Background Elevated temperature and drought stress have substantial impacts on fruit quality, especially in terms of sugar metabolism and content. β-Amylase (BAM) plays a critical role in regulating jujube fruit sugar levels and abiotic stress response. Nevertheless, little is known about the regulatory functions of the BAM genes in jujube fruit. Results Nine jujube BAM genes were identified, clustered into four groups, and characterized to elucidate their structure, function, and distribution. Multiple sequence alignment and gene structure analysis showed that all ZjBAM genes contain Glu-186 and Glu-380 residues and are highly conserved. Phylogenetic and synteny analysis further indicated that the ZjBAM gene family is evolutionarily conserved and formed collinear pairs with the BAM genes of peach, apple, poplar, Arabidopsis thaliana, and cucumber. A single tandem gene pair was found within the ZjBAM gene family and is indicative of putative gene duplication events. We also explored the physicochemical properties, conserved motifs, and chromosomal and subcellular localization of ZjBAM genes as well as the interaction networks and 3D structures of ZjBAM proteins. A promoter cis-acting element analysis suggested that ZjBAM promoters comprise elements related to growth, development, phytohormones, and stress response. Furthermore, a metabolic pathways annotation analysis showed that ZjBAMs are significantly upregulated in the starch and sucrose metabolism, thereby controlling starch-maltose interconversion and hydrolyzing starch to maltose. Transcriptome and qRT-PCR analyses revealed that ZjBAMs respond positively to elevated temperature and drought stress. Specifically, ZjBAM1, ZjBAM2, ZjBAM5, and ZjBAM6 are significantly upregulated in response to severe drought. Bimolecular fluorescence complementation analysis demonstrated ZjBAM1-ZjAMY3, ZjBAM8-ZjDPE1, and ZjBAM7-ZjDPE1 protein interactions that were mainly present in the plasma membrane and nucleus. Conclusion The jujube BAM gene family exhibits high evolutionary conservation. The various expression patterns of ZjBAM gene family members indicate that they play key roles in jujube growth, development, and abiotic stress response. Additionally, ZjBAMs interact with α-amylase and glucanotransferase. Collectively, the present study provides novel insights into the structure, evolution, and functions of the jujube BAM gene family, thus laying a foundation for further exploration of ZjBAM functional mechanisms in response to elevated temperature and drought stress, while opening up avenues for the development of economic forests in arid areas.

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Anthocyanins are responsible for the intensity of color in plants; however, the systematic mechanisms underlying the color differences in the fruit of Ailanthus altissima remain unknown. Therefore, this study aims to analyze the transcriptomes of the white and red fruit of A. altissima by screening and validating the key genes involved in flavonoid and anthocyanin biosynthesis. Samples of A. altissima fruit were collected 30, 45, and 60 days after flowering, and their pigment and sugar content were determined. The anthocyanin content was significantly higher in red than in white fruits. Transcriptome analysis was also performed on the fruit samples, 73,807 unigenes were assembled and annotated to seven databases. Twenty‐one co‐expressed modules were identified via weighted gene co‐expression network analysis, of which two were associated with flavonoids and anthocyanins. Furthermore, in three growth stages, 126, 30, and 124 differentially expressed genes were screened between white and red fruit. Genes involved in flavonoid and anthocyanin metabolism were identified. AaDFR (A. altissima bifunctional dihydroflavonol 4‐reductase/flavanone 4‐reductase) and AaANS (A. altissima anthocyanidin synthase) were associated with flavonoid and anthocyanin metabolism. Members of the AaDFR and AaANS families were also identified, and their basic physicochemical characteristics, conserved domains, motif compositions, phylogenetics, and expression levels were analyzed. The overexpression of AaDFR and AaANS in transgenic Arabidopsis significantly increased the content of seed and foliar flavonoids and anthocyanins. The study elucidated the different mechanisms underlying fruit color development and provided insight into A. altissima plants breeding with commercially desirable properties.

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Forest-grass intercropping has great advantages in exploiting the potential of biological resources, improving the productivity of agriculture. Nevertheless, research on intercropping of ‘LingwuChangzao’ (Ziziphus jujuba Mill. cv. LingwuChangzao) with Gramineae herbage is less frequently reported. In this study, we measured the land equivalent ratio (LER), the nutritional quality of fruit and forage, and soil properties when ‘LingwuChangzao’ jujube was intercropped with Gramineae herbage compared to when grown in a corresponding monoculture, using clean tillage as a control. The results indicated that ‘LingwuChangzao’ jujube/Gramineae herbage intercropping significantly improved the LER in the system, the appearance traits, and the quality of jujube fruit (e.g., the total soluble solids, soluble sugar, vitamin C, anthocyanin, and flavonoids). Conversely, some nutritional quality indicators, such as dry matter, crude protein, crude fat, and neutral detergent fiber of forage, were lower than the corresponding monoculture. The physical properties in the soil improved with increased soil water content, electrical conductivity, total nitrogen, available phosphorus, etc. Further, intercropping systems had significant effects on soil organic carbon fractions and most of the C-N cycling enzyme activities. Redundancy analyses (RDA) revealed that electrical conductivity and total nitrogen were the dominant soil factors that influenced the C-N cycling enzyme activities and four soil organic carbon fractions correlated with C-N cycling soil enzyme activities. In conclusion, these results demonstrated that ‘LingwuChangzao’ jujube/Gramineae herbage intercropping significantly altered C-N cycling enzyme activities by driving the soil physicochemical properties and soil organic carbon fractions. Our findings show how to improve the productivity of ‘LingwuChangzao’ jujube and they provide insights into the mechanisms underlying healthy, biodiverse soils in agroecosystems.