Genome-wide analysis of CCCH zinc finger family in Arabidopsis and rice

Two transcription factors, RhERF005 and RhCCCH12, regulate rose resistance to Botrytis cinerea by modulating cytokinin levels

Gray mold caused by the necrotrophic fungal pathogen Botrytis cinerea is one of the most destructive diseases in rose (Rosa spp.). Rose infection by B. cinerea leads to severe economic losses due to necrosis, tissue collapse, and rot. In rose, cytokinins (CKs) positively regulate a defense response to B. cinerea, but little is known about the underlying molecular mechanisms. Here, we characterized two ethylene/jasmonic acid-regulated transcription factors, RhEFR005 and RhCCCH12, that bind to the promoter region of PATHOGENESIS-RELATED 10.1 (RhPR10.1) and promote its transcription, leading to decreased susceptibility to B. cinerea. The RhEFR005/RhCCCH12-RhPR10.1 module regulated cytokinin content in rose, and the susceptibility of RhEFR005-, RhCCCH12-, and RhPR10.1-silenced rose petals can be rescued by exogenous CK. In summary, our results reveal that the RhERF005/RhCCCH12-RhPR10.1 module regulates the CK-induced defense response of rose to B. cinerea.

A Case Study from the Overexpression of OsTZF5, Encoding a CCCH Tandem Zinc Finger Protein, in Rice Plants Across Nineteen Yield Trials

BACKGROUND

Development of transgenic rice overexpressing transcription factors involved in drought response has been previously reported to confer drought tolerance and therefore represents a means of crop improvement. We transformed lowland rice IR64 with OsTZF5, encoding a CCCH-tandem zinc finger protein, under the control of the rice LIP9 stress-inducible promoter and compared the drought response of transgenic lines and nulls to IR64 in successive screenhouse paddy and field trials up to the T6 generation.

RESULTS

Compared to the well-watered conditions, the level of drought stress across experiments varied from a minimum of - 25 to - 75 kPa at a soil depth of 30 cm which reduced biomass by 30-55% and grain yield by 1-92%, presenting a range of drought severities. OsTZF5 transgenic lines showed high yield advantage under drought over IR64 in early generations, which was related to shorter time to flowering, lower shoot biomass and higher harvest index. However, the increases in values for yield and related traits in the transgenics became smaller over successive generations despite continued detection of drought-induced transgene expression as conferred by the LIP9 promoter. The decreased advantage of the transgenics over generations tended to coincide with increased levels of homozygosity. Background cleaning of the transgenic lines as well as introgression of the transgene into an IR64 line containing major-effect drought yield QTLs, which were evaluated starting at the BC3F1 and BC2F3 generation, respectively, did not result in consistently increased yield under drought as compared to the respective checks.

CONCLUSIONS

Although we cannot conclusively explain the genetic factors behind the loss of yield advantage of the transgenics under drought across generations, our results help in distinguishing among potential drought tolerance mechanisms related to effectiveness of the transgenics, since early flowering and harvest index most closely reflected the levels of yield advantage in the transgenics across generations while reduced biomass did not.

Transcriptomic Analyses Reveal Insights into the Shared Regulatory Network of Phenolic Compounds and Steviol Glycosides in Stevia rebaudiana

Stevia rebaudiana (Bertoni) is a highly valuable crop for the steviol glycoside content in its leaves, which are no-calorie sweeteners hundreds of times more potent than sucrose. The presence of health-promoting phenolic compounds, particularly flavonoids, in the leaf of S. rebaudiana adds further nutritional value to this crop. Although all these secondary metabolites are highly desirable in S. rebaudiana leaves, the genes regulating the biosynthesis of phenolic compounds and the shared gene network between the regulation of biosynthesis of steviol glycosides and phenolic compounds still need to be investigated in this species. To identify putative candidate genes involved in the synergistic regulation of steviol glycosides and phenolic compounds, four genotypes with different contents of these compounds were selected for a pairwise comparison RNA-seq analysis, yielding 1136 differentially expressed genes. Genes that highly correlate with both steviol glycosides and phenolic compound accumulation in the four genotypes of S. rebaudiana were identified using the weighted gene co-expression network analysis. The presence of UDP-glycosyltransferases 76G1, 76H1, 85C1, and 91A1, and several genes associated with the phenylpropanoid pathway, including peroxidase, caffeoyl-CoA O-methyltransferase, and malonyl-coenzyme A:anthocyanin 3-O-glucoside-6″-O-malonyltransferase, along with 21 transcription factors like SCL3, WRK11, and MYB111, implied an extensive and synergistic regulatory network involved in enhancing the production of such compounds in S. rebaudiana leaves. In conclusion, this work identified a variety of putative candidate genes involved in the biosynthesis and regulation of particular steviol glycosides and phenolic compounds that will be useful in gene editing strategies for increasing and steering the production of such compounds in S. rebaudiana as well as in other species.

Heterologous Expression of Two Brassica campestris CCCH Zinc-Finger Proteins in Arabidopsis Induces Cytoplasmic Foci and Causes Pollen Abortion

The membrane-less organelles in cytoplasm that are presented as cytoplasmic foci were successively identified. Although multiple CCCH zinc-finger proteins have been found to be localized in cytoplasmic foci, the relationship between their specific localization and functions still needs further clarification. Here, we report that the heterologous expression of two Brassica campestris CCCH zinc-finger protein genes (BcMF30a and BcMF30c) in Arabidopsis thaliana can affect microgametogenesis by involving the formation of cytoplasmic foci. By monitoring the distribution of proteins and observing pollen phenotypes, we found that, when these two proteins were moderately expressed in pollen, they were mainly dispersed in the cytoplasm, and the pollen developed normally. However, high expression induced the assembly of cytoplasmic foci, leading to pollen abortion. These findings suggested that the continuous formation of BcMF30a/BcMF30c-associated cytoplasmic foci due to high expression was the inducement of male sterility. A co-localization analysis further showed that these two proteins can be recruited into two well-studied cytoplasmic foci, processing bodies (PBs), and stress granules (SGs), which were confirmed to function in mRNA metabolism. Together, our data suggested that BcMF30a and BcMF30c play component roles in the assembly of pollen cytoplasmic foci. Combined with our previous study on the homologous gene of BcMF30a/c in Arabidopsis, we concluded that the function of these homologous genes is conserved and that cytoplasmic foci containing BcMF30a/c may participate in the regulation of gene expression in pollen by regulating mRNA metabolism.

CRISPR/Cas9 mutagenesis of the Arabidopsis GROWTH-REGULATING FACTOR (GRF) gene family

Genome editing in plants typically relies on T-DNA plasmids that are mobilized by Agrobacterium-mediated transformation to deliver the CRISPR/Cas machinery. Here, we introduce a series of CRISPR/Cas9 T-DNA vectors for minimal settings, such as teaching labs. Gene-specific targeting sequences can be inserted as annealed short oligonucleotides in a single straightforward cloning step. Fluorescent markers expressed in mature seeds enable reliable selection of transgenic or transgene-free individuals using a combination of inexpensive LED lamps and colored-glass alternative filters. Testing these tools on the Arabidopsis GROWTH-REGULATING FACTOR (GRF) genes, we were able to create a collection of predicted null mutations in all nine family members with little effort. We then explored the effects of simultaneously targeting two, four and eight GRF genes on the rate of induced mutations at each target locus. In our hands, multiplexing was associated with pronounced disparities: while mutation rates at some loci remained consistently high, mutation rates at other loci dropped dramatically with increasing number of single guide RNA species, thereby preventing a systematic mutagenesis of the family.

Floral Development on Vitis vinifera Is Associated with MADS-Box Transcription Factors through the Transcriptional Regulation of VviZIP3

Several grapevine (Vitis vinifera L.) cultivars show a tendency to develop parthenocarpic seedless grapes, affecting fruit yield and quality. This reproductive disorder originates in defective ovule fertilization due to a failure in pollen tube growth. Zinc (Zn) is a crucial trace element, playing a vital role in various physiological and metabolic processes. It is particularly essential for the healthy growth of flowers and fruits. Insufficient zinc has been suggested as a potential reason for issues in this development process. This microelement is taken up through a mechanism that involves transporters, including the ZRT-IRT-like protein (ZIP) gene family, associated with the influx of Zn into the cell. In grapevines, 20 genes for ZIP-type transporters have been described. In this study, we analyzed the expression pattern of VviZIP3 during flower development and employ transgenic methods to assess its transcriptional regulation. Furthermore, through computational examination of the promoter region, we identified two CArG boxes, recognized as responsive elements to MADS transcription factors. These factors play a key role in shaping various components of a flower, such as pollen. Our investigation of the VviZIP3 promoter confirms the functionality of these CArG boxes. Overall, our results suggest that the increased expression of VviZIP3 during flowering is likely under the influence of MADS transcription factors.

Identification of CCCH-type zinc finger antiviral protein 1 (ZAP) gene from Pacific white shrimp (Penaeus vannamei): Characterization and expression analysis in response to viral infection

Zinc-finger proteins (ZFPs) are a huge family that exert multiple roles in the cells. ZFPs could be divided into nine types based on the numbers and positions of conserved Cys and His residues, in which CCCH-type ZFP was one of the most widely studied types. CCCH-type zinc finger antiviral protein 1 (ZAP), a CCCH-type ZFP that can inhibit the replication of certain RNA viruses and DNA viruses by mediating degradation of viral RNA and repressing mRNA translation, plays significant roles in the host innate immune defenses against viral infections. Presently, there have been numerous reports investigating the antiviral ability of ZAP, while no data is available about ZAP gene in the species of shrimps or even crustaceans. In this study, a novel protein containing CCCH-type zinc finger motifs (ZnF-CCCH), CCCH-type zinc finger antiviral protein 1 (ZAP) gene, was identified from Pacific white shrimp (Penaeus vannamei) and its role in antiviral immunity was further investigated. Similar to mammalian ZAPs, in addition to ZnF-CCCH, PvZAP also possesses central WWE domains and C-terminal PARP domain. Phylogenetic analysis showed that PvZAP was close to that of the crustacean Pacific oyster, separating from the cluster of vertebrate ZAP proteins. Upon in vivo infection by IHHNV, gene expression of PvZAP was strongly up-regulated in the hepatopancreas and gills of both adult and juvenile shrimps, where adult individuals showed higher fold changes of up-regulation than in juvenile individuals. These results suggested that PvZAP might play an important role in the innate immune defense of Pacific white shrimp against IHHNV infection. This allows us to gain new insights into the immunological function of ZAP in the innate immunity of shrimp species and even crustaceans.

Genome-Wide Identification and Expression Analysis of C3H Zinc Finger Family in Potato (Solanum tuberosum L.)

Transcription factors containing a CCCH structure (C3H) play important roles in plant growth and development, and their stress response, but research on the C3H gene family in potato has not been reported yet. In this study, we used bioinformatics to identify 50 C3H genes in potato and named them StC3H-1 to StC3H-50 according to their location on chromosomes, and we analyzed their physical and chemical properties, chromosome location, phylogenetic relationship, gene structure, collinearity relationship, and cis-regulatory element. The gene expression pattern analysis showed that many StC3H genes are involved in potato growth and development, and their response to diverse environmental stresses. Furthermore, RT-qPCR data showed that the expression of many StC3H genes was induced by high temperatures, indicating that StC3H genes may play important roles in potato response to heat stress. In addition, Some StC3H genes were predominantly expressed in the stolon and developing tubers, suggesting that these StC3H genes may be involved in the regulation of tuber development. Together, these results provide new information on StC3H genes and will be helpful for further revealing the function of StC3H genes in the heat stress response and tuber development in potato.

A LlMYB305-LlC3H18-LlWRKY33 module regulates thermotolerance in lily

The CCCH proteins play important roles in plant growth and development, hormone response, pathogen defense and abiotic stress tolerance. However, the knowledge of their roles in thermotolerance are scarce. Here, we identified a heat-inducible CCCH gene LlC3H18 from lily. LlC3H18 was localized in the cytoplasm and nucleus under normal conditions, while it translocated in the cytoplasmic foci and co-located with the markers of two messenger ribonucleoprotein (mRNP) granules, processing bodies (PBs) and stress granules (SGs) under heat stress conditions, and it also exhibited RNA-binding ability. In addition, LlC3H18 exhibited transactivation activity in both yeast and plant cells. In lily and Arabidopsis, overexpression of LlC3H18 damaged their thermotolerances, and silencing of LlC3H18 in lily also impaired its thermotolerance. Similarly, Arabidopsis atc3h18 mutant also showed decreased thermotolerance. These results indicated that the appropriate expression of C3H18 was crucial for establishing thermotolerance. Further analysis found that LlC3H18 directly bound to the promoter of LlWRKY33 and activated its expression. Besides, it was found that LlMYB305 acted as an upstream factor of LlC3H18 and activated its expression. In conclusion, we demonstrated that there may be a LlMYB305-LlC3H18-LlWRKY33 regulatory module in lily that is involved in the establishment of thermotolerance and finely regulates heat stress response.

GhbZIP30-GhCCCH17 module accelerates corm dormancy release by reducing endogenous ABA under cold storage in Gladiolus

Gladiolus hybridus is one of the most popular flowers worldwide. However, its corm dormancy characteristic largely limits its off-season production. Long-term cold treatment (LT), which increases sugar content and reduces abscisic acid (ABA), is an efficient approach to accelerate corm dormancy release (CDR). Here, we identified a GhbZIP30-GhCCCH17 module that mediates the antagonism between sugars and ABA during CDR. We showed that sugars promoted CDR by reducing ABA levels in Gladiolus. Our data demonstrated that GhbZIP30 transcription factor directly binds the GhCCCH17 zinc finger promoter and activates its transcription, confirmed by yeast one-hybrid, dual-luciferase (Dual-LUC), chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) and electrophoretic mobility shift assay (EMSA). GhCCCH17 is a transcriptional activator, and its nuclear localisation is altered by glucose and cytokinin treatments. Both GhbZIP30 and GhCCCH17 positively respond to LT, sugars, and cytokinin treatments. Silencing GhbZIP30 or GhCCCH17 resulted in delayed CDR by regulating ABA metabolic genes, while their overexpression promoted CDR. Taken together, we propose that the GhbZIP30-GhCCCH17 module is involved in cold- and glucose-induced CDR by regulating ABA metabolic genes.

Functional characterization of TBL genes revealed the role of GhTBL7 and GhTBL58 in cotton fiber elongation

TBL (Trichome Birefringence Like) gene family members are involved in trichome initiation and xylan acetylation in several plant species. In our research, we identified 102 TBLs from G. hirsutum. The phylogenetic tree classified TBL genes into five groups. Collinearity analysis of TBL genes indicated 136 paralogous gene pairs in G. hirsutum. Gene duplication indicated that WGD or segmental duplication contributed to the GhTBL gene family expansion. Promoter cis-elements of GhTBLs were related to growth and development, seed-specific regulation, light, and stress responses. GhTBL genes (GhTBL7, GhTBL15, GhTBL21, GhTBL25, GhTBL45, GhTBL54, GhTBL67, GhTBL72, and GhTBL77) exhibited upregulated response under exposure to cold, heat, NaCl, and PEG. GhTBL genes exhibited high expression during fiber development stages. Two GhTBL genes (GhTBL7 and GhTBL58) showed differential expression at 10 DPA fiber, as 10 DPA is a fast fiber elongation stage and fiber elongation is a very important stage of cotton fiber development. Subcellular localization of GhTBL7 and GhTBL58 revealed that these genes reside inside the cell membrane. Promoter GUS activity of GhTBL7 and GhTBL58 exhibited deep staining in roots. To further validate the role of these genes in cotton fiber elongation, we silenced these genes and observed a significant reduction in the fiber length at 10 DPA. In conclusion, the functional study of cell membrane-associated genes (GhTBL7 and GhTBL58) showed deep staining in root tissues and potential function during cotton fiber elongation at 10 DPA fiber.

A molecular framework underlying low-nitrogen-induced early leaf senescence in Arabidopsis thaliana

Nitrogen (N) deficiency causes early leaf senescence, resulting in accelerated whole-plant maturation and severely reduced crop yield. However, the molecular mechanisms underlying N-deficiency-induced early leaf senescence remain unclear, even in the model species Arabidopsis thaliana. In this study, we identified Growth, Development and Splicing 1 (GDS1), a previously reported transcription factor, as a new regulator of nitrate (NO₃^-) signaling by a yeast-one-hybrid screen using a NO₃^- enhancer fragment from the promoter of NRT2.1. We showed that GDS1 promotes NO₃^- signaling, absorption and assimilation by affecting the expression of multiple NO₃^- regulatory genes, including Nitrate Regulatory Gene2 (NRG2). Interestingly, we observed that gds1 mutants show early leaf senescence as well as reduced NO₃^- content and N uptake under N-deficient conditions. Further analyses indicated that GDS1 binds to the promoters of several senescence-related genes, including Phytochrome-Interacting Transcription Factors 4 and 5 (PIF4 and PIF5) and represses their expression. Interestingly, we found that N deficiency decreases GDS1 protein accumulation, and GDS1 could interact with Anaphase Promoting Complex Subunit 10 (APC10). Genetic and biochemical experiments demonstrated that Anaphase Promoting Complex or Cyclosome (APC/C) promotes the ubiquitination and degradation of GDS1 under N deficiency, resulting in loss of PIF4 and PIF5 repression and consequent early leaf senescence. Furthermore, we discovered that overexpression of GDS1 could delay leaf senescence and improve seed yield and N-use efficiency (NUE) in Arabidopsis. In summary, our study uncovers a molecular framework illustrating a new mechanism underlying low-N-induced early leaf senescence and provides potential targets for genetic improvement of crop varieties with increased yield and NUE.

Genomic Identification of CCCH-Type Zinc Finger Protein Genes Reveals the Role of HuTZF3 in Tolerance of Heat and Salt Stress of Pitaya (Hylocereus polyrhizus)

Pitaya (Hylocereus polyrhizus) is cultivated in a broad ecological range, due to its tolerance to drought, heat, and poor soil. The zinc finger proteins regulate gene expression at the transcriptional and post-transcriptional levels, by interacting with DNA, RNA, and proteins, to play roles in plant growth and development, and stress response. Here, a total of 81 CCCH-type zinc finger protein genes were identified from the pitaya genome. Transcriptomic analysis showed that nine of them, including HuTZF3, responded to both salt and heat stress. RT-qPCR results showed that HuTZF3 is expressed in all tested organs of pitaya, with a high level in the roots and stems, and confirmed that expression of HuTZF3 is induced by salt and heat stress. Subcellular localization showed that HuTZF3 is targeted in the processing bodies (PBs) and stress granules (SGs). Heterologous expression of HuTZF3 could improve both salt and heat tolerance in Arabidopsis, reduce oxidative stress, and improve the activity of catalase and peroxidase. Therefore, HuTZF3 may be involved in post-transcriptional regulation via localizing to PBs and SGs, contributing to both salt and heat tolerance in pitaya.

SPINDLY O-fucosylates nuclear and cytoplasmic proteins involved in diverse cellular processes in plants

SPINDLY (SPY) is a novel nucleocytoplasmic protein O-fucosyltransferase that regulates target protein activity or stability via O-fucosylation of specific Ser/Thr residues. Previous genetic studies indicate that AtSPY regulates plant development during vegetative and reproductive growth by modulating gibberellin and cytokinin responses. AtSPY also regulates the circadian clock and plant responses to biotic and abiotic stresses. The pleiotropic phenotypes of spy mutants point to the likely role of AtSPY in regulating key proteins functioning in diverse cellular pathways. However, very few AtSPY targets are known. Here, we identified 88 SPY targets from Arabidopsis (Arabidopsis thaliana) and Nicotiana benthamiana via the purification of O-fucosylated peptides using Aleuria aurantia lectin followed by electron transfer dissociation-MS/MS analysis. Most AtSPY targets were nuclear proteins that function in DNA repair, transcription, RNA splicing, and nucleocytoplasmic transport. Cytoplasmic AtSPY targets were involved in microtubule-mediated cell division/growth and protein folding. A comparison with the published O-linked-N-acetylglucosamine (O-GlcNAc) proteome revealed that 30% of AtSPY targets were also O-GlcNAcylated, indicating that these distinct glycosylations could co-regulate many protein functions. This study unveiled the roles of O-fucosylation in modulating many key nuclear and cytoplasmic proteins and provided a valuable resource for elucidating the regulatory mechanisms involved.

The CCCH-Type Zinc-Finger Protein GhC3H20 Enhances Salt Stress Tolerance in Arabidopsis thaliana and Cotton through ABA Signal Transduction Pathway

The CCCH zinc-finger protein contains a typical C3H-type motif widely existing in plants, and it plays an important role in plant growth, development, and stress responses. In this study, a CCCH zinc-finger gene, GhC3H20, was isolated and thoroughly characterized to regulate salt stress in cotton and Arabidopsis. The expression of GhC3H20 was up-regulated under salt, drought, and ABA treatments. GUS activity was detected in the root, stem, leaves, and flowers of ProGhC3H20::GUS transgenic Arabidopsis. Compared with the control, the GUS activity of ProGhC3H20::GUS transgenic Arabidopsis seedlings under NaCl treatment was stronger. Through the genetic transformation of Arabidopsis, three transgenic lines of 35S-GhC3H20 were obtained. Under NaCl and mannitol treatments, the roots of the transgenic lines were significantly longer than those of the wild-type (WT) Arabidopsis. The leaves of the WT turned yellow and wilted under high-concentration salt treatment at the seedling stage, while the leaves of the transgenic Arabidopsis lines did not. Further investigation showed that compared with the WT, the content of catalase (CAT) in the leaves of the transgenic lines was significantly higher. Therefore, compared with the WT, overexpression of GhC3H20 enhanced the salt stress tolerance of transgenic Arabidopsis. A virus-induced gene silencing (VIGS) experiment showed that compared with the control, the leaves of pYL156-GhC3H20 plants were wilted and dehydrated. The content of chlorophyll in pYL156-GhC3H20 leaves was significantly lower than those of the control. Therefore, silencing of GhC3H20 reduced salt stress tolerance in cotton. Two interacting proteins (GhPP2CA and GhHAB1) of GhC3H20 have been identified through a yeast two-hybrid assay. The expression levels of PP2CA and HAB1 in transgenic Arabidopsis were higher than those in the WT, and pYL156-GhC3H20 had expression levels lower than those in the control. GhPP2CA and GhHAB1 are the key genes involved in the ABA signaling pathway. Taken together, our findings demonstrate that GhC3H20 may interact with GhPP2CA and GhHAB1 to participate in the ABA signaling pathway to enhance salt stress tolerance in cotton.

Zinc-finger protein GmZF351 improves both salt and drought stress tolerance in soybean

Abiotic stress is one of the most important factors reducing soybean yield. It is essential to identify regulatory factors contributing to stress responses. A previous study found that the tandem CCCH zinc-finger protein GmZF351 is an oil level regulator. In this study, we discovered that the GmZF351 gene is induced by stress and that the overexpression of GmZF351 confers stress tolerance to transgenic soybean. GmZF351 directly regulates the expression of GmCIPK9 and GmSnRK, leading to stomata closing, by binding to their promoter regions, which carry two CT(G/C)(T/A)AA elements. Stress induction of GmZF351 is mediated through reduction in the H3K27me3 level at the GmZF351 locus. Two JMJ30-demethylase-like genes, GmJMJ30-1 and GmJMJ30-2, are involved in this demethylation process. Overexpression of GmJMJ30-1/2 in transgenic hairy roots enhances GmZF351 expression mediated by histone demethylation and confers stress tolerance to soybean. Yield-related agronomic traits were evaluated in stable GmZF351-transgenic plants under mild drought stress conditions. Our study reveals a new mode of GmJMJ30-GmZF351 action in stress tolerance, in addition to that of GmZF351 in oil accumulation. Manipulation of the components in this pathway is expected to improve soybean traits and adaptation under unfavorable environments.

Co-expression network of heat-response transcripts: A glimpse into how splicing factors impact rice basal thermotolerance

To identify novel solutions to improve rice yield under rising temperatures, molecular components of thermotolerance must be better understood. Alternative splicing (AS) is a major post-transcriptional mechanism impacting plant tolerance against stresses, including heat stress (HS). AS is largely regulated by splicing factors (SFs) and recent studies have shown their involvement in temperature response. However, little is known about the splicing networks between SFs and AS transcripts in the HS response. To expand this knowledge, we constructed a co-expression network based on a publicly available RNA-seq dataset that explored rice basal thermotolerance over a time-course. Our analyses suggest that the HS-dependent control of the abundance of specific transcripts coding for SFs might explain the widespread, coordinated, complex, and delicate AS regulation of critical genes during a plant's inherent response to extreme temperatures. AS changes in these critical genes might affect many aspects of plant biology, from organellar functions to cell death, providing relevant regulatory candidates for future functional studies of basal thermotolerance.

OsTZF1, a CCCH-tandem zinc finger protein gene, driven under own promoter produces no pleiotropic effects and confers salt and drought tolerance in rice

Different abiotic stresses induce OsTZF1, a tandem CCCH-type zinc finger domain gene, in rice. Here, we report that transgenic rice plants overexpressing OsTZF1 under own promoter (P_OsTZF1:OsTZF1-OX [for overexpression]) transferred to soil showed normal growth similar to vector control plants. The P_OsTZF1:OsTZF1-OX produced normal leaves without any lesion mimic phenotype and exhibited normal seed setting. The P_OsTZF1:OsTZF1-OX plants showed significantly increased tolerance to salt and drought stresses and enhanced post stress recovery. Microarray analysis revealed a total of 846 genes up-regulated and 360 genes down-regulated in P_OsTZF1:OsTZF1-OX salt-treated plants. Microarray analysis of P_OsTZF1:OsTZF1-OX plants showed the regulation of many abiotic stress tolerance genes. These results suggest that OsTZF1-OX under own promoter show abiotic stress tolerance and produces no pleiotropic effect on phenotype of transgenic rice plant.

Comparative Transcriptome Analysis of CCCH Family in Roles of Flower Opening and Abiotic Stress in Osmanthus fragrans

CCCH is a zinc finger family with a typical CCCH-type motif which performs a variety of roles in plant growth and development and responses to environmental stressors. However, the information about this family has not been reported for Osmanthus fragrans. In this study, a total of 66 CCCH predicted genes were identified from the O. fragrans genome, the majority of which had multiple CCCH motifs. The 66 OfCCCHs were found to be unevenly distributed on 21 chromosomes and were clustered into nine groups based on their phylogenetic analysis. In each group, the gene structure and domain makeup were comparatively conserved. The expression profiles of the OfCCCH genes were examined in various tissues, the flower-opening processes, and under various abiotic stresses using transcriptome sequencing and qRT-PCR (quantitative real-time PCR). The results demonstrated the widespread expression of OfCCCHs in various tissues, the differential expression of 22 OfCCCHs during flower-opening stages, and the identification of 4, 5, and 13 OfCCCHs after ABA, salt, and drought stress treatment, respectively. Furthermore, characterization of the representative OfCCCHs (OfCCCH8, 23, 27, and 36) revealed that they were all localized in the nucleus and that the majority of them had transcriptional activation in the yeast system. Our research offers the first thorough examination of the OfCCCH family and lays the groundwork for future investigations regarding the functions of CCCH genes in O. fragrans.

Hormone Regulation of CCCH Zinc Finger Proteins in Plants

CCCH zinc finger proteins contain one to six tandem CCCH motifs composed of three cysteine and one histidine residues and have been widely found in eukaryotes. Plant CCCH proteins control a wide range of developmental and adaptive processes through DNA-protein, RNA-protein and/or protein-protein interactions. The complex networks underlying these processes regulated by plant CCCH proteins are often involved in phytohormones as signal molecules. In this review, we described the evolution of CCCH proteins from green algae to vascular plants and summarized the functions of plant CCCH proteins that are influenced by six major hormones, including abscisic acid, gibberellic acid, brassinosteroid, jasmonate, ethylene and auxin. We further compared the regulatory mechanisms of plant and animal CCCH proteins via hormone signaling. Among them, Arabidopsis AtC3H14, 15 and human hTTP, three typical CCCH proteins, are able to integrate multiple hormones to participate in various biological processes.

A tandem CCCH type zinc finger protein gene CpC3H3 from Chimonanthus praecox promotes flowering and enhances drought tolerance in Arabidopsis

BACKGROUND

CCCH-type zinc finger proteins play important roles in plant development and biotic/abiotic stress responses. Wintersweet (Chimonanthus praecox) is a popular ornamental plant with strong resistance to various stresses, which is a good material for exploring gene resource for stress response. In this study, we isolated a CCCH type zinc finger protein gene CpC3H3 (MZ964860) from flower of wintersweet and performed functional analysis with a purpose of identifying gene resource for floral transition and stress tolerance.

RESULTS

CpC3H3 was predicted a CCCH type zinc finger protein gene encoding a protein containing 446 amino acids with five conserved C-X₈-C-X₅-C-X₃-H motifs. CpC3H3 was localized in the cell membrane but with a nuclear export signal at the N-terminal. Transcripts of CpC3H3 were significantly accumulated in flower buds at floral meristem formation stage, and were induced by polyethylene glycol. Overexpression of CpC3H3 promoted flowering, and enhanced drought tolerance in transgenic A. thaliana. CpC3H3 overexpression affects the expression level of genes involved in flower inducement and stress responses. Further comparative studies on physiological indices showed the contents of proline and soluble sugar, activity of peroxidase and the rates of electrolyte leakage were significantly increased and the content of malondialdehyde and osmotic potential was significantly reduced in transgenic A. thaliana under PEG stress.

CONCLUSION

Overall, CpC3H3 plays a role in flowering inducement and drought tolerance in transgenic A. thaliana. The CpC3H3 gene has the potential to be used to promote flowering and enhance drought tolerance in plants.

Genomic-environmental associations in wild cranberry (Vaccinium macrocarpon Ait.)

Understanding the genetic basis of local adaptation in natural plant populations, particularly crop wild relatives, may be highly useful for plant breeding. By characterizing genetic variation for adaptation to potentially stressful environmental conditions, breeders can make targeted use of crop wild relatives to develop cultivars for novel or changing environments. This is especially appealing for improving long-lived woody perennial crops such as the American cranberry (Vaccinium macrocarpon Ait.), the cultivation of which is challenged by biotic and abiotic stresses. In this study, we used environmental association analyses in a collection of 111 wild cranberry accessions to identify potentially adaptive genomic regions for a range of bioclimatic and soil conditions. We detected 126 significant associations between SNP marker loci and environmental variables describing temperature, precipitation, and soil attributes. Many of these markers tagged genes with functional annotations strongly suggesting a role in adaptation to biotic or abiotic conditions. Despite relatively low genetic variation in cranberry, our results suggest that local adaptation to divergent environments is indeed present, and the identification of potentially adaptive genetic variation may enable a selective use of this germplasm for breeding more stress-tolerant cultivars.

Genome-Wide Identification and Expression Analysis of the Zinc Finger Protein Gene Subfamilies under Drought Stress in Triticum aestivum

The zinc finger protein (ZFP) family is one of plants’ most diverse family of transcription factors. These proteins with finger-like structural domains have been shown to play a critical role in plant responses to abiotic stresses such as drought. This study aimed to systematically characterize Triticum aestivum ZFPs (TaZFPs) and understand their roles under drought stress. A total of 9 TaC2H2, 38 TaC3HC4, 79 TaCCCH, and 143 TaPHD were identified, which were divided into 4, 7, 12, and 14 distinct subgroups based on their phylogenetic relationships, respectively. Segmental duplication dominated the evolution of four subfamilies and made important contributions to the large-scale amplification of gene families. Syntenic relationships, gene duplications, and Ka/Ks result consistently indicate a potential strong purifying selection on TaZFPs. Additionally, TaZFPs have various abiotic stress-associated cis-acting regulatory elements and have tissue-specific expression patterns showing different responses to drought and heat stress. Therefore, these genes may play multiple functions in plant growth and stress resistance responses. This is the first comprehensive genome-wide analysis of ZFP gene families in T. aestivum to elucidate the basis of their function and resistance mechanisms, providing a reference for precise manipulation of genetic engineering for drought resistance in T. aestivum.

Genome-wide characterization and sequence polymorphism analyses of cysteine-rich poly comb-like protein in Glycine max

Cysteine-rich poly comb-like protein (CPP) is a member of cysteine-rich transcription factors that regulates plant growth and development. In the present work, we characterized twelve CPP transcription factors encoding genes in soybean (Glycine max). Phylogenetic analyses classified CPP genes into six clades. Sequence logos analyses between G. max and G. soja amino acid residues exhibited high conservation. The presence of growth and stress-related cis-acting elements in the upstream regions of GmCPPs highlight their role in plant development and tolerance against abiotic stress. Ka/Ks levels showed that GmCPPs experienced limited selection pressure with limited functional divergence arising from segmental or whole genome duplication events. By using the PAN-genome of soybean, a single nucleotide polymorphism was identified in GmCPP-6. To perform high throughput genotyping, a kompetitive allele-specific PCR (KASP) marker was developed. Association analyses indicated that GmCPP-6-T allele of GmCPP-6 (in exon region) was associated with higher thousand seed weight under both water regimes (well-water and water-limited). Taken together, these results provide vital information to further decipher the biological functions of CPP genes in soybean molecular breeding.

Transcriptome-Wide Identification of CCCH-Type Zinc Finger Proteins Family in Pinus massoniana and RR-TZF Proteins in Stress Response

CCCH-type zinc finger proteins play an important role in multiple biotic and abiotic stresses. More and more reports about CCCH functions in plant development and stress responses have appeared over the past few years, focusing especially on tandem CCCH zinc finger proteins (TZFs). However, this has not been reported in Pinaceae. In this study, we identified 46 CCCH proteins, including 6 plant TZF members in Pinus massoniana, and performed bioinformatic analysis. According to RT-PCR analysis, we revealed the expression patterns of five RR-TZF genes under different abiotic stresses and hormone treatments. Meanwhile, tissue-specific expression analysis suggested that all genes were mainly expressed in needles. Additionally, RR-TZF genes showed transcriptional activation activity in yeast. The results in this study will be beneficial in improving the stress resistance of P. massoniana and facilitating further studies on the biological and molecular functions of CCCH zinc finger proteins.

AaZFP3, a Novel CCCH-Type Zinc Finger Protein from Adonis amurensis, Promotes Early Flowering in Arabidopsis by Regulating the Expression of Flowering-Related Genes

CCCH-type zinc finger proteins (ZFP) are a large family of proteins that play various important roles in plant growth and development; however, the functions of most proteins in this family are uncharacterized. In this study, a CCCH-type ZFP, AaZFP3, was identified in the floral organ of Adonis amurensis. Quantitative real-time PCR (qPCR) analysis revealed that AaZFP3 was widely expressed in the flowers of A.amurensis. Subcellular localization analysis showed that the AaZFP3 protein was mainly localized to the cytoplasm in tobacco and Arabidopsis. Furthermore, the overexpression of AaZFP3 promoted early flowering in Arabidopsis under both normal and relatively low-temperature conditions. RNA-sequencing and qPCR analyses revealed that the expression of multiple key flowering-time genes was altered in transgenic Arabidopsis overexpressing AaZFP3 compared to wild-type. Of these genes, FLOWERING LOCUS T (AtFT) expression was most significantly up-regulated, whereas FLOWERING LOCUS C (AtFLC) was significantly down-regulated. These results suggest that the overexpression of AaZFP3 promotes early flowering in Arabidopsis by affecting the expression of flowering-time genes. Overall, our study indicates that AaZFP3 may be involved in flowering regulation in A.amurensis and may represent an important genetic resource for improving flowering-time control in other ornamental plants or crops.

Multifaceted roles of zinc finger proteins in regulating various agronomic traits in rice

Rice is an important cereal crop, which provides staple food for more than half of the world's population. To meet the demand of the ever-growing population in the next few decades, an extra increase in rice yield is an urgent need. Given that various agronomic traits contribute to the yield of rice, deciphering the key regulators involved in multiple agronomic trait formation is particularly important. As a superfamily of transcription factors, zinc finger proteins participate in regulating multiple genes in almost every stage of rice growth and development. Therefore, understanding zinc finger proteins underlying regulatory network would provide insights into the regulation of agronomic traits in rice. To this end, we intend to summarize the current advances in zinc finger proteins, with emphasis on C2H2 and CCCH proteins, and then discuss their potential in improving rice yield.

PagGRF11 Overexpression Promotes Stem Development and Dwarfing in Populus

Poplar is not only an important woody plant, but also a model species for molecular plant studies. We identified PagGRF11 (pAxG07Gg0005700), a homolog of the Arabidopsis AtGRF1 (AT4G37740) and AtGRF2 (AT2G22840) gene. We transformed the poplar clone "84K" with PagGRF11, and the transgenic overexpressed plants (PagGRF11-OE) showed plant height reduction (dwarfing), stem diameter increase, internode shortening, and larger leaf area. The Arabidopsis overexpression line grf-oe (Overexpression of PagGRF11 in Arabidopsis), mutant line atgrf (a loss-of-function mutant of the AtGRF1 gene of Arabidopsis thaliana), and mutant trans-complementary line atgrf+oe (overexpression of PagGRF11 in mutant plants (atgrf)) also showed different leaf size phenotypes. Further, tissue sections revealed that increased xylem production was the main cause of stem thickening. Transcriptome differential expression analysis of PagGRF11 overexpressed and control plants showed that PagGRF11 promoted CCCH39(C3H39) expression. The expression profile of CCCH39 in different tissues showed that it was highly expressed in xylem. Yeast single hybrid and instantaneous double luciferase assay results showed that PagGRF11 directly transcribed and activated CCCH39 expression through interaction with cis-acting element GARE (TCTGTTG), thus promoting xylem development. This is the first finding that GRF positively regulates xylem development through CCCH39 expression activation and further suggests that PagGRF11 is a potential target for increasing wood yield.

Highly Overexpressed AtC3H18 Impairs Microgametogenesis via Promoting the Continuous Assembly of mRNP Granules

Plant CCCH zinc-finger proteins form a large family of regulatory proteins function in many aspects of plant growth, development and environmental responses. Despite increasing reports indicate that many CCCH zinc-finger proteins exhibit similar subcellular localization of being localized in cytoplasmic foci, the underlying molecular mechanism and the connection between this specific localization pattern and protein functions remain largely elusive. Here, we identified another cytoplasmic foci-localized CCCH zinc-finger protein, AtC3H18, in Arabidopsis thaliana. AtC3H18 is predominantly expressed in developing pollen during microgametogenesis. Although atc3h18 mutants did not show any abnormal phenotype, possibly due to redundant gene(s), aberrant AtC3H18 expression levels caused by overexpression resulted in the assembly of AtC3H18-positive granules in a dose-dependent manner, which in turn led to male sterility phenotype, highlighting the importance of fine-tuned AtC3H18 expression. Further analyzes demonstrated that AtC3H18-positive granules are messenger ribonucleoprotein (mRNP) granules, since they can exhibit liquid-like physical properties, and are associated with another two mRNP granules known as processing bodies (PBs) and stress granules (SGs), reservoirs of translationally inhibited mRNAs. Moreover, the assembly of AtC3H18-positive granules depends on mRNA availability. Combined with our previous findings on the AtC3H18 homologous genes in Brassica campestris, we concluded that appropriate expression level of AtC3H18 during microgametogenesis is essential for normal pollen development, and we also speculated that AtC3H18 may act as a key component of mRNP granules to modulate pollen mRNAs by regulating the assembly/disassembly of mRNP granules, thereby affecting pollen development.

DiZF-C3H1, a zinc finger transcription factor from the dove tree (Davidia involucrata Baill.), plays a negative role in seed development and plant growth in Arabidopsis and tobacco

Low seed fertility seriously limits the survival and adaption of rare plant species. Here, we identified a seed-specific gene, DiZF-C3H1, from the dove tree and verified its function. Overexpression of DiZF-C3H1 caused retarded root development, delayed anthesis, abnormal floral organs, and deformed siliques in transgenic Arabidopsis lines. No offspring were obtained in transgenic Arabidopsis lines due to serious seed abortion. Therefore, we performed further verification in tobacco. Similarly, overexpression of DiZF-C3H1 retarded root development and reduced berry size and seed yield in transgenic tobacco lines. Moreover, although transgenic tobacco offspring were obtained, the viability of transgenic seeds was reduced and their germination was delayed. In addition, faded flowers were observed in transgenic tobacco lines. Taken together, DiZF-C3H1 was verified to play a negative role in root growth, floral organ development, and especially seed development in Arabidopsis and tobacco. This appears to be a deleterious gene for these model plants with high seed fertility. However, this function might be of special significance for Davidia, whose seed dormancy period is extremely long; DiZF-C3H1 might play a critical role in the distinctive reproduction strategy adopted by this rare and endangered species.

Genetic Mapping to Detect Stringent QTLs Using 1k-RiCA SNP Genotyping Platform from the New Landrace Associated with Salt Tolerance at the Seedling Stage in Rice

Rice is the world’s most important food crop, providing the daily calorie intake for more than half of the world’s population. Rice breeding has always been preoccupied with maximizing yield potential. However, numerous abiotic factors, such as salt, cold, drought, and heat, significantly reduce rice productivity. Salinity, one of the major abiotic stresses, reduces rice yield worldwide. This study was conducted to determine new quantitative trait loci (QTLs) that regulate salt tolerance in rice seedlings. One F_2:3 mapping population was derived from a cross between BRRI dhan49 (a popular but sensitive rainfed rice variety) and Akundi (a salt-tolerant rice landrace in Bangladesh used as a donor parent). The 1k-Rice Custom Amplicon (1k-RiCA) single-nucleotide polymorphism (SNP) markers were used to genotype this mapping population. After removing segregation distortion and monomorphic markers, 884 SNPs generated a 1526.8 cM-long genetic linkage map with a mean marker density of 1.7 cM for the 12 linkage groups. By exploiting QGene and ICIM-ADD, a sum of 15 QTLs for nine traits was identified in salt stress on seven chromosomes. Four important genomic loci were identified (qSES1, qSL1, qSUR1 and qRL1) on chromosome 1. Out of these 15 QTLs, 14 QTLs are unique, as no other study has mapped in the same chromosomal location. We also detected 15 putative candidate genes and their functions. The ICIM-EPI approach identified 43 significant pairwise epistasis interactions between regions associated with and unassociated with QTLs. Apart from more well-known donors, Akundi serves as an important new donor source for global salt tolerance breeding initiatives, including Bangladesh. The introgression of the novel QTLs identified in this study will accelerate the development of new salt-tolerant varieties that are highly resistant to salt stress using marker-enabled breeding.

DgbZIP3 interacts with DgbZIP2 to increase the expression of DgPOD for cold stress tolerance in chrysanthemum

The bZIP transcription factor plays a very important role in abiotic stresses, e.g. drought, salt, and low-temperature stress, but the mechanism of action at low temperature is still unclear. In this study, overexpression of DgbZIP3 led to increased tolerance of chrysanthemum (Chrysanthemum morifolium Ramat.) to cold stress, whereas antisense suppression of DgbZIP3 resulted in decreased tolerance. Electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP), luciferase complementary imaging analysis (LCI), and dual-luciferase reporter gene detection (DLA) experiments indicated that DgbZIP3 directly bound to the promoter of DgPOD and activated its expression. DgbZIP2 was identified as a DgbZIP3-interacting protein using yeast two-hybrid, co-immunoprecipitation, LCI, and bimolecular fluorescence complementation assays. Overexpression of DgbZIP2 led to increased tolerance of chrysanthemum to cold stress, whereas antisense suppression of DgbZIP2 resulted in decreased tolerance. A ChIP-qPCR experiment showed that DgbZIP2 was highly enriched in the promoter of DgPOD, while DLA, EMSA, and LCI experiments further showed that DgbZIP2 could not directly regulate the expression of DgPOD. The above results show that DgbZIP3 interacts with DgbZIP2 to regulate the expression of DgPOD to promote an increase in peroxidase activity, thereby regulating the balance of reactive oxygen species and improving the tolerance of chrysanthemum to low-temperature stress.

The CCCH zinc finger protein C3H15 negatively regulates cell elongation by inhibiting brassinosteroid signaling

Plant CCCH proteins participate in the control of multiple developmental and adaptive processes, but the regulatory mechanisms underlying these processes are not well known. In this study, we showed that the Arabidopsis (Arabidopsis thaliana) CCCH protein C3H15 negatively regulates cell elongation by inhibiting brassinosteroid (BR) signaling. Genetic and biochemical evidence showed that C3H15 functions downstream of the receptor BR INSENSITIVE 1 (BRI1) as a negative regulator in the BR pathway. C3H15 is phosphorylated by the GLYCOGEN SYNTHASE KINASE 3 -like kinase BR-INSENSITIVE 2 (BIN2) at Ser111 in the cytoplasm in the absence of BRs. Upon BR perception, C3H15 transcription is enhanced, and the phosphorylation of C3H15 by BIN2 is reduced. The dephosphorylated C3H15 protein accumulates in the nucleus, where C3H15 regulates transcription via G-rich elements (typically GGGAGA). C3H15 and BRASSINAZOLE RESISTANT 1 (BZR1)/BRI1-EMS-SUPPRESSOR 1 (BES1), two central transcriptional regulators of BR signaling, directly suppress each other and share a number of BR-responsive target genes. Moreover, C3H15 antagonizes BZR1 and BES1 to regulate the expression of their shared cell elongation-associated target gene, SMALL AUXIN-UP RNA 15 (SAUR15). This study demonstrates that C3H15-mediated BR signaling may be parallel to, or even attenuate, the dominant BZR1 and BES1 signaling pathways to control cell elongation. This finding expands our understanding of the regulatory mechanisms underlying BR-induced cell elongation in plants.

OsMAPK6 phosphorylates a zinc finger protein OsLIC to promote downstream OsWRKY30 for rice resistance to bacterial blight and leaf streak

Rice OsLIC encoding a CCCH zinc finger transcription factor plays an important role in immunity. However, the immune signaling pathways that OsLIC-involved and the underlying mechanisms that OsLIC-conferred resistance against pathogens are largely unclear. Here, we show that OsLIC, as a substrate for OsMAPK6, negatively regulates resistance to Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc) by directly suppressing OsWRKY30 transcription. Biochemical assays showed that OsLIC bound to OsWRKY30 promoter and suppressed its transcription. Genetic assays confirmed that the osilc knockout mutants and OsWRKY30-overexpressing plants exhibited enhanced resistance to Xoo and Xoc, knocking out OsWRKY30 in the oslic mutants attenuated the resistance against bacterial pathogens. OsMAPK6 physically interacted with and phosphorylated OsLIC leading to decreased OsLIC DNA-binding activity, therefore, overexpression of OsLIC partially suppressed OsMAPK6-mediated rice resistance. In addition, both OsMAPK6-phosphorylated activation of OsLIC and phosphorylation-mimic OsLIC^5D had reduced DNA-binding activity towards OsWRKY30 promoter, thereby promoting OsWRKY30 transcription. Collectively, these results reveal that OsMAPK6-mediated phosphorylation of OsLIC positively regulates rice resistance to Xoo and Xoc by modulating OsWRKY30 transcription, suggesting that OsMAPK6-OsLIC-OsWRKY30 module is an immune signaling pathway in response to the bacterial pathogens.

The role of post-transcriptional modulators of metalloproteins in response to metal deficiencies

Copper and iron proteins have a wide range of functions in living organisms. Metal assembly into metalloproteins is a complex process, where mismetalation is detrimental and energy consuming to cells. Under metal deficiency, metal distribution is expected to reach a metalation ranking, prioritizing essential versus dispensable metalloproteins, while avoiding interference with other metals and protecting metal-sensitive processes. In this review, we propose that post-transcriptional modulators of metalloprotein mRNA (ModMeR) are good candidates in metal prioritization under metal-limited conditions. ModMeR target high quota or redundant metalloproteins and, by adjusting their synthesis, ModMeR act as internal metal distribution valves. Inappropriate metalation of ModMeR targets could compete with metal delivery to essential metalloproteins and interfere with metal-sensitive processes, such as chloroplastic photosynthesis and mitochondrial respiration. Regulation of ModMeR targets could increase or decrease the metal flow through interconnected pathways in cellular metal distribution, helping to achieve adequate differential metal requirements. Here, we describe and compare ModMeR that function in response to copper and iron deficiencies. Specifically, we describe copper-miRNAs from Arabidopsis thaliana and diverse iron ModMeR from yeast, mammals, and bacteria under copper and iron deficiencies, as well as the influence of oxidative stress. Putative functions derived from their role as ModMeR are also discussed.

CCCH Zinc finger genes in Barley: genome-wide identification, evolution, expression and haplotype analysis

BACKGROUND

CCCH transcription factors are important zinc finger transcription factors involved in the response to biotic and abiotic stress and physiological and developmental processes. Barley (Hordeum vulgare) is an agriculturally important cereal crop with multiple uses, such as brewing production, animal feed, and human food. The identification and assessment of new functional genes are important for the molecular breeding of barley.

RESULTS

In this study, a total of 53 protein-encoding CCCH genes unevenly dispersed on seven different chromosomes were identified in barley. Phylogenetic analysis categorized the barley CCCH genes (HvC3Hs) into eleven subfamilies according to their distinct features, and this classification was supported by intron-exon structure and conserved motif analysis. Both segmental and tandem duplication contributed to the expansion of CCCH gene family in barley. Genetic variation of HvC3Hs was characterized using publicly available exome-capture sequencing datasets. Clear genetic divergence was observed between wild and landrace barley populations in HvC3H genes. For most HvC3Hs, nucleotide diversity and the number of haplotype polymorphisms decreased during barley domestication. Furthermore, the HvC3H genes displayed distinct expression profiles for different developmental processes and in response to various types of stresses. The HvC3H1, HvC3H2 and HvC3H13 of arginine-rich tandem CCCH zinc finger (RR-TZF) genes were significantly induced by multiple types of abiotic stress and/or phytohormone treatment, which might make them as excellent targets for the molecular breeding of barley.

CONCLUSIONS

Overall, our study provides a comprehensive characterization of barley CCCH transcription factors, their diversity, and their biological functions.

Genome-Wide Analysis and Characterization of the Proline-Rich Extensin-like Receptor Kinases (PERKs) Gene Family Reveals Their Role in Different Developmental Stages and Stress Conditions in Wheat (Triticum aestivum L.)

Proline-rich extensin-like receptor kinases (PERKs) are a class of receptor kinases implicated in multiple cellular processes in plants. However, there is a lack of information on the PERK gene family in wheat. Therefore, we identified 37 PERK genes in wheat to understand their role in various developmental processes and stress conditions. Phylogenetic analysis of PERK genes from Arabidopsis thaliana, Oryza sativa, Glycine max, and T. aestivum grouped them into eight well-defined classes. Furthermore, synteny analysis revealed 275 orthologous gene pairs in B. distachyon, Ae. tauschii, T. dicoccoides, O. sativa and A. thaliana. Ka/Ks values showed that most TaPERK genes, except TaPERK1, TaPERK2, TaPERK17, and TaPERK26, underwent strong purifying selection during evolutionary processes. Several cis-acting regulatory elements, essential for plant growth and development and the response to light, phytohormones, and diverse biotic and abiotic stresses, were predicted in the promoter regions of TaPERK genes. In addition, the expression profile of the TaPERK gene family revealed differential expression of TaPERK genes in various tissues and developmental stages. Furthermore, TaPERK gene expression was induced by various biotic and abiotic stresses. The RT-qPCR analysis also revealed similar results with slight variation. Therefore, this study's outcome provides valuable information for elucidating the precise functions of TaPERK in developmental processes and diverse stress conditions in wheat.

Non-TZF Transcriptional Activator AtC3H12 Negatively Affects Seed Germination and Seedling Development in Arabidopsis

CCCH zinc finger proteins are a large protein family and are classified as either tandem CCCH zinc finger (TZF) or non-TZF proteins. The roles of TZF genes in several plants have been well determined, whereas the functions of many non-TZF genes in plants remain uncharacterized. Herein, we describe biological and molecular functions of AtC3H12, an Arabidopsis non-TZF protein containing three CCCH zinc finger motifs. AtC3H12 has orthologs in several plant species but has no paralog in Arabidopsis. AtC3H12-overexpressing transgenic plants (OXs) germinated slower than wild-type (WT) plants, whereas atc3h12 mutants germinated faster than WT plants. The fresh weight (FW) and primary root lengths of AtC3H12 OX seedlings were lighter and shorter than those of WT seedlings, respectively. In contrast, FW and primary root lengths of atc3h12 seedlings were heavier and longer than those of WT seedlings, respectively. AtC3H12 was localized in the nucleus and displayed transactivation activity in both yeast and Arabidopsis. We found that the 97-197 aa region of AtC3H12 is an important part for its transactivation activity. Detection of expression levels and analysis of Arabidopsis transgenic plants harboring a PAtC3H12::GUS construct showed that AtC3H12 expression increases as the Arabidopsis seedlings develop. Taken together, our results demonstrate that AtC3H12 negatively affects seed germination and seedling development as a nuclear transcriptional activator in Arabidopsis. To our knowledge, this is the first report to show that non-TZF proteins negatively affect plant development as nuclear transcriptional activators.

Genome-wide identification and characterization of the CLASP_N gene family in upland cotton (Gossypium hirsutum L.)

BACKGROUND

Cytoplasmic linker-associated proteins (CLASPs) are tubule proteins that can bind to microtubules and participate in regulating the structure and function of microtubules, which significantly affects the development and growth of plants. These proteins have been identified in Arabidopsis; however, little research has been performed in upland cotton.

METHODS

In this study, the whole genome of the CLASP_N family was analyzed to provide theoretical support for the function of this gene family in the development of upland cotton fiber. Bioinformatics was used to analyze the family characteristics of CLASP_N in upland cotton, such as member identification, sequence characteristics, conserved domain structure and coevolutionary relationships. Real-time fluorescent quantitative PCR (qRT-PCR) was used to clarify the expression pattern of the upland cotton CLASP_N gene family in cotton fiber.

RESULTS

At the genome-wide level, we identified 16 upland cotton CLASP_N genes. A chromosomal localization analysis revealed that these 16 genes were located on 13 chromosomes. The motif results showed that all CLASP_N proteins have the CLASP_N domain. Gene structure analysis showed that the structure and length of exons and introns were consistent in the subgroups. In the evolutionary analysis with other species, the gene family clearly diverged from the other species in the evolutionary process. A promoter sequence analysis showed that this gene family contains a large number of cis-acting elements related to a variety of plant hormones. qRT-PCR was used to clarify the expression pattern of the upland cotton CLASP_N gene family in cotton fiber and leaves, and Gh210800 was found to be highly expressed in the later stages of fiber development. The results of this study provide a foundation for further research on the molecular role of the CLASP_N genes in cotton fiber development.

RNA Binding Protein OsTZF7 Traffics Between the Nucleus and Processing Bodies/Stress Granules and Positively Regulates Drought Stress in Rice

Tandem CCCH zinc finger (TZF) proteins are the essential components of processing bodies (PBs) and stress granules (SGs), which play critical roles in growth development and stress response in both animals and plants through posttranscriptional regulation of target mRNA. In this study, we characterized the biological and molecular functions of a novel tandem zinc finger protein, OsTZF7. The expression of OsTZF7 was upregulated by abiotic stresses, including polyethylene glycol (PEG) 4000, NaCl, and abscisic acid (ABA) in rice. Accordingly, the overexpression of OsTZF7 increased drought tolerance and enhanced sensitivity to exogenous ABA in rice, whereas the knockdown of OsTZF7 resulted in the opposite phenotype. RNA-seq analysis revealed that genes related to "response to stress," "abscisic acid signaling," "methylated histone binding," and "cytoplasmic mRNA processing body" are regulated by OsTZF7. We demonstrated that OsTZF7 can traffic between the nucleus and PBs/SGs, and the leucine-rich nuclear export signal (NES) mediates the nuclear export of OsTZF7. Additionally, we revealed that OsTZF7 can bind adenine- and uridine-rich (AU-rich) element (ARE) or ARE-like motifs within the 3' untranslated region of downregulated mRNAs, and interact with PWWP family proteins in vitro. Together, these results indicate that OsTZF7 positively regulates drought response in rice via ABA signaling and may be involved in mRNA turnover.

PuC3H35 confers drought tolerance by enhancing lignin and proanthocyanidin biosynthesis in the roots of Populus ussuriensis

Since the roots are the very organ where plants first sense and respond drought stress, it is of great importance to better understand root responses to drought. Yet the underlying molecular mechanisms governing root responses to drought stress have been poorly understood. Here, we identified and functionally characterized a CCCH type transcription factor, PuC3H35, and its targets, anthocyanin reductase (PuANR) and early Arabidopsis aluminum induced1 (PuEARLI1), which are involved in mediating proanthocyanidin (PA) and lignin biosynthesis in response to drought stress in Populus ussuriensis root. PuC3H35 was root-specifically induced upon drought stress. Overexpressing PuC3H35 promoted PA and lignin biosynthesis and vascular tissue development, resulting in enhanced tolerance to drought stress by the means of anti-oxidation and mechanical supporting. We further demonstrated that PuC3H35 directly bound to the promoters of PuANR and PuEARLI1 and overexpressing PuANR or PuEARLI1 increased root PA or lignin levels, respectively, under drought stress. Taken together, these results revealed a novel regulatory pathway for drought tolerance, in which PuC3H35 mediated PA and lignin biosynthesis by collaboratively regulating 'PuC3H35-PuANR-PA' and 'PuC3H35-PuEARLI1-PuCCRs-lignin' modules in poplar roots.

Identification and expression analysis of candidate genes related to seed dormancy and germination in the wheat GATA family

GATA transcription factors have been reported to function in plant growth and development and during various biotic/abiotic stresses in Arabidopsis and rice. However, the functions of wheat GATAs, particularly in the regulation of seed dormancy and germination, remain unclear. Here, we identified 78 TaGATAs in wheat and divided them into five subfamilies. Sixty-four paralogous pairs and 52 orthologous pairs were obtained, and Ka/Ks ratios showed that the TaGATAs had undergone strong purifying election during the evolutionary process. Triplet analysis indicated that a high homologue retention rate could explain the large number of TaGATAs in wheat. Gene structure analysis revealed that most members of the same subfamily had similar structures, and subcellular localization prediction indicated that most TaGATAs were located in the nucleus. Gene ontology annotation results showed that most TaGATAs had molecular functions in DNA and zinc binding, and promoter analysis suggested that they may play important roles in growth, development, and biotic/abiotic stress response. We combined three microarray datasets with qRT-PCR expression data from wheat varieties of contrasting dormancy and pre-harvest sprouting resistance levels during imbibition in order to identify ten candidate genes (TaGATA17/-25/-34/-37/-40/-46/-48/-51/-72/-73) that may be involved in the regulation of seed dormancy and germination in wheat. These findings provide valuable information for further dissection of TaGATA functions in the regulation of seed dormancy and germination, thereby enabling the improvement of wheat pre-harvest sprouting resistance by gene pyramiding.

Systematic analysis of CCCH zinc finger family in Brassica napus showed that BnRR-TZFs are involved in stress resistance

BACKGROUND

CCCH zinc finger family is one of the largest transcription factor families related to multiple biotic and abiotic stresses. Brassica napus L., an allotetraploid oilseed crop formed by natural hybridization between two diploid progenitors, Brassica rapa and Brassica oleracea. A systematic identification of rapeseed CCCH family genes is missing and their functional characterization is still in infancy.

RESULTS

In this study, 155 CCCH genes, 81 from its parent B. rapa and 74 from B. oleracea, were identified and divided into 15 subfamilies in B. napus. Organization and syntenic analysis explained the distribution and collinearity relationship of CCCH genes, the selection pressure and evolution of duplication gene pairs in B. napus genome. 44 diploid duplication gene pairs and 4 triple duplication gene groups were found in B. napus of CCCH family and the segmental duplication is attributed to most CCCH gene duplication events in B. napus. Nine types of CCCH motifs exist in B. napus CCCH family members, and motif C-X_7/8-C-X₅-C-X₃-H is the most common and a new conserved CCH motif (C-X₅-C-X₃-H) has been identified. In addition, abundant stress-related cis-elements exist in promoters of 27 subfamily IX (RR-TZF) genes and their expression profiles indicated that RR-TZF genes could be involved in responses to hormone and abiotic stress.

CONCLUSIONS

The results provided a foundation to understand the basic characterization and genes evolution of CCCH gene family in B. napus, and provided potential targets for genetic engineering in Brassicaceae crops in pursuit of stress-tolerant traits.

Transformation and Overexpression of Primary Cell Wall Synthesis-Related Zinc Finger Gene Gh_A07G1537 to Improve Fiber Length in Cotton

Molecular interventions have helped to explore the genes involved in fiber length, fiber strength, and other quality parameters with improved characteristics, particularly in cotton. The current study is an extension and functional validation of previous findings that Gh_A07G1537 influences fiber length in cotton using a chromosomal segment substitution line MBI7747 through RNA-seq data. The recombinant Gh_A07G1537 derived from the MBI7747 line was over-expressed in CCRI24, a genotype with a low profile of fiber quality parameters. Putative transformants were selected on MS medium containing hygromycin (25mg/ml), acclimatized, and shifted to a greenhouse for further growth and proliferation. Transgene integration was validated through PCR and Southern Blot analysis. Stable integration of the transgene (ΔGh_A07G1537) was validated by tracking its expression in different generations (T₀, T₁, and T₂) of transformed cotton plants. It was found to be 2.97-, 2.86-, and 2.92-folds higher expression in T₀, T₁, and T₂ plants, respectively, of transgenic compared with non-transgenic cotton plants. Fiber quality parameters were also observed to be improved in the engineered cotton line. Genetic modifications of Gh_A07G1537 support the improvement in fiber quality parameters and should be appreciated for the textile industry.

Reading between the Lines: RNA-seq Data Mining Reveals the Alternative Message of the Rice Leaf Transcriptome in Response to Heat Stress

Rice (Oryza sativa L.) is a major food crop but heat stress affects its yield and grain quality. To identify mechanistic solutions to improve rice yield under rising temperatures, molecular responses of thermotolerance must be understood. Transcriptional and post-transcriptional controls are involved in a wide range of plant environmental responses. Alternative splicing (AS), in particular, is a widespread mechanism impacting the stress defence in plants but it has been completely overlooked in rice genome-wide heat stress studies. In this context, we carried out a robust data mining of publicly available RNA-seq datasets to investigate the extension of heat-induced AS in rice leaves. For this, datasets of interest were subjected to filtering and quality control, followed by accurate transcript-specific quantifications. Powerful differential gene expression (DE) and differential AS (DAS) identified 17,143 and 2162 heat response genes, respectively, many of which are novel. Detailed analysis of DAS genes coding for key regulators of gene expression suggests that AS helps shape transcriptome and proteome diversity in response to heat. The knowledge resulting from this study confirmed a widespread transcriptional and post-transcriptional response to heat stress in plants, and it provided novel candidates for rapidly advancing rice breeding in response to climate change.

The transcription factor CmLEC1 positively regulates the seed-setting rate in hybridization breeding of chrysanthemum

Distant hybridization is widely used to develop crop cultivars, whereas the hybridization process of embryo abortion often severely reduces the sought-after breeding effect. The LEAFY COTYLEDON1 (LEC1) gene has been extensively investigated as a central regulator of seed development, but it is far less studied in crop hybridization breeding. Here we investigated the function and regulation mechanism of CmLEC1 from Chrysanthemum morifolium during its seed development in chrysanthemum hybridization. CmLEC1 encodes a nucleic protein and is specifically expressed in embryos. CmLEC1's overexpression significantly promoted the seed-setting rate of the cross, while the rate was significantly decreased in the amiR-CmLEC1 transgenic chrysanthemum. The RNA-Seq analysis of the developing hybrid embryos revealed that regulatory genes involved in seed development, namely, CmLEA (late embryogenesis abundant protein), CmOLE (oleosin), CmSSP (seed storage protein), and CmEM (embryonic protein), were upregulated in the OE (overexpressing) lines but downregulated in the amiR lines vs. wild-type lines. Future analysis demonstrated that CmLEC1 directly activated CmLEA expression and interacted with CmC3H, and this CmLEC1-CmC3H interaction could enhance the transactivation ability of CmLEC1 for the expression of CmLEA. Further, CmLEC1 was able to induce several other key genes related to embryo development. Taken together, our results show that CmLEC1 plays a positive role in the hybrid embryo development of chrysanthemum plants, which might involve activating CmLEA's expression and interacting with CmC3H. This may be a new pathway in the LEC1 regulatory network to promote seed development, one perhaps leading to a novel strategy to not only overcome embryo abortion during crop breeding but also increase the seed yield.

The Roles of CCCH Zinc-Finger Proteins in Plant Abiotic Stress Tolerance

Zinc-finger proteins, a superfamily of proteins with a typical structural domain that coordinates a zinc ion and binds nucleic acids, participate in the regulation of growth, development, and stress adaptation in plants. Most zinc fingers are C2H2-type or CCCC-type, named after the configuration of cysteine (C) and histidine (H); the less-common CCCH zinc-finger proteins are important in the regulation of plant stress responses. In this review, we introduce the domain structures, classification, and subcellular localization of CCCH zinc-finger proteins in plants and discuss their functions in transcriptional and post-transcriptional regulation via interactions with DNA, RNA, and other proteins. We describe the functions of CCCH zinc-finger proteins in plant development and tolerance to abiotic stresses such as salt, drought, flooding, cold temperatures and oxidative stress. Finally, we summarize the signal transduction pathways and regulatory networks of CCCH zinc-finger proteins in their responses to abiotic stress. CCCH zinc-finger proteins regulate the adaptation of plants to abiotic stress in various ways, but the specific molecular mechanisms need to be further explored, along with other mechanisms such as cytoplasm-to-nucleus shuttling and post-transcriptional regulation. Unraveling the molecular mechanisms by which CCCH zinc-finger proteins improve stress tolerance will facilitate the breeding and genetic engineering of crops with improved traits.

Evolutionary and Characteristic Analysis of RING-DUF1117 E3 Ubiquitin Ligase Genes in Gossypium Discerning the Role of GhRDUF4D in Verticillium dahliae Resistance

Verticillium wilt, primarily induced by the soil-borne fungus Verticillium dahliae, is a serious threat to cotton fiber production. There are a large number of really interesting new gene (RING) domain-containing E3 ubiquitin ligases in Arabidopsis, of which three (At2g39720 (AtRHC2A), At3g46620 (AtRDUF1), and At5g59550 (AtRDUF2)) have a domain of unknown function (DUF) 1117 domain in their C-terminal regions. This study aimed to detect and characterize the RDUF members in cotton, to gain an insight into their roles in cotton’s adaptation to environmental stressors. In this study, a total of 6, 7, 14, and 14 RDUF (RING-DUF1117) genes were detected in Gossypium arboretum, G. raimondii, G. hirsutum, and G. barbadense, respectively. These RDUF genes were classified into three groups. The genes in each group were highly conserved based on gene structure and domain analysis. Gene duplication analysis revealed that segmental duplication occurred during cotton evolution. Expression analysis revealed that the GhRDUF genes were widely expressed during cotton growth and under abiotic stresses. Many cis-elements related to hormone response and environment stressors were identified in GhRDUF promoters. The predicted target miRNAs and transcription factors implied that GhRDUFs might be regulated by gra-miR482c, as well as by transcription factors, including MYB, C2H2, and Dof. The GhRDUF genes responded to cold, drought, and salt stress and were sensitive to jasmonic acid, salicylic acid, and ethylene signals. Meanwhile, GhRDUF4D expression levels were enhanced after V. dahliae infection. Subsequently, GhRDUF4D was verified by overexpression in Arabidopsis and virus-induced gene silencing treatment in upland cotton. We observed that V. dahliae resistance was significantly enhanced in transgenic Arabidopsis, and weakened in GhRDUF4D silenced plants. This study conducted a comprehensive analysis of the RDUF genes in Gossypium, hereby providing basic information for further functional studies.

The CCCH zinc finger family of soybean (Glycine max L.): genome-wide identification, expression, domestication, GWAS and haplotype analysis

BACKGROUND

The CCCH zinc finger (zf_CCCH) is a unique subfamily featured one or more zinc finger motif(s) comprising of three Cys and one His residues. The zf_CCCH family have been reported involving in various processes of plant development and adaptation.

RESULTS

In this study, the zf_CCCH genes were identified via a genome-wide search and were systematically analyzed. 116 Gmzf_CCCHs were obtained and classified into seventeen subfamilies. Gene duplication and expansion analysis showed that tandem and segmental duplications contributed to the expansion of the Gmzf_CCCH gene family, and that segmental duplication play the main role. The expression patterns of Gmzf_CCCH genes were tissue-specific. Eleven domesticated genes were detected involved in the regulation of seed oil and protein synthesis as well as growth and development of soybean through GWAS and haplotype analysis for Gmzf_CCCH genes among the 164 of 302 soybeans resequencing data. Among which, 8 genes play an important role in the synthesis of seed oil or fatty acid, and the frequency of their elite haplotypes changes significantly among wild, landrace and improved cultivars, indicating that they have been strongly selected in the process of soybean domestication.

CONCLUSIONS

This study provides a scientific foundation for the comprehensive understanding, future cloning and functional studies of Gmzf_CCCH genes in soybean, meanwhile, it was also helpful for the improvement of soybean with high oil content.

Tristetraprolin: A cytosolic regulator of mRNA turnover moonlighting as transcriptional corepressor of gene expression

Tristetraprolin (TTP) is a nucleocytoplasmic 326 amino acid protein whose sequence is characterized by possessing two CCCH-type zinc finger domains. In the cytoplasm TTP function is to promote the degradation of mRNAs that contain adenylate/uridylate-rich elements (AREs). Mechanistically, TTP promotes the recruitment of poly(A)-specific deadenylases and exoribonucleases. By reducing the half-life of about 10% of all the transcripts in the cell TTP has been shown to participate in multiple cell processes that include regulation of gene expression, cell proliferation, metabolic homeostasis and control of inflammation and immune responses. However, beyond its role in mRNA decay, in the cell nucleus TTP acts as a transcriptional coregulator by interacting with chromatin modifying enzymes. TTP has been shown to repress the transactivation of NF-κB and estrogen receptor suggesting the possibility that it participates in the transcriptional regulation of hundreds of genes in human cells and its possible involvement in breast cancer progression. In this review, we discuss the cytoplasmic and nuclear functions of TTP and the effect of the dysregulation of its protein levels in the development of human diseases. We suggest that TTP be classified as a moonlighting tumor supressor protein that regulates gene expression through two different mechanims; the decay of ARE-mRNAs and a transcriptional coregulatory function.