leaf senescence characteristic of these plants. Our results revealed functions for ZF-HDs in leaf development and linked them to the GRF pathway.

Mapping QTL for Phenological and Grain-Related Traits in a Mapping Population Derived from High-Zinc-Biofortified Wheat

Genomic regions governing days to heading (DH), days to maturity (DM), plant height (PH), thousand-kernel weight (TKW), and test weight (TW) were investigated in a set of 190 RILs derived from a cross between a widely cultivated wheat-variety, Kachu (DPW-621-50), and a high-zinc variety, Zinc-Shakti. The RIL population was genotyped using 909 DArTseq markers and phenotyped in three environments. The constructed genetic map had a total genetic length of 4665 cM, with an average marker density of 5.13 cM. A total of thirty-seven novel quantitative trait loci (QTL), including twelve for PH, six for DH, five for DM, eight for TKW and six for TW were identified. A set of 20 stable QTLs associated with the expression of DH, DM, PH, TKW, and TW were identified in two or more environments. Three novel pleiotropic genomic-regions harboring co-localized QTLs governing two or more traits were also identified. In silico analysis revealed that the DArTseq markers were located on important putative candidate genes such as MLO-like protein, Phytochrome, Zinc finger and RING-type, Cytochrome P450 and pentatricopeptide repeat, involved in the regulation of pollen maturity, the photoperiodic modulation of flowering-time, abiotic-stress tolerance, grain-filling duration, thousand-kernel weight, seed morphology, and plant growth and development. The identified novel QTLs, particularly stable and co-localized QTLs, will be validated to estimate their effects in different genetic backgrounds for subsequent use in marker-assisted selection (MAS).

Leaf rolling in bread wheat (Triticum aestivum L.) is controlled by the upregulation of a pair of closely linked/duplicate zinc finger homeodomain class transcription factors during moisture stress conditions

Zinc finger-homeodomain (ZF-HDs) class IV transcriptional factors (TFs) is a plant-specific transcription factor and play a key role in stress responses, plant growth, development, and hormonal signaling. In this study, two new leaf rolling TFs genes, namely TaZHD1 and TaZHD10, were identified in wheat using comparative genomic analysis of the target region that carried a major QTL for leaf rolling identified through multi-environment phenotyping and high throughput genotyping of a RIL population. Structural and functional annotation of the candidate ZHD genes with its closest rice orthologs reflects the species-specific evolution and, undoubtedly, validates the notions of remote-distance homology concept. Meanwhile, the morphological analysis resulted in contrasting difference for leaf rolling in extreme RILs between parental lines HD2012 and NI5439 at booting and heading stages. Transcriptome-wide expression profiling revealed that TaZHD10 transcripts showed significantly higher expression levels than TaZHD1 in all leaf tissues upon drought stress. The relative expression of these genes was further validated by qRT-PCR analysis, which also showed consistent results across the studied genotypes at the booting and anthesis stage. The contrasting modulation of these genes under drought conditions and the available evidenced for its epigenetic behavior that might involve the regulation of metabolic and gene regulatory networks. Prediction of miRNAs resulted in five Tae-miRs that could be associated with RNAi mediated control of TaZHD1 and TaZHD10 putatively involved in the metabolic pathway controlling rolled leaf phenotype. Gene interaction network analysis indicated that TaZHD1 and TaZHD10 showed pleiotropic effects and might also involve other functions in wheat in addition to leaf rolling. Overall, the results increase our understanding of TaZHD genes and provide valuable information as robust candidate genes for future functional genomics research aiming for the breeding of wheat varieties tolerant to leaf rolling.

Genome-Wide Identification and In Silico Analysis of ZF-HD Transcription Factor Genes in Zea mays L

Zinc finger-homeodomain proteins are amongst the most prominent transcription factors (TFs) involved in biological processes, such as growth, development, and morphogenesis, and assist plants in alleviating the adverse effects of abiotic and biotic stresses. In the present study, genome-wide identification and expression analyses of the maize ZHD gene family were conducted. A total of 21 ZHD genes with different physicochemical properties were found distributed on nine chromosomes in maize. Through sequence alignment and phylogenetic analysis, we divided ZHD proteins into eight groups that have variations in gene structure, motif distribution, and a conserved ZF domain. Synteny analysis indicated duplication in four pairs of genes and the presence of orthologues of maize in monocots. Ka/Ks ratios suggested that strong pure selection occurred during evolution. Expression profiling revealed that the genes are evenly expressed in different tissues. Most of the genes were found to make a contribution to abiotic stress response, plant growth, and development. Overall, the evolutionary research on exons and introns, motif distributions, and cis-acting regions suggests that these genes play distinct roles in biological processes which may provide a basis for further study of these genes' functions in other crops.

TANDEM ZINC-FINGER/PLUS3 regulates phytochrome B abundance and signaling to fine-tune hypocotyl growth

TANDEM ZINC-FINGER/PLUS3 (TZP) is a transcriptional regulator that acts at the crossroads of light and photoperiodic signaling. Here, we unveil a role for TZP in fine-tuning hypocotyl elongation under red light and long-day conditions. We provide genetic evidence for a synergistic action between TZP and PHOTOPERIODIC CONTROL OF HYPOCOTYL 1 (PCH1) in regulating the protein abundance of PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and downstream gene expression in response to red light and long days (LDs). Furthermore, we show that TZP is a positive regulator of the red/far-red light receptor and thermosensor phytochrome B (phyB) by promoting phyB protein abundance, nuclear body formation, and signaling. Our data therefore assign a function to TZP in regulating two key red light signaling components, phyB and PIF4, but also uncover a new role for PCH1 in regulating hypocotyl elongation in LDs. Our findings provide a framework for the understanding of the mechanisms associated with the TZP signal integration network and their importance for optimizing plant growth and adaptation to a changing environment.

CqZF-HD14 enhances drought tolerance in quinoa seedlings through interaction with CqHIPP34 and CqNAC79

Drought stress is a key agricultural problem that restricts plant development and crop yield. Research on quinoa (Chenopodium quinoa), a nutrient-rich crop with strong stress resistance, has been limited in terms of the molecular regulation of its adaptation to drought stress. This study identified the zinc finger-homeodomain (ZF-HD) family in quinoa and a drought-responsive Chenopodium quinoa ZF-HD14 (CqZF-HD14) through expression profiles. Transient overexpression of CqZF-HD14 promotes photosynthetic pigment accumulation under drought stress, strengthens the antioxidant system, and in turn enhances drought tolerance. Comprehensive genome-wide family analysis and expression profiling identified CqNAC79 and CqHIPP34 regulated by CqZF-HD14, and their interactions were further determined by bimolecular fluorescence complementation (BIFC). Moreover, physiological and biochemical analyses and transient overexpression also revealed that CqNAC79 and CqHIPP34 resist drought by promoting the accumulation of photosynthetic pigments and maintaining antioxidant capacity under drought stress. The synergistic effect of CqZF-HD14 with CqNAC79 or CqHIPP34 further enhanced the drought tolerance of quinoa seedlings. Taken together, the results indicate that CqZF-HD14, CqNAC79 and CqHIPP34 may be important contributors to the drought tolerance regulatory network in quinoa, and these findings add new members to the drought tolerance gene pool.

Class I TCP transcription factor AtTCP8 modulates key brassinosteroid-responsive genes

The plant-specific TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) transcription factor family is most closely associated with regulating plant developmental programs. Recently, TCPs were also shown to mediate host immune signaling, both as targets of pathogen virulence factors and as regulators of plant defense genes. However, comprehensive characterization of TCP gene targets is still lacking. Loss of function of the class I TCP gene AtTCP8 attenuates early immune signaling and, when combined with mutations in AtTCP14 and AtTCP15, additional layers of defense signaling in Arabidopsis (Arabidopsis thaliana). Here, we focus on TCP8, the most poorly characterized of the three to date. We used chromatin immunoprecipitation and RNA sequencing to identify TCP8-bound gene promoters and differentially regulated genes in the tcp8 mutant; these datasets were heavily enriched in signaling components for multiple phytohormone pathways, including brassinosteroids (BRs), auxin, and jasmonic acid. Using BR signaling as a representative example, we showed that TCP8 directly binds and activates the promoters of the key BR transcriptional regulatory genes BRASSINAZOLE-RESISTANT1 (BZR1) and BRASSINAZOLE-RESISTANT2 (BZR2/BES1). Furthermore, tcp8 mutant seedlings exhibited altered BR-responsive growth patterns and complementary reductions in BZR2 transcript levels, while TCP8 protein demonstrated BR-responsive changes in subnuclear localization and transcriptional activity. We conclude that one explanation for the substantial targeting of TCP8 alongside other TCP family members by pathogen effectors may lie in its role as a modulator of BR and other plant hormone signaling pathways.

Zinc Finger-Homeodomain and Mini Zinc Finger proteins are key players in plant growth and responses to environmental stresses

The ZINC FINGER-HOMEODOMAIN (ZHD) protein family is a plant-specific family of transcription factors containing two conserved motifs: a non-canonical C5H3 zinc finger domain (ZF) and a DNA-binding homeodomain (HD). The MINI ZINC FINGER (MIF) proteins belong to this family, but were possibly derived from the ZHDs by losing the HD. Information regarding the function of ZHD and MIF proteins is scarce. However, different studies have shown that ZHD/MIF proteins play important roles not only in plant growth and development, but also in response to environmental stresses, including drought and pathogen attack. Here we review recent advances relative to ZHD/MIF functions in multiple species, to provide new insights into the diverse roles of these transcription factors in plants. Their mechanism of action in relation to their ability to interact with other proteins and DNA is also discussed. We then propose directions for future studies to understand better their important roles and pinpoint strategies for potential applications in crop improvement.

Low Fluence Ultraviolet-B Promotes Ultraviolet Resistance 8-Modulated Flowering in Arabidopsis

Ultraviolet-B (UV-B) irradiation (280-320 nm) is an integral part of sunlight and a pivotal environmental cue that triggers various plant responses, from photoprotection to photomorphogenesis and metabolic processes. UV-B is perceived by ULTRAVIOLET RESISTANCE 8 (UVR8), which orchestrates UV-B signal transduction and transcriptional control of UV-B-responsive genes. However, there is limited information on the molecular mechanism underlying the UV-B- and UVR8-dependent regulation of flowering time in plants. Here, we investigate the role of UV-B and UVR8 in photoperiodic flowering in Arabidopsis thaliana. Our findings suggest that UV-B controls photoperiodic flowering in an ecotype-specific manner and that UVR8 acts as a negative regulator of UV-B-induced flowering. Overall, our research shows that UV-B modulates flowering initiation through the action of UVR8 at the transcriptional level.

Interactome of Arabidopsis Thaliana

More than 95,000 protein–protein interactions of Arabidopsis thaliana have been published and deposited in databases. This dataset was supplemented by approximately 900 additional interactions, which were identified in the literature from the years 2002–2021. These protein–protein interactions were used as the basis for a Cytoscape network and were supplemented with data on subcellular localization, gene ontologies, biochemical properties and co-expression. The resulting network has been exemplarily applied in unraveling the PPI-network of the plant vacuolar proton-translocating ATPase (V-ATPase), which was selected due to its central importance for the plant cell. In particular, it is involved in cellular pH homeostasis, providing proton motive force necessary for transport processes, trafficking of proteins and, thereby, cell wall synthesis. The data points to regulation taking place on multiple levels: (a) a phosphorylation-dependent regulation by 14-3-3 proteins and by kinases such as WNK8 and NDPK1a, (b) an energy-dependent regulation via HXK1 and the glucose receptor RGS1 and (c) a Ca2+-dependent regulation by SOS2 and IDQ6. The known importance of V-ATPase for cell wall synthesis is supported by its interactions with several proteins involved in cell wall synthesis. The resulting network was further analyzed for (experimental) biases and was found to be enriched in nuclear, cytosolic and plasma membrane proteins but depleted in extracellular and mitochondrial proteins, in comparison to the entity of protein-coding genes. Among the processes and functions, proteins involved in transcription were highly abundant in the network. Subnetworks were extracted for organelles, processes and protein families. The degree of representation of organelles and processes reveals limitations and advantages in the current knowledge of protein–protein interactions, which have been mainly caused by a high number of database entries being contributed by only a few publications with highly specific motivations and methodologies that favor, for instance, interactions in the cytosol and the nucleus.

Mutual upregulation of HY5 and TZP in mediating phytochrome A signaling

Phytochrome A (phyA) is the far-red (FR) light photoreceptor in plants that is essential for seedling de-etiolation under FR-rich environments, such as canopy shade. TANDEM ZINC-FINGER/PLUS3 (TZP) was recently identified as a key component of phyA signal transduction in Arabidopsis thaliana; however, how TZP is integrated into the phyA signaling networks remains largely obscure. Here, we demonstrate that ELONGATED HYPOCOTYL5 (HY5), a well-characterized transcription factor promoting photomorphogenesis, mediates FR light induction of TZP expression by directly binding to a G-box motif in the TZP promoter. Furthermore, TZP physically interacts with CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1), an E3 ubiquitin ligase targeting HY5 for 26S proteasome-mediated degradation, and this interaction inhibits COP1 interaction with HY5. Consistent with those results, TZP post-translationally promotes HY5 protein stability in FR light, and in turn, TZP protein itself is destabilized by COP1 in both dark and FR light conditions. Moreover, tzp hy5 double mutants display an additive phenotype relative to their respective single mutants under high FR light intensities, indicating that TZP and HY5 also function in largely independent pathways. Together, our data demonstrate that HY5 and TZP mutually upregulate each other in transmitting the FR light signal, thus providing insights into the complicated but delicate control of phyA signaling networks.

Functional characterization of Lilium lancifolium cold-responsive Zinc Finger Homeodomain (ZFHD) gene in abscisic acid and osmotic stress tolerance

Background.

We have previously performed an analysis of the cold-responsive transcriptome in the mature leaves of tiger lily (Lilium lancifolium) by gene co-expression network identification. The results has revealed that a ZFHD gene, notated as encoding zinc finger homeodomain protein, may play an essential regulating role in tiger lily response to cold stress.

Methods.

A further investigation of the ZFHD gene (termed as LlZFHD4) responding to osmotic stresses, including cold, salt, water stresses, and abscisic acid (ABA) was performed in this study. Based on the transcriptome sequences, the coding region and 5′ promoter region of LlZFHD4 were cloned from mature tiger lily leaves. Stress response analysis was performed under continuous 4 °C, NaCl, PEG, and ABA treatments. Functional characterization of LlZFHD4 was conducted in transgenic Arabidopsis, tobacco, and yeast.

Results.

LlZFHD4 encodes a nuclear-localized protein consisting of 180 amino acids. The N-terminal region of LlZFHD4 has transcriptional activation activity in yeast. The 4 °C, NaCl, PEG, and ABA treatments induced the expression of LlZFHD4. Several stress- or hormone-responsive cis-acting regulatory elements (T-Box, BoxI. and ARF) and binding sites of transcription factors (MYC, DRE and W-box) were found in the core promoter region (789 bp) of LlZFHD4. Also, the GUS gene driven by LlZFHD4 promoter was up-regulated by cold, NaCl, water stresses, and ABA in Arabidopsis. Overexpression of LlZFHD4 improved cold and drought tolerance in transgenic Arabidopsis; higher survival rate and better osmotic adjustment capacity were observed in LlZFHD4 transgenic plants compared to wild type (WT) plants under 4 °C and PEG conditions. However, LlZFHD4 transgenic plants were less tolerant to salinity and more hypersensitive to ABA compared to WT plants. The transcript levels of stress- and ABA-responsive genes were much more up-regulated in LlZFHD4 transgenic Arabidopsis than WT. These results indicate LlZFHD4 is involved in ABA signaling pathway and plays a crucial role in regulating the response of tiger lily to cold, salt and water stresses.

Zinc oxide nanoparticles and 24-epibrassinolide alleviates Cu toxicity in tomato by regulating ROS scavenging, stomatal movement and photosynthesis

Nanoparticles (NPs) have recently emerged as potential agents for plants to ameliorate abiotic stresses by acting as nano-fertilizers. In this regard, the influence of the zinc oxide nanoparticles (ZnO-NPs) on plant responses to copper (Cu) stress has been poorly understood. Hence, the present study was executed to explore the role of ZnO-NPs (foliar) and 24-epibrassinolide (EBL; root dipping) individually or in combined form in the resilience of tomato (Solanum lycopersicum) plant to Cu stress. Tomato seeds were sown to make the nursery; and at 20 days after sowing (DAS) the plantlets were submerged in 10-8 M of EBL solution for 2 h, and subsequently transplanted in the soil-filled earthen pots. Cu concentration (100 mg kg-1) was applied to the soil at 30 DAS, whereas at 35 DAS plants were sprinkled with double distilled water (DDW; control), 50 mg/L of Zinc (Zn) and 50 mg/L of ZnO-NPs; and plant performance were evaluated at 45 DAS. It was evident that Cu-stress reduced photosynthesis (17.3%), stomatal conductance (18.1%), plant height (19.7%), and nitrate reductase (NR) activity (19.2%), but increased malondialdehyde (MDA; 29.4%), superoxide radical (O2-; 22.3%) and hydrogen peroxide (H2O2; 26.2%) content in S. lycopersicum. Moreover, ZnO-NPs and/or EBL implemented via different modes improved photosynthetic activity, stomatal aperture, growth, cell viability and activity of antioxidant enzymes and proline that augmented resilience of tomato plants to Cu stress. These observations depicted that application of ZnO-NPs and EBL could be a useful approach to assist Cu confiscation and stress tolerance against Cu in tomato plants grown in Cu contaminated sites.

Metabolic control of histone demethylase activity involved in plant response to high temperature

Jumonji C (JmjC) domain proteins are histone lysine demethylases that require ferrous iron and alpha-ketoglutarate (or α-KG) as cofactors in the oxidative demethylation reaction. In plants, α-KG is produced by isocitrate dehydrogenases (ICDHs) in different metabolic pathways. It remains unclear whether fluctuation of α-KG levels affects JmjC demethylase activity and epigenetic regulation of plant gene expression. In this work, we studied the impact of loss of function of the cytosolic ICDH (cICDH) gene on the function of histone demethylases in Arabidopsis thaliana. Loss of cICDH resulted in increases of overall histone H3 lysine 4 trimethylation (H3K4me3) and enhanced mutation defects of the H3K4me3 demethylase gene JMJ14. Genetic analysis suggested that the cICDH mutation may affect the activity of other demethylases, including JMJ15 and JMJ18 that function redundantly with JMJ14 in the plant thermosensory response. Furthermore, we show that mutation of JMJ14 affected both the gene activation and repression programs of the plant thermosensory response and that JMJ14 and JMJ15 repressed a set of genes that are likely to play negative roles in the process. The results provide evidence that histone H3K4 demethylases are involved in the plant response to elevated ambient temperature.

Zinc Finger-Homeodomain Transcriptional Factors (ZF-HDs) in Wheat (Triticum aestivum L.): Identification, Evolution, Expression Analysis and Response to Abiotic Stresses

Zinc finger-homeodomain transcriptional factors (ZF-HDs), a kind of plant-specific transcription factor, play important roles in plant growth, development and various stress responses. In this study, the genome-wide analysis of the ZF-HD gene family was performed in wheat. A total of 37 TaZF-HD genes were identified in T. aestivum and classified into six groups. The results of a synteny analysis showed that gene replication events contributed to the expansion of the TaZF-HD gene family. The TaZF-HD paralogous gene pairs with similar chromosomal locations in different subgenomes had similar expression patterns. TaZF-HDs were highly induced under PEG (polyethylene glycol), NaCl and cold stress but not induced under heat stress. Gene ontology (GO) annotation and protein-protein interactions suggested that TaZF-HD proteins may participate in various biological processes of plants. These results increase our understanding of ZF-HD genes and provide robust candidate genes for future functional investigations aimed at crop improvement.

HBI1 acts downstream of ERECTA and SWR1 in regulating inflorescence architecture through the activation of the brassinosteroid and auxin signaling pathways

Inflorescence architecture critically influences plant reproductive success and crop yield, and it reflects the activity of the inflorescence meristem and pedicel length. In Arabidopsis thaliana, the ERECTA (ER) signaling pathway and the SWR1 chromatin remodeling complex jointly regulate inflorescence architecture by promoting the expression of the PACLOBUTRAZOL RESISTANCE (PRE) gene family. However, how PREs regulate inflorescence architecture remains unclear. RNA-sequencing and chromatin immunoprecipitation coupled with quantitative PCR analyses were performed. Genetic interactions between HOMOLOG OF BEE2 INTERACTING WITH IBH1 (HBI1) and the SWR1-ER-MPK6 pathway in the control of inflorescence architecture were further studied. The present findings support that HBI1 functions downstream of PREs in the SWR1 and ER pathways to regulate inflorescence architecture by promoting pedicel elongation. Specifically, it binds to the promoters of the brassinosteroid (BR) biosynthesis gene CYP85A2 and a series of auxin-related genes, including auxin response factor ARF3, and promotes their expression. In turn, ARF3 can also bind to auxin signaling genes as well as CYP85A2 to activate their expression and promote pedicel elongation. Our study provides evidence that inflorescence architecture regulation by SWR1 and ER involves the HBI1 regulatory hub and its activation of both the BR and auxin hormone pathways.

HISTONE DEACETYLASE 9 stimulates auxin-dependent thermomorphogenesis in Arabidopsis thaliana by mediating H2A.Z depletion

Many plant species respond to unfavorable high ambient temperatures by adjusting their vegetative body plan to facilitate cooling. This process is known as thermomorphogenesis and is induced by the phytohormone auxin. Here, we demonstrate that the chromatin-modifying enzyme HISTONE DEACETYLASE 9 (HDA9) mediates thermomorphogenesis but does not interfere with hypocotyl elongation during shade avoidance. HDA9 is stabilized in response to high temperature and mediates histone deacetylation at the YUCCA8 locus, a rate-limiting enzyme in auxin biosynthesis, at warm temperatures. We show that HDA9 permits net eviction of the H2A.Z histone variant from nucleosomes associated with YUCCA8, allowing binding and transcriptional activation by PHYTOCHROME INTERACTING FACTOR 4, followed by auxin accumulation and thermomorphogenesis.

METTL3-mediated N6-methyladenosine modification is critical for epithelial-mesenchymal transition and metastasis of gastric cancer

BACKGROUND

As one of the most frequent chemical modifications in eukaryotic mRNAs, N6-methyladenosine (m6A) modification exerts important effects on mRNA stability, splicing, and translation. Recently, the regulatory role of m6A in tumorigenesis has been increasingly recognized. However, dysregulation of m6A and its functions in tumor epithelial-mesenchymal transition (EMT) and metastasis remain obscure.

METHODS

qRT-PCR and immunohistochemistry were used to evaluate the expression of methyltransferase-like 3 (METTL3) in gastric cancer (GC). The effects of METTL3 on GC metastasis were investigated through in vitro and in vivo assays. The mechanism of METTL3 action was explored through transcriptome-sequencing, m6A-sequencing, m6A methylated RNA immunoprecipitation quantitative reverse transcription polymerase chain reaction (MeRIP qRT-PCR), confocal immunofluorescent assay, luciferase reporter assay, co-immunoprecipitation, RNA immunoprecipitation and chromatin immunoprecipitation assay.

RESULTS

Here, we show that METTL3, a major RNA N6-adenosine methyltransferase, was upregulated in GC. Clinically, elevated METTL3 level was predictive of poor prognosis. Functionally, we found that METTL3 was required for the EMT process in vitro and for metastasis in vivo. Mechanistically, we unveiled the METTL3-mediated m6A modification profile in GC cells for the first time and identified zinc finger MYM-type containing 1 (ZMYM1) as a bona fide m6A target of METTL3. The m6A modification of ZMYM1 mRNA by METTL3 enhanced its stability relying on the "reader" protein HuR (also known as ELAVL1) dependent pathway. In addition, ZMYM1 bound to and mediated the repression of E-cadherin promoter by recruiting the CtBP/LSD1/CoREST complex, thus facilitating the EMT program and metastasis.

CONCLUSIONS

Collectively, our findings indicate the critical role of m6A modification in GC and uncover METTL3/ZMYM1/E-cadherin signaling as a potential therapeutic target in anti-metastatic strategy against GC.

Direct Regulation of the EFR-Dependent Immune Response by Arabidopsis TCP Transcription Factors

One layer of the innate immune system allows plants to recognize pathogen-associated molecular patterns (PAMPS), activating a defense response known as PAMP-triggered immunity (PTI). Maintaining an active immune response, however, comes at the cost of plant growth and development; accordingly, optimization of the balance between defense and development is critical to plant fitness. The TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) transcription factor family consists of well-characterized transcriptional regulators of plant development and morphogenesis. The three closely related class I TCP transcription factors TCP8, TCP14, and TCP15 have also been implicated in the regulation of effector-triggered immunity, but there has been no previous characterization of PTI-related phenotypes. To identify TCP targets involved in PTI, we screened a PAMP-induced gene promoter library in a yeast one-hybrid assay and identified interactions of these three TCPs with the EF-Tu RECEPTOR (EFR) promoter. The direct interactions between TCP8 and EFR were confirmed to require an intact TCP binding site in planta. A tcp8 tcp14 tcp15 triple mutant was impaired in EFR-dependent PTI and exhibited reduced levels of PATHOGENESIS-RELATED PROTEIN 2 and induction of EFR expression after elicitation with elf18 but also increased production of reactive oxygen species relative to Col-0. Our data support an increasingly complex role for TCPs at the nexus of plant development and defense.

Light and temperature shape nuclear architecture and gene expression

Environmental stimuli play a major role in modulating growth and development throughout the life-cycle of a plant. Quantitative and qualitative variations in light and temperature trigger changes in gene expression that ultimately shape plant morphology for adaptation and survival. Although the phenotypic and transcriptomic basis of plant responses to the constantly changing environment have been examined for decades, the relationship between global changes in nuclear architecture and adaption to environmental stimuli is just being uncovered. This review presents recent discoveries investigating how changes in light and temperature trigger changes in chromatin structure and nuclear organization with a focus on the role of gene repositioning and chromatin accessibility in regulating gene expression.