Plant Hormone Signaling Pathways Research Articles

Progress in rice sheath blight resistance research.

Rice sheath blight (ShB) disease poses a major threat to rice yield throughout the world. However, the defense mechanisms against ShB in rice remain largely unknown. ShB resistance is a typical quantitative trait controlled by multiple genes. With the rapid development of molecular methods, many quantitative trait loci (QTLs) related to agronomic traits, biotic and abiotic stresses, and yield have been identified by genome-wide association studies. The interactions between plants and pathogens are controlled by various plant hormone signaling pathways, and the pathways synergistically or antagonistically interact with each other, regulating plant growth and development as well as the defense response. This review summarizes the regulatory effects of hormones including auxin, ethylene, salicylic acid, jasmonic acid, brassinosteroids, gibberellin, abscisic acid, strigolactone, and cytokinin on ShB and the crosstalk between the various hormones. Furthermore, the effects of sugar and nitrogen on rice ShB resistance, as well as information on genes related to ShB resistance in rice and their effects on ShB are also discussed. In summary, this review is a comprehensive description of the QTLs, hormones, nutrition, and other defense-related genes related to ShB in rice. The prospects of targeting the resistance mechanism as a strategy for controlling ShB in rice are also discussed.

Transcriptome Reveals the Molecular Mechanism of the ScALDH21 Gene from the Desert Moss Syntrichia caninervis Conferring Resistance to Salt Stress in Cotton.

The desert moss Syntrichia caninervis has proven to be an excellent plant material for mining resistance genes. The aldehyde dehydrogenase 21 (ScALDH21) gene from S. caninervis has been shown to confer tolerance to salt and drought, but it is unclear how the transgene ScALDH21 regulates tolerance to abiotic stresses in cotton. In the present work, we studied the physiological and transcriptome analyses of non-transgenic (NT) and transgenic ScALDH21 cotton (L96) at 0 day, 2 days, and 5 days after salt stress. Through intergroup comparisons and a weighted correlation network analysis (WGCNA), we found that there were significant differences between NT and L96 cotton in the plant hormone, Ca2+, and mitogen-activated protein kinase (MAPK) signaling pathways as well as for photosynthesis and carbohydrate metabolism. Overexpression of ScALDH21 significantly increased the expression of stress-related genes in L96 compared to NT cotton under both normal growth and salt stress conditions. These data suggest that the ScALDH21 transgene can scavenge more reactive oxygen species (ROS) in vivo relative to NT cotton and improve cotton resistance to salt stress by increasing the expression of stress-responsive genes, responding quickly to stress stimuli, enhancing photosynthesis and improving carbohydrate metabolism. Therefore, ScALDH21 is a promising candidate gene to improve resistance to salt stress, and the application of this gene in cotton provides new insights into molecular plant breeding.

Starch and Sucrose Metabolism and Plant Hormone Signaling Pathways Play Crucial Roles in Aquilegia Salt Stress Adaption.

Salt stress is one of the main abiotic stresses that strongly affects plant growth. Clarifying the molecular regulatory mechanism in ornamental plants under salt stress is of great significance for the ecological development of saline soil areas. Aquilegia vulgaris is a perennial with a high ornamental and commercial value. To narrow down the key responsive pathways and regulatory genes, we analyzed the transcriptome of A. vulgaris under a 200 mM NaCl treatment. A total of 5600 differentially expressed genes were identified. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis pointed out that starch and sucrose metabolism and plant hormone signal transduction were significantly improved. The above pathways played crucial roles when A. vulgaris was coping with salt stress, and their protein-protein interactions (PPIs) were predicted. This research provides new insights into the molecular regulatory mechanism, which could be the theoretical basis for screening candidate genes in Aquilegia.

Comparative transcriptome analysis of Saposhnikovia divaricata to reveal drought and rehydration adaption strategies.

Water scarcity has become one of the most prevalent environmental factors adversely affecting plant growth and development. Different species have developed multiple ways of drought resistance. Saposhnikovia divaricata is a commonly used traditional herb in East Asia. However, limited information is available on the drought response of this herb and further clarification of underlying molecular mechanism remains a challenge. In this study, a comparative transcriptome analysis was firstly conducted to identify the major pathways and candidate genes involved in the drought adaptive response of S. divaricata. The seedlings of S. divaricata were subjected to progressive drought by withholding water for 16 days followed by 8 days of rehydration. Transcriptome analysis identified a total of 89,784 annotated unigenes. The number of differentially expressed genes (DEGs) gradually increased with the deepening of drought and decreased after rehydration. Gene Ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis suggested genes related to oxidoreductase activity, carbohydrate metabolism, plant hormone signaling pathway and secondary metabolism were important in drought response of S. divaricata. Specific genes involved in reactive oxygen species scavenging system (POD, Cu/Zn-SOD, APX), abscisic acid and jasmonic acid signaling pathway (PYL4, PP2Cs, JAR1, JAZ) and phenylpropanoid biosynthesis (4CL, CCR, CAD) underwent dynamic alterations under drought and rehydration. Finally, the expression pattern of 12 selected DEGs from the transcriptomic profiling was validated by real-time quantitative PCR. Our study laid a foundation for understanding the stress response of S. divaricata and other Apiaceae family plant at molecular level.

A volatile producing Bacillus subtilis strain from the rhizosphere of Haloxylon ammodendron promotes plant root development

AimsThe colonization of plant growth-promoting rhizobacteria (PGPR) along plant roots in turn facilitates their ability to promote plant growth and health. In this study, we found that Bacillus subtilis strain WM13-24 from the rhizosphere of Haloxylon ammodendron was able to promote the growth of both Arabidopsis and its host plant. Furthermore, we found that volatile organic compounds (VOCs) from strain WM13-24 could promote plant growth by stimulating lateral root formation and root hair growth. However, the molecular mechanism underlying WM13-24-stimulated root development is still unknown.MethodsIn this study, a series of Arabidopsis mutants defective in specific plant hormone signaling pathways were used as materials to preliminarily study the effect of VOCs released by strain WM13-24 on plant root development through genetic and pharmacological methods. The volatile compounds of strain WM13-24 were identified by solid-phase microextraction gas chromatography-mass spectrometry (SPME–GC–MS).ResultsWM13-24 was able to promote the growth of both Arabidopsis and its host plant, H. ammodendron. Auxin signaling and transport played a crucial role in WM13-24-stimulated changes of root architectures in Arabidopsis. SPME–GC–MS analysis revealed that WM13-24 produces various classes of compounds. We further showed that 2,3-butanediol and benzyl alcohol were active in promoting plant growth and the growth responses of plants to the two VOCs were concentration dependent.ConclusionsAll these results suggested that VOCs emitted from B. subtilis strain WM13-24 from the rhizosphere of H. ammodendron improves root development depending on auxin signaling.

Comparative Transcriptome Analysis of Tolerant and Sensitive Genotypes of Common Bean (Phaseolus vulgaris L.) in Response to Terminal Drought Stress

We conducted a genome-wide transcriptomic analysis of three drought tolerant and sensitive genotypes of common bean to examine their transcriptional responses to terminal drought stress. We then conducted pairwise comparisons between the root and leaf transcriptomes from the resulting tissue based on combined transcriptomic data from the tolerant and sensitive genotypes. Our transcriptomic data revealed that 491 (6.4%) DEGs (differentially expressed genes) were upregulated in tolerant genotypes, whereas they were downregulated in sensitive genotypes; likewise, 396 (5.1%) DEGs upregulated in sensitive genotypes were downregulated in tolerant genotypes. Several transcription factors, heat shock proteins, and chaperones were identified in the study. Several DEGs in drought DB (data Base) overlapped between genotypes. The GO (gene ontology) terms for biological processes showed upregulation of DEGs in tolerant genotypes for sulfate and drug transmembrane transport when compared to sensitive genotypes. A GO term for cellular components enriched with upregulated DEGs for the apoplast in tolerant genotypes. These results substantiated the temporal pattern of root growth (elongation and initiation of root growth), and ABA-mediated drought response in tolerant genotypes. KEGG (kyoto encyclopedia of genes and genomes) analysis revealed an upregulation of MAPK (mitogen activated protein kinase) signaling pathways and plant hormone signaling pathways in tolerant genotypes. As a result of this study, it will be possible to uncover the molecular mechanisms of drought tolerance in response to terminal drought stress in the field. Further, genome-wide transcriptomic analysis of both tolerant and sensitive genotypes will assist us in identifying potential genes that may contribute to improving drought tolerance in the common bean.

Aged sweet corn (Zea mays L. saccharata Sturt) seeds trigger hormone and defense signaling during germination

Abstract: Seed ageing during storage or shipping can affect the yield and cost of agricultural production. Sweet corn is a naturally mutated corn cultivar with weak seed vitality during storage. In this study, we have shown that endogenous hormone level dynamics of fresh and aged sweet corn seeds were different during early geminating process. Transcriptomic assembling uncovered several novel transcripts during early stage of sweet corn germination in signal transduction and RNA processing pathways. Comparative transcriptomic profiling revealed that expression of many genes was activated earlier in aged seeds than fresh ones. Functional analyses showed that, as two major networks, plant hormone signaling and defense pathways were different between fresh and aged sweet corn seeds. Auxin, cytokinin, gibberellin, salicylic acid and jasmonic acid signaling pathways were activated earlier in aged seeds than fresh ones on the first day after imbibition. These results provided knowledge for understanding the ageing process of sweet corn seeds and several candidate genes for genetic study of seed ageing mechanism.

Metabolites from Bacillus subtilis J-15 Affect Seedling Growth of Arabidopsis thaliana and Cotton Plants.

Bacillus subtilis J-15 is a plant growth-promoting rhizobacteria isolated from the soil rhizosphere of cotton and is resistant to cotton verticillium wilt. This study evaluated the effects of metabolites of J-15 (J-15-Ms), including mycosubtilin, on plant growth using Arabidopsis and cotton plants. The results showed that J-15-Ms promoted Arabidopsis seeding growth at lower concentrations of 0.2 μg/mL but inhibited the growth at higher concentrations, such as 20 μg/mL. Similar results were obtained in cotton. Thus, J-15-Ms-treated plants showed low-concentration-induced growth promotion and high-concentration-induced growth inhibition. The J-15-Ms components were analyzed by liquid chromatography-mass spectrometry. Correlation analysis using the J-15 genomic databases suggested that J-15 may synthesize indoleacetic acid via the indole-3-pymvate pathway and indole-3-acetamide pathway. Treatment with mycosubtilin, a purified peptide from J-15-Ms, showed that the peptide promoted Arabidopsis growth at a low concentration (0.1 μg/mL) and inhibited plant growth at high concentrations (higher than 1 μg/mL), which also significantly increased plant lateral root number. Transcriptomic analysis showed that mycosubtilin might promote lateral root development and inhibit plant primary root growth by regulating the expression of the plant hormone signaling pathway. This study reveals the mechanism of Bacillus subtilis J-15 in affecting plant growth.

Photosynthesis, Phytohormone Signaling and Sugar Catabolism in the Culm Sheaths of Phyllostachys edulis.

Culm sheaths play an important role in supporting and protecting bamboo shoots during the growth and development period. The physiological and molecular functions of bamboo sheaths during the growth of bamboo shoots remain unclear. In this study, we investigated the morphological anatomy of culm sheaths, photosynthesis in sheath blades, storage and distribution of sugars, and the transcriptome of the sheath. Respiration in the base of the culm sheath was higher than that in the sheath blades; chloroplasts matured with the development of the sheath blades, the fluorescence efficiency Fv/Fm value increased from 0.3 to 0.82; and sucrose and hexose accumulated in the sheath blade and the culm sheath. The sucrose, glucose, and fructose contents of the middle sheath blades were 10.66, 5.73, and 8.84 mg/g FW, respectively. Starches accumulated in parenchymal cells close to vascular bundles. Genes related to the plant hormone signaling pathway and sugar catabolism were highly expressed in the culm sheath base. These findings provide a research basis for further understanding the possible role of bamboo sheaths in the growth and development of bamboo shoots.

Transcriptome characteristics during cell wall formation of endosperm cellularization and embryo differentiation in Arabidopsis.

Embryonic and endosperm development are important biological events during Arabidopsis seed development, and are controlled by dynamic changes in a range of gene expression. Nevertheless, the regulatory mechanisms of endosperm cellularization and embryo differentiation remain unclear. Here, we characterized the early embryo and endosperm development of the naa15 mutant that had abnormal embryo differentiation and incomplete endosperm cellularization compared to WT of Arabidopsis, and comparatively investigated the changes of gene expressions in WT seeds at 3, 4, and 5 days after pollination (3W, 4W, and 5W) and the white homozygous aborted naa15 seeds at 5, 6, and 7 DAP (5M, 6M, and 7M) from naa15-1/+ siliques using RNA sequencing and qPCR assays. The transcriptome analyses showed that there were 2040 and 3630 differentially expressed genes (DEGs) in 4W (at endosperm cellularization initiation stage and heart embryo stage) vs 3W (at syncytium stage and globular embryo stage), and 5W (at end of endosperm cellularization stage and torpedo embryo stage) vs 4W, respectively. The KEGG and GO analyses showed that lipid metabolic processes and transmembrane transport related to cell wall biogenesis, cell division and differentiation, the plant hormone signaling pathway, photosynthesis, and transcription regulator activity were evidently enriched in WT and naa15. The heatmap and qPCR analyses showed that auxin response genes (ARFs), auxin transport genes (PINs) cytokinin synthesis genes (LOGs), cytokinin dehydrogenase genes (CKXs), cytokinin receptor, transcription factors (MYB, bHLH, MADS-box, and ERF) were significantly downregulated in naa15 compared to WT. A series of cell wall genes annotated to xyloglucan endotransglycosylase/hydrolase, pectin methyl esterase, and pectin methyl esterase inhibitor were also identified in these DEGs. Moreover, using an immunofluorescent assay, the features of cell walls displayed that cellulose fluorescence signals in the embryo and endosperm of naa15 were significantly decreased, and the signals of low- and high- methyl esterification of pectin were also obviously decreased in the endosperm of naa15. In summary, we identified a large number of DEGs and investigated the features of cell walls during endosperm cellularization and embryonic differentiation, which provided important information on transcription and gene expression to reveal their regulatory mechanisms.

Transcriptomic insights into the molecular mechanism of wheat response to stripe rust fungus

The wheat crop (Triticum aestivum L.) is the widely cultivated and most important staple foods of worlds. Stripe (yellow) rust is prompted by Puccinia striiformis f. sp. tritici (Pst) to reduces the yield and grain quality of the wheat significantly. Although many resistant cultivars have been successfully used in wheat breeding, the size of the regulating network and the underlying molecular mechanisms of wheat to response Pst still unknown. Therefore, in order to identify differentially expression genes (DEGs) and the regulate network related to Pst resistance, 15 cDNA libraries were constructed from wheat with CYR34 infection. In this study, a highly susceptible cv. Chuanyu12 (CY12) was used to study the transcriptome profiles after being inoculated with Pst physiological race CYR34. The DEGs were investigated at 24h, 48h, 72h, and 7 days post-inoculation. Certain key genes and pathways of response for Pst-CYR34 in CY12 were identified. The results revealed that Pst-CYR34 inhibited the DEGs related to energy metabolism, biosynthesis, carbon fixation, phenylalanine metabolism, and plant hormone signaling pathways after post-inoculation at 24h, 48h, 72h, and 7d. Light-harvesting chlorophyll protein complex in photosystem I and photosystem II; F-type ATPase, cytochrome b6/f/complex, and photosynthetic electron transport; ethylene, salicylic acid (SA), and jasmonic acid (JA); and lignin and flavonoids biosynthesis in CY12 are among the down-regulated DEGs. The expression patterns of these DEGs were verified via Quantitative Real-time PCR analysis. Our results give insights into the foundation for further exploring the molecular mechanisms regulating networks of Pst response and opens the door for bread wheat Pst resistance breeding.

Physiological and Comparative Transcriptome Analyses of the High-Tillering Mutant mtn1 Reveal Regulatory Mechanisms in the Tillering of Centipedegrass (Eremochloa ophiuroides (Munro) Hack.).

Tillering is a key factor that determines the reproductive yields of centipedegrass, which is an important perennial warm-season turfgrass. However, the regulatory mechanism of tillering in perennial plants is poorly understood, especially in perennial turfgrasses. In this study, we created and characterised a cold plasma-mutagenised centipedegrass mutant, mtn1 (more tillering number 1). Phenotypic analysis showed that the mtn1 mutant exhibited high tillering, short internodes, long seeds and a heavy 1000-seed weight. Then, a comparative transcriptomic analysis of the mtn1 mutant and wild-type was performed to explore the molecular mechanisms of centipedegrass tillering. The results revealed that plant hormone signalling pathways, as well as starch and sucrose metabolism, might play important roles in centipedegrass tillering. Hormone and soluble sugar content measurements and exogenous treatment results validated that plant hormones and sugars play important roles in centipedegrass tiller development. In particular, the overexpression of the auxin transporter ATP-binding cassette B 11 (EoABCB11) in Arabidopsis resulted in more branches. Single nucleotide polymorphisms (SNPs) were also identified, which will provide a useful resource for molecular marker-assisted breeding in centipedegrass. According to the physiological characteristics and transcriptional expression levels of the related genes, the regulatory mechanism of centipedegrass tillering was systematically revealed. This research provides a new breeding resource for further studies into the molecular mechanism that regulates tillering in perennial plants and for breeding high-tillering centipedegrass varieties.

The SlTPL3-SlWUS module regulates multi-locule formation in tomato by modulating auxin and gibberellin levels in the shoot apical meristem.

Malformed fruits depreciate a plant's market value. In tomato (Solanum lycopersicum), fruit malformation is associated with the multi-locule trait, which involves genes regulating shoot apical meristem (SAM) development. The expression pattern of TOPLESS3 (SlTPL3) throughout SAM development prompted us to investigate its functional significance via RNA interference (RNAi) and clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease 9 (Cas9)-mediated gene editing. Lower SlTPL3 transcript levels resulted in larger fruits with more locules and larger SAMs at the 5 d after germination (DAG5) stage. Differentially expressed genes in the SAM of wild-type (WT) and SlTPL3-RNAi plants, identified by transcriptome deep sequencing (RNA-seq), were enriched in the gibberellin (GA) biosynthesis and plant hormone signaling pathways. Moreover, exogenous auxin and paclobutrazol treatments rescued the multi-locule phenotype, indicating that SlTPL3 affects SAM size by mediating auxin and GA levels in the SAM. Furthermore, SlTPL3 interacted with WUSCHEL (SlWUS), which plays an important role in SAM size maintenance. We conducted RNA-seq and DNA affinity purification followed by sequencing (DAP-seq) analyses to identify the genes regulated by SlTPL3 and SlWUS in the SAM and to determine how they regulate SAM size. We detected 24 overlapping genes regulated by SlTPL3 and SlWUS and harboring an SlWUS-binding motif in their promoters. Furthermore, functional annotation revealed a notable enrichment for functions in auxin transport, auxin signal transduction, and GA biosynthesis. Dual-luciferase assays also revealed that SlTPL3 enhances SlWUS-mediated regulation (repression and activation) of SlPIN3 and SlGA2ox4 transcription, indicating that the SlTPL3-SlWUS module regulates SAM size by mediating auxin distribution and GA levels, and perturbations of this module result in enlarged SAM. These results provide novel insights into the molecular mechanism of SAM maintenance and locule formation in tomato and highlight the SlTPL3-SlWUS module as a key regulator.

Insights into the defense mechanisms involved in the induction of resistance against black spot of cherry tomatoes by Pichia caribbica

Our previous study showed that Pichia caribbica could alleviate black spot of cherry tomatoes. This study aimed to explore the comprehensive mechanisms involved in the induced disease resistance of cherry tomatoes by this yeast. The results indicated that P. caribbica increased the activities of defense-related enzymes and enzymes of phenylpropanoid pathway including polyphenol oxidase, chitinase, β-1,3-glucanase, phenylalanine ammonia-lyase and cinnamate-4-hydroxylase in the fruits. Considering together with transcriptome analysis results, it was suggested that P. caribbica triggered mitogen-activated protein kinase, Ca2+ and plant hormone signaling pathways, up-regulated genes related to reactive oxygen species scavenging, induced defense-related genes and enzyme activities, and stimulated genes and the activities of enzymes involved in secondary metabolite synthesis to accumulate total phenols, lignin and flavonoids, thus enhancing the resistance of cherry tomatoes against black spot. This study will provide new insights into the underlying mechanisms involved in induced disease resistance of cherry tomatoes by antagonistic yeast.

Tissue-specific transcriptional analysis outlines calcium-induced core metabolic changes in sweet cherry fruit

The role of calcium in fruit ripening has been established, however knowledge regarding the molecular analysis at fruit tissue-level is still lacking. To address this, we examined the impact of foliar-applied calcium (0.5% CaCl2) in the ripening metabolism in skin and flesh tissues of the sweet cherry ‘Tragana Edessis’ fruit at the harvest stage. Exogenously applied calcium increased endogenous calcium level in flesh tissue and reduced fruit respiration rate and cracking traits. Fruit metabolomic along with transcriptomic analysis unraveled common and tissue-specific metabolic pathways associated with calcium feeding. Treatment with calcium diminished several alcohols (arabitol, sorbitol), sugars (fructose, maltose), acids (glyceric acid, threonic acid) and increased ribose and proline in both fruit tissues. Moreover, numerous primary metabolites, such as proline and galacturonic acid, were differentially accumulated in calcium-exposed tissues. Calcium-affected genes that involved in ubiquitin/ubl conjugation and cell wall biogenesis/degradation were differentially expressed between skin and flesh samples. Notably, skin and flesh tissues shared common calcium-responsive genes and exhibited substantial similarity in their expression patterns. In both tissues, calcium activated gene expression, most strongly those involved in plant-pathogen interaction, plant hormone signaling and MAPK signaling pathway, thus affecting related metabolic processes. By contrast, calcium depressed the expression of genes related to TCA cycle, oxidative phosphorylation, and starch/sucrose metabolism in both tissues. This work established both calcium-driven common and specialized metabolic suites in skin and flesh cherry tissues, demonstrating the utility of this approach to characterize fundamental aspects of calcium in fruit physiology.

Analysis of Floral Organ Development and Sex Determination in Schisandra chinensis by Scanning Electron Microscopy and RNA-Sequencing.

S. chinensis is a typical monoecious plant, and the number and development of female flowers determines the yield of S. chinensis. Due to a lack of genetic information, the molecular mechanism of sex differentiation in S. chinensis remains unclear. In this study, the combination of scanning electron microscopy (SEM) and RNA sequencing (RNA-seq) was used to understand the way of sex differentiation of S. chinensis and to mine the related genes of sex determination. The result shows the development of male and female S. chinensis flowers was completed at the same time, the unisexual S. chinensis flowers did not undergo a transition stage between sexes, and sex may have been determined at an early stage in flower development. The results of the gene function analysis of the plant hormone signaling pathway and sucrose metabolism pathway suggest that auxin and JA could be the key hormones for sex differentiation in S. chinensis, and sucrose may promote pollen maturation at the later stage of male flower development. Two AGAMOUS (GAG) genes, 10 AGAMOUS-like MADS-box (AGLs) genes, and the MYB, NAC, WRKY, bHLH, and Trihelix transcription factor families may play important roles in sex determination in S. chinensis. Taken together, the present findings provide valuable genetic information on flower development and sex determination in S. chinensis.

Integrated transcriptome and metabolome analyses reveal the adaptation of Antarctic moss Pohlia nutans to drought stress.

Most regions of the Antarctic continent are experiencing increased dryness due to global climate change. Mosses and lichens are the dominant vegetation of the ice-free areas of Antarctica. However, the molecular mechanisms of these Antarctic plants adapting to drought stress are less documented. Here, transcriptome and metabolome analyses were employed to reveal the responses of an Antarctic moss (Pohlia nutans subsp. LIU) to drought stress. We found that drought stress made the gametophytes turn yellow and curled, and enhanced the contents of malondialdehyde and proline, and the activities of antioxidant enzymes. Totally, 2,451 differentially expressed genes (DEGs) were uncovered under drought treatment. The representative DEGs are mainly involved in ROS-scavenging and detoxification, flavonoid metabolism pathway, plant hormone signaling pathway, lipids metabolism pathway, transcription factors and signal-related genes. Meanwhile, a total of 354 differentially changed metabolites (DCMs) were detected in the metabolome analysis. Flavonoids and lipids were the most abundant metabolites and they accounted for 41.53% of the significantly changed metabolites. In addition, integrated transcriptome and metabolome analyses revealed co-expression patterns of flavonoid and long-chain fatty acid biosynthesis genes and their metabolites. Finally, qPCR analysis demonstrated that the expression levels of stress-related genes were significantly increased. These genes included those involved in ABA signaling pathway (NCED3, PP2C, PYL, and SnAK2), jasmonate signaling pathway (AOC, AOS, JAZ, and OPR), flavonoid pathway (CHS, F3’,5’H, F3H, FLS, FNS, and UFGT), antioxidant and detoxifying functions (POD, GSH-Px, Prx and DTX), and transcription factors (ERF and DREB). In summary, we speculated that P. nutans were highly dependent on ABA and jasmonate signaling pathways, ROS scavenging, flavonoids and fatty acid metabolism in response to drought stress. These findings present an important knowledge for assessing the impact of coastal climate change on Antarctic basal plants.

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.

Mitogen-Activated Protein Kinase Is Involved in Salt Stress Response in Tomato (Solanum lycopersicum) Seedlings.

Salt stress impairs plant growth and development, thereby causing low yield and inferior quality of crops. In this study, tomato (Solanum lycopersicum L. ‘Micro-Tom’) seedlings treated with different concentrations of sodium chloride (NaCl) were investigated in terms of decreased plant height, stem diameter, dry weight, fresh weight, leaves relative water content and root activity. To reveal the response mechanism of tomato seedlings to salt stress, the transcriptome of tomato leaves was conducted. A total of 6589 differentially expressed genes (DEGs) were identified and classified into different metabolic pathways, especially photosynthesis, carbon metabolism, biosynthesis of amino acids and mitogen-activated protein kinase (MAPK) signaling pathway. Of these, approximately 42 DEGs were enriched in the MAPK signaling pathway, most of which mainly included plant hormone, hydrogen peroxide (H2O2), wounding and pathogen infection signaling pathways. To further explore the roles of MAPK under salt stress, MAPK phosphorylation inhibitor SB203580 (SB) was applied. We found that SB further decreased endogenous jasmonic acid, abscisic acid and ethylene levels under salt stress condition. Additionally, in comparison with NaCl treatment alone, SB + NaCl treatment reduced the content of O2− and H2O2 and the activities of antioxidant enzyme and downregulated the expression levels of genes related to pathogen infection. Together, the results revealed that MAPK might be involved in the salinity response of tomato seedlings by regulating hormone balance, ROS metabolism, antioxidant capacity and plant immunity.

Research advances in the plant TCP transcription factors

<p indent="0mm">Transcription factors (TFs) are a group of protein molecules that can bind to a specific gene with a specific sequence specificity, thus ensuring that the target gene is expressed at a specific time and in space at a specific intensity. The plant-specific TFs of the TCP family (for Teosinte branched 1 in corn, CYCLOIDEA (CYC) in snapdragon (<italic>Antirrhinum majus</italic>) and PROLIFERATING CELL FACTOR 1/2 in rice) are characterized by an N-terminal non-canonical beta helix-loop-helix (bHLH) domain known as the TCP domain, and regulate the spatiotemporal expression of genes by binding to specific promoter sequences. TCP TFs play important roles in regulating the development of roots, stems, leaves, flowers, fruits, and vascular tissues, and participate in physiological processes such as plant secondary metabolism, plant immunity, and the responses to biotic and abiotic stress. The TCP TF family is conserved and widespread in plants. Based on the TCP domain sequence, TCP TFs are categorized into Class I and Class II; based on the amino acid sequence of the basic region and bHLH domain, the Class II TCP TFs can be further divided into CINCINNATA (CIN)-like TCPs (CIN) and CYC-like TCPs (CYC-C). In recent years, increasing numbers of studies have shed light on how TCP TFs regulate plant growth and development, especially on the functions of upstream regulators and downstream target genes. Plants have evolved multiple ways to accurately regulate their downstream related factors, and their own gene expression is also strictly regulated. TCP genes have also been analyzed in various plants and found to take part in the regulation of circadian rhythms and the biosynthesis and signaling pathways of plant hormones, among other functions. Other studies have investigated the regulatory relationships between TCP TFs and microRNAs. Additionally, members of the TCP family are often functionally redundant, making it difficult to study their functions; therefore, gene-editing technology and high-throughput sequencing have opened up new avenues to study this TF family. Here, we summarize recent advances in our understanding of how TCP activity is translated to the dynamic spatiotemporal control of cell-fate determination, life-cycle transitions, dormancy release, seed germination, leaf development, outgrowth of shoot branches, growth-repressing microRNAs, and interactions with the chromatin remodeling machinery to modulate phytohormone responses. Furthermore, we discuss existing problems and future directions in TCP research, in particular the role of TCP-related protein modification in plant growth and development and stress responses. Finally, we provide perspectives on the future research that is needed to gain a deep understanding of the diverse regulatory networks of TCP TFs in plant growth and development.