GATA transcription factors are a class of transcriptional regulatory proteins that contain a characteristic type-IV zinc finger DNA-binding domain, which play important roles in plant growth and development. The GATA gene family has been characterized in various plant species. However, GATA family genes have not been identified in cucumber. In this study, 26 GATA family genes were identified in cucumber genome, whose physicochemical characteristics, chromosomal distributions, phylogenetic tree, gene structures conserved motifs, cis-regulatory elements in promoters, homologous gene pairs, downstream target genes were analyzed. Tissue expression profiles of cucumber GATA family genes exhibited that 17 GATA genes showed constitutive expression, and some GATA genes showed tissue-specific expression patterns. RNA-seq analysis of green and virescent leaves revealed that seven GATA genes might be involved in the chloroplast development and chlorophyll biosynthesis. Importantly, expression patterns analysis of GATA genes in response to abiotic and biotic stresses indicated that some GATA genes respond to either abiotic stress or biotic stress, some GATA genes such as Csa2G162660, Csa3G017200, Csa3G165640, Csa4G646060, Csa5G622830 and Csa6G312540 were simultaneously functional in resistance to abiotic and biotic stresses. Overall, this study will provide useful information for further analysis of the biological functions of GATA factors in cucumber.

Continuous watermelon cropping leads to increases in soil-borne diseases, which negatively affect plant growth. We investigated the impact of continuous watermelon cropping on soil biochemical properties, enzyme activities, microbial biomass, occurrence of Fusarium wilt, diversity and structure of bacterial and fungal communities, as well as the relationship among these factors with plant growth. The results showed significant decreases in soil pH, OM, AN, AP, and AK contents (p < 0.05), while UA, APA, and DA were reduced, along with declines in MBC and MBN in the rhizosphere soil of continuous watermelon cropping (p < 0.05). The population of FON and Fusarium wilt incidence increased significantly after continuous cropping (p < 0.05). High-throughput sequencing analysis revealed that the richness and diversity of soil bacterial and fungal communities significantly decreased (p < 0.05). There were significant differences in bacterial and fungal community composition between the continuous cropping and control groups. Besides, the Pearson correlation analysis of plant growth and environmental factors revealed that soil parameters, including pH, SOM, AN, AP, UA, APA, DA, MBC, and the richness and diversity of bacterial and fungal communities all had significant effects on plant growth. Additionally, the incidence of Fusarium wilt and the population of FON negatively affected growth. In conclusion, we hypothesize that soil acidification, deterioration of biochemical properties, an increase in Fusarium wilt, and changes in microbial community structure are causes of poor watermelon growth.

Dirigent proteins (DIR) play important roles in the biosynthesis of lignins and lignans, defensive responses, secondary metabolism, and disease resistance in plants. The DIR gene family has been identified and studied in many plants. However, the identification of DIR gene family in eggplant has not been conducted yet. Therefore, in this study, based on the available genome information of eggplant, the DIR family genes in eggplant were identified with bioinformatics methods. The expression pattern analyses of eggplant DIR family genes in different organs and stresses were also conducted to understand their biological functions. The results showed that a total of 24 DIR genes were identified in the eggplant, which were divided into three subfamilies (DIR-a, DIR-b/d, and DIR-e). Synteny analysis of DIR genes among eggplant, Arabidopsis, and rice showed that 15 eggplant DIR genes were colinear with 18 Arabidopsis DIR genes, and 16 eggplant DIR genes were colinear with 15 rice DIR genes. Phylogenetic tree analysis showed that 19 pairs of orthologous genes were identified between eggplant and pepper. The cis-acting elements analysis implied that the eggplant DIR genes contained a lot of cis-elements associated with stress and hormone response. The organ-specific expression analysis of eggplant DIR family genes revealed that only the SmDIR3 gene was highly expressed in all the 19 organs of eggplant. Some SmDIR genes, including SmDIR7, SmDIR8, SmDIR11, SmDIR14, SmDIR18, SmDIR19, SmDIR20, and SmDIR23, were not or were lowly expressed in the eggplant organs, while the other eggplant DIR family genes showed an organ-specific expression pattern. Furthermore, 19 of 24 SmDIR genes were differentially expressed in response to abiotic and biotic stresses. 5 SmDIR genes, including SmDIR3, SmDIR5, SmDIR6, SmDIR12, and SmDIR22, were differentially expressed under multiple types of abiotic and biotic stresses. Especially notable, the SmDIR22 gene was differentially expressed under three types of abiotic stresses and two types of biotic stresses, which indicated that the SmDIR22 gene plays an important role in the response to abiotic and biotic stresses. These results provide valuable evidence for a better understanding of the biological role of DIR genes in eggplant.

Introduction: Melatonin significantly enhances the tolerance of plants to biotic and abiotic stress, and plays an important role in plant resistance to salt stress. However, its role and molecular mechanisms in eggplant salt stress resistance have been rarely reported. In previous studies, we experimentally demonstrated that melatonin can enhance the salt stress resistance of eggplants.Methods: In this study, we treated salt-stressed eggplant plants with melatonin and a control treatment with water, then conducted physiological and biochemical tests, transcriptomic and metabolomic sequencing, and RT-qPCR validation at different stages after treatment.Results: The results showed that exogenous melatonin can alleviate the adverse effects of salt stress on plants by increasing the activity of antioxidant enzymes, reducing the content of reactive oxygen species in plants, and increasing the content of organic osmoprotectants. Transcriptomic and metabolomic data, as well as combined analysis, indicate that melatonin can activate the metabolic pathways of plant resistance to adverse stress. Compared to the control treatment with water, melatonin can activate the genes of the α-linolenic acid metabolism pathway and promote the accumulation of metabolites in this pathway, with significant effects observed 48 hours after treatment, and significantly activates the expression of genes such as SmePLA2, SmeLOXs and SmeOPR et al. and the accumulation of metabolites such as α-Linolenic acid, (9R,13R)-12-oxophytodienoic acid, 9(S)-HpOTrE and (+)-7-iso-Jasmonic acid. RT-qPCR validated the activating effect of melatonin on the candidate genes of the a-linolenic acid metabolism pathway.Discussion: This study analyzed the molecular mechanism of melatonin in alleviating eggplant salt stress, providing a theoretical foundation for the application of melatonin in enhancing eggplant salt stress resistance in production.

Gibberellic acid-stimulated in Arabidopsis (GASA), a unique small molecular protein of plants, plays an essential role in plant growth and development. The GASA family genes have been identified and studied in many plants. However, the identification of GASA gene family in Cucurbitaceae species has not been reported yet. Therefore, in this study, based on the available genome information on the Cucurbitaceae species, the GASA family genes in 10 Cucurbitaceae species including cucumber (Cucumis sativus), watermelon (Citrullus lanatus), melon (Cucumis melo), pumpkin (Cucurbita moschata), wax gourd (Benincasa hispida), sponge gourd (Luffa cylindrica), bottle gourd (Lagenaria siceraria), bitter gourd (Momordica charantia), chayote (Sechium edule), and snake gourd (Trichosanthes anguina) were identified with bioinformatics methods. To understand the molecular functions of GASA genes, the expression pattern analysis of cucumber GASA family genes in different tissues and stress responses were also analyzed. The results showed that a total of 114 GASA genes were identified in the 10 Cucurbitaceae species, which were divided into three subfamilies. Synteny analysis of GASA genes among cucumber, Arabidopsis and rice showed that nine cucumber GASA genes were colinear with 12 Arabidopsis GASA genes, and six cucumber GASA genes were colinear with six rice GASA genes. The cis-acting elements analysis implied that the cucumber GASA genes contained many cis-elements associated with stress and hormone response. Tissue-specific expression analysis of cucumber GASA family genes revealed that only the CsaV3_2G029490 gene was lowly or not expressed in all tissues, the CsaV3_3G041480 gene was highly expressed in all tissues, and the other seven GASA genes showed tissue-specific expression patterns. Furthermore, nine cucumber GASA family genes exhibited different degrees of regulatory response under GA, abiotic and biotic stresses. Two cucumber GASA genes, CsaV3_3G042060 and CsaV3_3G041480, were differentially expressed under multiple biotic and abiotic stresses, which indicated that these two GASA genes play important roles in the growth and development of cucumber.

Wheat intercropping in watermelon could provide relief from the occurrence of Fusarium wilting of watermelon, a severe soil-borne disease caused by the fungus Fusarium oxysporum f. sp. niveum (FON). The current study aims to investigate the effect of root exudates from three wheat cultivars and one watermelon cultivar on the growth of FON and the responses of Fusarium wilt in watermelon to intercropping with wheat. The results revealed the contrasting effects of root exudates on the mycelial growth of FON; the wheat root exudates inhibited the mycelial growth of FON, and watermelon root exudates promoted the mycelial growth of FON. Watermelon plants suffered less Fusarium wilt in the intercropping system than in the monocropping system. Wheat intercropping reduced the incidence of Fusarium wilt in watermelon, and this effect was associated with the role of wheat root exudates that inhibited the growth of FON. Malondialdehyde (MDA) contents decreased in the intercropping system compared with the monocropping system after FON inoculation. The catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), and polyphenol oxidase (PPO) activities, and total phenolics and flavonoid contents in the roots of watermelon in the intercropping system were significantly higher than those in the monocropping system. Real-time PCR analysis showed that ClCAT, ClSOD, ClAPX, and ClPPO defensive enzymes and ClPDF2.1 and ClPDF2.4 defensin-like gene expression were significantly induced during the early stage after FON inoculation in the intercropping system compared to the monocropping system, while peroxidases did not show a significant response to FON infection. It is suggested that intercropping with wheat alleviates Fusarium wilt of watermelon by reducing the population of FON in rhizospheric soil and activating physiological responses and defense gene expression to protect watermelon from FON infection and improve the resistance of watermelon to FON in the intercropping system.