CLV3-CLV1 signaling governs flower primordia outgrowth across environmental temperatures.

The initiation and outgrowth of floral primordia are critical for flower formation and reproductive success; however, the underlying mechanisms are still unclear. Two reports (Jones et al.; John et al.) shed light on how CLV3-CLV1 signaling promoted flower primordia formation and outgrowth by regulating auxin biosynthesis under distinct environmental temperatures.

Red light induces salicylic acid accumulation by activating CaHY5 to enhance pepper resistance against Phytophthora capsici.

Pepper (Capsicum annuum L.) is frequently challenged by various pathogens, among which Phytophthora capsici is the most devastating to pepper production. Red light signal acts as a positive induction of plant resistance against multiple pathogens. However, little is known about how the red light signal affects pepper resistance to P. capsici infection (PCI). Here, we report that red light regulates salicylic acid (SA) accumulation by activating elongated hypocotyl5 (CaHY5), a basic leucine zipper (bZIP) transcription factor, thereby decreasing pepper susceptibility to PCI. Exogenous SA treatment reduced pepper susceptibility to PCI, while silencing of CaPHYB (a red light photoreceptor) increased its susceptibility. PCI significantly induced CaHY5 expression, and silencing of CaHY5 reduced SA accumulation, accompanied by decreases in the expression levels of phenylalanine ammonia-lyase 3 (CaPAL3), CaPAL7, pathogenesis-related 1 (CaPR1), and CaPR1L, which finally resulted in higher susceptibility of pepper to PCI. Moreover, CaHY5 was found to activate the expression of CaPAL3 and CaPAL7, which are essential for SA biosynthesis, by directly binding to their promoters. Further analysis revealed that exogenous SA treatment could restore the resistance of CaHY5-silenced pepper plants to PCI. Collectively, this study reveals a critical mechanism through which red light induces SA accumulation by regulating CaHY5-mediated CaPAL3 and CaPAL7 expression, leading to enhanced resistance to PCI. Moreover, red light-induced CaHY5 regulates pepper resistance to PCI, which may have implications for PCI control in protected vegetable production.

Comprehensive analysis of the UDP-glucuronate decarboxylase (UXS) gene family in tobacco and functional characterization of NtUXS16 in Golgi apparatus in Arabidopsis.

BACKGROUND: UDP-glucuronate decarboxylase (also named UXS) converts UDP-glucuronic acid (UDP-GlcA) to UDP-xylose (UDP-Xyl) by decarboxylation of the C6-carboxylic acid of glucuronic acid. UDP-Xyl is an important sugar donor that is required for the synthesis of plant cell wall polysaccharides. RESULTS: In this study, we first carried out the genome-wide identification of NtUXS genes in tobacco. A total of 17 NtUXS genes were identified, which could be divided into two groups (Group I and II), and the Group II UXSs can be further divided into two subgroups (Group IIa and IIb). Furthermore, the protein structures, intrachromosomal distributions and gene structures were thoroughly analyzed. To experimentally verify the subcellular localization of NtUXS16 protein, we transformed tobacco BY-2 cells with NtUXS16 fused to the monomeric red fluorescence protein (mRFP) at the C terminus under the control of the cauliflower mosaic virus (CaMV) 35S promoter. The fluorescent signals of NtUXS16-mRFP were localized to the medial-Golgi apparatus. Contrary to previous predictions, protease digestion analysis revealed that NtUXS16 is not a type II membrane protein. Overexpression of NtUXS16 in Arabidopsis seedling in darkness led to a significant increase in hypocotyl length and a reduction in root length compared with the wild type. In summary, these results suggest Golgi apparatus localized-NtUXS16 plays an important role in hypocotyl and root growth in the dark. CONCLUSION: Our findings facilitate our understanding of the novel functions of NtUXS16 and provide insights for further exploration of the biological roles of NtUXS genes in tobacco.

Spectral light quality regulates the morphogenesis, architecture, and flowering in pepper (Capsicum annuum L.).

Transparent plastic films with poor light transmittance seriously affect the mass composition of visible light in many greenhouses, which leads to the reduction of photosynthesis in vegetable crops. Understanding the regulatory mechanisms of monochromatic light in the vegetative and reproductive growth of vegetable crops is of great importance for the application of light-emitting diodes (LEDs) in the greenhouse. In this study, three monochromatic light treatments (red-, green- and blue-light) were simulated by using LEDs to explore light quality-dependent regulation from the stage of seedling to flowering in pepper (Capsicum annuum L.). The results showed that light quality-dependent regulation guides the growth and morphogenesis in pepper plants. Red- and blue-light played opposite roles in determining the plant height, stomatal density, axillary bud growth, photosynthetic characteristics, flowering time and hormone metabolism, while green light treatment resulted in taller plants and fewer branches, which was similar to the red-light treatment. The weighted correlation network analysis (WGCNA) based on mRNA-seq results revealed that the two modules named "MEred" and "MEmidnightblue" were positively correlated with red- and blue-light treatment, respectively, exhibiting high correlations with the traits such as plant hormone content, branching and flowering. Moreover, our results suggest that the light response factor ELONGATED HYPOCOTYL 5 (HY5) is essential for blue light-induced plant growth and development by regulating photosynthesis in pepper plants. Hence, this study uncovers crucial molecular mechanisms of how light quality determines the morphogenesis, architecture, and flowering in pepper plants, thus providing a basic concept of manipulating light quality to regulate pepper plant growth and flowering under greenhouse conditions.

Characterization of the B-BOX gene family in pepper and the role of CaBBX14 in defense response against Phytophthora capsici infection.

The B-box (BBX) transcription factors are widely implicated in plant growth, development, and response to various biotic and abiotic stresses. However, their roles in the response of pepper to Phytophthora capsici infection (PCI) remain largely unexplored. Here, we report a total of 25 CaBBX genes with an uneven distribution were identified in pepper genome, and their characteristics, phylogenetic relationships, gene structures, conserved domains, and expression profiles were validated. CaBBXs were classified into five major clades (I to V) based on their phylogenetic relationships and conserved domains (presence of one or two B-box domains and a CCT domain). Gene duplication analysis demonstrated that there are two segmental duplication events but no tandem duplication event within pepper genome. Conserved motif and gene structure analysis revealed that the CaBBXs in the same clade have relatively similar motif arrangements and exon-intron patterns. Expression analysis revealed that the CaBBX genes have different expression levels in various tissues, and some of which were significantly induced during PCI and exogenous salicylic acid (SA) treatment. Among them, CaBBX14 displayed remarkable changed expression during PCI and SA treatment. The silencing of CaBBX14 increases pepper susceptibility to PCI, and also decreases in SA content and expression of pathogenesis-related (PR) and SA-related genes compared with control plants. Together, these findings advance our knowledge base on biological functions of CaBBXs in pepper during PCI through the SA signaling pathway, and we provide an example demonstrating that the potential of CaBBX14 to improve pepper resistance to PCI.

Post-Harvest LED Light Irradiation Affects Firmness, Bioactive Substances, and Amino Acid Compositions in Chili Pepper (Capsicum annum L.).

Chili pepper is an important vegetable and spice crop with high post-harvest deteriorations in terms of commercial and nutritional quality. Light-emitting diodes (LEDs) are eco-friendly light sources with various light spectra that have been demonstrated to improve the shelf-life of various vegetables by manipulating light quality; however, little is known about their effects on the post-harvest nutritional quality of chili peppers. This study investigated the effects of different LED lightings on the post-harvest firmness and nutritional quality of chili peppers. We found that red and blue light could increase the content of capsaicinoids, whereas white and red light could increase the essential and aromatic amino acid (AA) content in pepper. Nonetheless, the influence of light treatments on AA contents and compositions depends strongly on the pepper genotype, which was reflected by total AA content, single AA content, essential AA ratio, delicious AA ratio, etc., that change under different light treatments. Additionally, light affected fruit firmness and the content of nutrients such as chlorophyll, vitamin C, and total carotenoids, to varying degrees, depending on pepper genotypes. Thus, our findings indicate that LED-light irradiation is an efficient and promising strategy for preserving or improving the post-harvest commercial and nutritional quality of pepper fruit.

Identification of the 12-oxophytoeienoic acid reductase (OPR) gene family in pepper (Capsicum annuum L.) and functional characterization of CaOPR6 in pepper fruit development and stress response.

The 12-oxophytoeienoic acid reductase (OPR) is a kind of enzyme in the octadecanoid biosynthesis pathway that determines the biosynthesis of jasmonic acid. Although the roles of OPRs have been extensively studied in several crop plants, little is known about the biological functions of OPR-encoding genes in Capsicum annuum plants. In this study, seven OPR family genes (CaOPR1-7) were identified from the C. annuum genome. The physical and chemical properties of CaOPR1-7 were further analyzed, including gene expression patterns, promoter elements, and chromosomal locations. The results showed that the seven CaOPR homologues could be divided into two subgroups, and CaOPR6 was highly similar to AtOPR3 in Arabidopsis. The expression of CaOPR6 was significantly induced by various stresses such as cold, salt, and pathogen infection, indicating that CaOPR6 plays important roles in response to abiotic and biotic stresses. Overall, these findings improve the understanding of the biological functions of CaOPR6 in the development of pepper fruit and stress response of pepper plants, and facilitate further studies on the molecular biology of OPR proteins in Solanaceae vegetables.

Molecular Characterization of Mg-Chelatase CHLI Subunit in Pea (Pisum sativum L.).

As a rate-limiting enzyme for chlorophyll biosynthesis, Mg-chelatase is a promising target for improving photosynthetic efficiency. It consists of CHLH, CHLD, and CHLI subunits. In pea (Pisum sativum L.), two putative CHLI genes (PsCHLI1 and PsCHLI2) were revealed recently by the whole genome sequencing, but their molecular features are not fully characterized. In this study, PsCHLI1 and PsCHLI2 cDNAs were identified by PCR-based cloning and sequencing. Phylogenetic analysis showed that PsCHLIs were derived from an ancient duplication in legumes. Both PsCHLIs were more highly expressed in leaves than in other organs and downregulated by abscisic acid and heat treatments, while PsCHLI1 was more highly expressed than PsCHLI2. PsCHLI1 and PsCHLI2 encode 422- and 417-amino acid proteins, respectively, which shared 82% amino acid identity and were located in chloroplasts. Plants with a silenced PsCHLI1 closely resembled PsCHLI1 and PsCHLI2 double-silenced plants, as both exhibited yellow leaves with barely detectable Mg-chelatase activity and chlorophyll content. Furthermore, plants with a silenced PsCHLI2 showed no obvious phenotype. In addition, the N-terminal fragment of PsCHLI1 (PsCHLI1N, Val63-Cys191) and the middle fragment of PsCHLI1 (PsCHLI1M, Gly192-Ser336) mediated the formation of homodimers and the interaction with CHLD, respectively, while active PsCHLI1 was only achieved by combining PsCHLI1N, PsCHLI1M, and the C-terminal fragment of PsCHLI1 (Ser337-Ser422). Taken together, PsCHLI1 is the key CHLI subunit, and its peptide fragments are essential for maintaining Mg-chelatase activity, which can be used to improve photosynthetic efficiency by manipulating Mg-chelatase in pea.

Anthocyanin-mediated arsenic tolerance in plants.

Plants detoxify toxic metal(loid)s by accumulating diverse metabolites. Beside scavenging excess reactive oxygen species (ROS) induced by metal(loid)s, some metabolites chelate metal(loid) ions. Classically, thiol-containing compounds, especially glutathione (GSH) and phytochelatins (PCs) are thought to be the major chelators that conjugate with metal(loid)s in the cytoplasm followed by transport and sequestration in the vacuole. In addition to this classical detoxification pathway, a role for secondary metabolites in metal(loid) detoxification has recently emerged. In particular, anthocyanins, a kind of flavonoids with ROS scavenging potential, contribute to enhanced arsenic tolerance in several plant species. Evidence is accumulating that, in analogy to GSH and PCs, anthocyanins may conjugate with arsenic followed by vacuolar sequestration in the detoxification event. Exogenous application or endogenous accumulation of anthocyanins enhances arsenic tolerance, leading to improved plant growth and productivity. The application of some plant hormones and signaling molecules stimulates endogenous anthocyanin synthesis which confers tolerance to arsenic stress. Anthocyanin biosynthesis is transcriptionally regulated by several transcription factors, including myeloblastosis (MYBs). The light-regulated transcription factor elongated hypocotyl 5 (HY5) also affects anthocyanin biosynthesis, but its role in arsenic tolerance remains elusive. Here, we review the mechanism of arsenic detoxification in plants and the potential role of anthocyanins in arsenic tolerance beyond the classical points of view. Our analysis proposes that anthocyanin manipulation in crop plants may ensure sustainable crop yield and food safety in the marginal lands prone to arsenic pollution.

Light regulation of potassium in plants.

Essential macronutrient potassium (K) and environmental signal light regulate a number of vital plant biological processes related to growth, development, and stress response. Recent research has shown connections between the perception of light and the regulation of K in plants. Photoreceptors-mediated wavelength-specific light perception activates signaling cascades which mediate stomatal movement by altering K+influx/efflux via K+ channels in the guard cells. The quality, intensity, and duration of light affect the regulation of K nutrition and crop quality. Blue/red illumination or red combined blue light treatment increases the expression levels of K transporter genes, K uptake and accumulation, leading to increased lycopene synthesis and improved fruit color in tomato. Despite the commonalities of light and K in multiple functions, our understanding of light regulation of K and associated physiological and molecular processes is fragmentary. In this review, we take a look at the light-controlled K uptake and utilization in plants and propose working models to show potential mechanisms. We discuss major light signaling components, their possible involvement in K nutrition, stomatal movement and crop quality by linking the perception of light signal and subsequent regulation of K. We also pose some outstanding questions to guide future research. Our analysis suggests that the enhancement of K utilization efficiency by manipulation of light quality and light signaling components can be a promising strategy for K management in crop production.

Characterization of Phytochrome-Interacting Factor Genes in Pepper and Functional Analysis of CaPIF8 in Cold and Salt Stress.

As a subfamily of basic helix-loop-helix (bHLH) transcription factors, phytochrome-interacting factors (PIFs) participate in regulating light-dependent growth and development of plants. However, limited information is available about PIFs in pepper. In the present study, we identified six pepper PIF genes using bioinformatics-based methods. Phylogenetic analysis revealed that the PIFs from pepper and some other plants could be divided into three distinct groups. Motif analysis revealed the presence of many conserved motifs, which is consistent with the classification of PIF proteins. Gene structure analysis suggested that the CaPIF genes have five to seven introns, exhibiting a relatively more stable intron number than other plants such as rice, maize, and tomato. Expression analysis showed that CaPIF8 was up-regulated by cold and salt treatments. CaPIF8-silenced pepper plants obtained by virus-induced gene silencing (VIGS) exhibited higher sensitivity to cold and salt stress, with an obvious increase in relative electrolyte leakage (REL) and variations in the expression of stress-related genes. Further stress tolerance assays revealed that CaPIF8 plays different regulatory roles in cold and salt stress response by promoting the expression of the CBF1 gene and ABA biosynthesis genes, respectively. Our results reveal the key roles of CaPIF8 in cold and salt tolerance of pepper, and lay a solid foundation for clarifying the biological roles of PIFs in pepper and other plants.

BrcuHAC1 is a histone acetyltransferase that affects bolting development in Chinese flowering cabbage.

Histone acetylation is an important posttranslational modification associated with gene activation. In Arabidopsis, histone acetyltransferase 1 (HAC1) can promote flowering by regulating the transcription of FLOWERING LOCUS C (FLC), a major floral repressor. The size of the full-length cDNA and genomic DNA sequences of the histone acetyltransferase 1 gene (BrcuHAC1) in Chinese flowering cabbage (Brassica rapa syn. campestris ssp. chinensis var. utilis) were 5846 bp and 7376 bp, with an open reading frame (ORF) coding for a peptide with 1689 amino acids. The expression levels of BrcuHAC1 in different tissues and different developmental stages were as follows: flower>leaf>stem>root, and completed bolting and flowering stage>5th true leaf-stage>4th true leaf-stage>3rd true leaf-stage>2nd true leaf-stage>1st true leaf-stage. Silencing of BrcuHAC1 resulted in slow growth, and delayed bolting and flowering time in Chinese flowering cabbage. Molecular analysis showed that the mRNA level of FLC was increased, indicating that the delayed flowering phenomenon was mediated by FLC in the silenced group. In contrast, the expression levels of the autonomous-pathway genes were not significantly affected in the silenced group. In addition, the histone modification of FLC chromatin was also not affected in the silenced group. FLC is not the direct target gene of BrcuHAC1. However, BrcuHAC1 may affect the bolting and flowering time of Chinese flowering cabbage through the epigenetic modification of upstream factors of FLC.

Mechanisms of elevated CO2-induced thermotolerance in plants: the role of phytohormones.

Rising atmospheric CO2 is a key driver of climate change, intensifying drastic changes in meteorological parameters. Plants can sense and respond to changes in environmental parameters including atmospheric CO2 and temperatures. High temperatures beyond the physiological threshold can significantly affect plant growth and development and thus attenuate crop productivity. However, elevated atmospheric CO2 can mitigate the deleterious effects of heat stress on plants. Despite a large body of literature supporting the positive impact of elevated CO2 on thermotolerance, the underlying biological mechanisms and precise molecular pathways that lead to enhanced tolerance to heat stress remain largely unclear. Under heat stress, elevated CO2-induced expression of respiratory burst oxidase homologs (RBOHs) and reactive oxygen species (ROS) signaling play a critical role in stomatal movement, which optimizes gas exchange to enhance photosynthesis and water use efficiency. Notably, elevated CO2 also fortifies antioxidant defense and redox homeostasis to alleviate heat-induced oxidative damage. Both hormone-dependent and independent pathways have been shown to mediate high CO2-induced thermotolerance. The activation of heat-shock factors and subsequent expression of heat-shock proteins are thought to be the essential mechanism downstream of hormone and ROS signaling. Here we review the role of phytohormones in plant response to high atmospheric CO2 and temperatures. We also discuss the potential mechanisms of elevated CO2-induced thermotolerance by focusing on several key phytohormones such as ethylene. Finally, we address some limitations of our current understanding and the need for further research to unveil the yet-unknown crosstalk between plant hormones in mediating high CO2-induced thermotolerance in plants.

Genome-Wide Characterization of B-Box Gene Family and Its Roles in Responses to Light Quality and Cold Stress in Tomato.

Perceiving incoming environmental information is critical for optimizing plant growth and development. Multiple B-box proteins (BBXs) play essential roles in light-dependent developmental processes in plants. However, whether BBXs function as a signal integrator between light and temperature in tomato plants remains elusive. In this study, 31 SlBBX genes were identified from the newly released tomato (Solanum lycopersicum) genome sequences and were clustered into five subgroups. Gene structure and protein motif analyses showed relatively high conservation of closely clustered SlBBX genes within each subgroup; however, genome mapping analysis indicated the uneven distribution of the SlBBX genes on tomato chromosomes. Promoter cis-regulatory elements prediction and gene expression indicated that SlBBX genes were highly responsive to light, hormones, and stress conditions. Reverse genetic approaches revealed that disruption of SlBBX7, SlBBX9, and SlBBX20 largely suppressed the cold tolerance of tomato plants. Furthermore, the impairment of SlBBX7, SlBBX9, and SlBBX20 suppressed the photosynthetic response immediately after cold stress. Due to the impairment of non-photochemical quenching (NPQ), the excess photon energy and electron flow excited by low temperature were not consumed in SlBBX7-, SlBBX9-, and SlBBX20- silenced plants, leading to the over reduction of electron carriers and damage of the photosystem. Our study emphasized the positive roles of light signaling transcription factors SlBBXs in cold tolerance in tomato plants, which may improve the current understanding of how plants integrate light and temperature signals to adapt to adverse environments.

Mechanisms of silicon-induced fungal disease resistance in plants.

Silicon (Si) acts as a beneficial element for plant growth and provides protection against abiotic and biotic stresses. Despite numerous reports on the beneficial role of Si in enhancing plant resistance to fungal pathogens, the underlying mechanisms remain largely unclear. Silicon shows antifungal activity; however, Si-induced improved disease resistance is partly manifested by the formation of Si polymerized mechanical obstruction under the cuticle and in cell walls, which prevents fungal ingress. Moreover, rapid production of defense compounds through secondary metabolic pathways is thought to be a key mechanism of Si-induced chemical defense against fungal pathogens beyond the physical barrier. Besides, improved mineral nutrition assures the healthy status of Si-supplied plants and a healthy plant exhibits better photosynthetic potential, antioxidant capacity and disease resistance. Multiple plant hormones and their crosstalk mediate the Si-induced basal as well as induced resistance; nonetheless, how root uptake of Si systemically modulates resistance to foliar diseases in low Si accumulating plants, needs in-depth investigation. Recent studies also indicate that Si influences effector-triggered immunity by affecting host recognition and/or limiting receptor-effector interactions. Here we review the role of Si in plant response to fungal pathogens. We also discuss and propose potential mechanisms of Si-induced enhanced disease resistance in plants. Finally, we identify some limitations of research approaches in addressing the beneficial roles of Si in biotic stress management.

The histone variant Sl_H2A.Z regulates carotenoid biosynthesis and gene expression during tomato fruit ripening.

The conserved histone variant H2A.Z is essential for transcriptional regulation; defense responses; and various biological processes in plants, such as growth, development, and flowering. However, little is known about how H2A.Z affects the developmental process and ripening of tomato fruits. Here, we utilized the CRISPR/Cas9 gene-editing system to generate a sl_hta9 sl_hta11 double-mutant, designated sl_h2a.z, and found that these two mutations led to a significant reduction in the fresh weight of tomato fruits. Subsequent messenger RNA (mRNA)-seq results showed that dysfunction of Sl_H2A.Z has profound effects on the reprogramming of genome-wide gene expression at different developmental stages of tomato fruits, indicating a ripening-dependent correlation between Sl_H2A.Z and gene expression regulation in tomato fruits. In addition, the expression of three genes, SlPSY1, SlPDS, and SlVDE, encoding the key enzymes in the biosynthesis pathway of carotenoids, was significantly upregulated in the later ripening stages, which was consistent with the increased contents of carotenoids in sl_h2a.z double-mutant fruits. Overall, our study reveals a role of Sl_H2A.Z in the regulation of carotenoids and provides a resource for the study of Sl_H2A.Z-dependent gene expression regulation. Hence, our results provide a link between epigenetic regulation via histone variants and fruit development, suggesting a conceptual framework to understand how histone variants regulate tomato fruit quality.

Role of ethylene crosstalk in seed germination and early seedling development: A review.

Seed germination and early seedling development are two critical phases in plant lifecycle that largely determine crop yield. Phytohormones play an essential role in governing these developmental processes; of these, ethylene (ET; C2H4), the smallest gaseous hormone, plays a major role via crosstalk with other hormones. Typically, the mechanism of hormone (for instance, auxin, cytokinins, ET, and gibberellins) action is determined by cellular context, revealing either synergistic or antagonistic relations. Significant progress has been made, so far, on unveiling ET crosstalk with other hormones and environmental signals, such as light. In particular, stimulatory and inhibitory effects of ET on hypocotyl growth in light and dark, respectively, and its interaction with other hormones provide an ideal model to study the growth-regulatory pathways. In this review, we aim at exploring the mechanisms of multifarious phenomena that occur via ET crosstalk during the germination of seeds (overcoming dormancy), and all through the development of seedlings. Understanding the remarkably complex mechanism of ET crosstalk that emerges from the interaction between hormones and other molecular players to modulate plant growth, remains a challenge in plant developmental biology.

Genome-wide characterization and expression analysis of the Dof gene family related to abiotic stress in watermelon.

The plant DNA-binding with one finger (Dof) gene family is a class of plant-specific transcription factors that play vital roles in many biological processes and stress responses. In the present study, a total of 36 ClDof genes were identified in the watermelon genome, which were unevenly distributed on 10 chromosomes. Phylogenetic analysis showed that the ClDof proteins could be divided into nine groups, and the members in a particular group had similar motif arrangement and exon-intron structure. Synteny analysis indicated the presence of a large number of syntenic relationship events between watermelon and cucumber. In promoter analysis, five kinds of stress-related and nine kinds of hormone-related cis-elements were identified in the promoter regions of ClDof genes. We then analyzed the expression patterns of nine selected ClDof genes in eight specific tissues by qRT-PCR, and the results showed that they have tissue-specific expression patterns. We also evaluated the expression levels of 12 selected ClDof genes under salt stress and ABA treatments using qRT-PCR. As a result, they showed differential expression under these treatments, suggesting their important roles in stress response. Taken together, our results provide a basis for future research on the biological functions of Dof genes in watermelon.

Comprehensive Analysis of TIFY Transcription Factors and Their Expression Profiles under Jasmonic Acid and Abiotic Stresses in Watermelon.

The TIFY gene family is plant-specific and encodes proteins involved in the regulation of multiple biological processes. Here, we identified 15 TIFY genes in the watermelon genome, which were divided into four subfamilies (eight JAZs, four ZMLs, two TIFYs, and one PPD) in the phylogenetic tree. The ClTIFY genes were unevenly located on eight chromosomes, and three segmental duplication events and one tandem duplication event were identified, suggesting that gene duplication plays a vital role in the expansion of the TIFY gene family in watermelon. Further analysis of the protein architectures, conserved domains, and gene structures provided additional clues for understanding the putative functions of the TIFY family members. Analysis of qRT-PCR and RNA-seq data revealed that the detected ClTIFY genes had preferential expression in specific tissues. qRT-PCR analysis revealed that nine selected TIFY genes were responsive to jasmonic acid (JA) and abiotic stresses including salt and drought. JA activated eight genes and suppressed one gene, among which ClJAZ1 and ClJAZ7 were the most significantly induced. Salt and drought stress activated nearly all the detected genes to different degrees. These results lay a foundation for further functional characterization of TIFY family genes in Citrullus lanatus.

The bZIP gene family in watermelon: genome-wide identification and expression analysis under cold stress and root-knot nematode infection.

The basic leucine zipper (bZIP) family transcription factors play crucial roles in regulating plant development and stress response. In this study, we identified 62 ClabZIP genes from watermelon genome, which were unevenly distributed across the 11 chromosomes. These ClabZIP proteins could be classified into 13 groups based on the phylogenetic relationships, and members in the same group showed similar compositions of conserved motifs and gene structures. Transcriptome analysis revealed that a number of ClabZIP genes have important roles in the melatonin (MT) induction of cold tolerance. In addition, some ClabZIP genes were induced or repressed under red light (RL) or root-knot nematode infection according to the transcriptome data, and the expression patterns of several ClabZIP genes were further verified by quantitative real-time PCR, revealing their possible roles in RL induction of watermelon defense against nematode infection. Our results provide new insights into the functions of different ClabZIP genes in watermelon and their roles in response to cold stress and nematode infection.