Fleshy fruit ripening is a unique biological process that involves dramatic changes in a diverse array of cellular metabolisms. The regulation of these metabolisms is essentially mediated by cellular signal transduction of internal (e.g., hormones) and external cues (i.e., environmental stimuli). Mitogen-activated protein kinase (MAPK) signaling pathways play crucial roles in a diverse array of biological processes, such as plant growth, development and biotic/abiotic responses. Accumulating evidence suggests that MAPK signaling pathways are also implicated in fruit ripening and quality formation. However, while MAPK signaling has been extensively reviewed in Arabidopsis and some crop plants, the comprehensive picture of how MAPK signaling regulates fruit ripening and quality formation remains unclear. In this review, we summarize and discuss research in this area. We first summarize recent studies on the expression patterns of related kinase members in relation to fruit development and ripening and then summarize and discuss the crucial evidence of the involvement of MAPK signaling in fruit ripening and quality formation. Finally, we propose several perspectives, highlighting the research matters and questions that should be afforded particular attention in future studies.

Jujube (Ziziphus jujuba Mill.) is a fruit crop of high economic value, renowned for its distinctive flavor and wide range of phenotypic diversity. Despite major advancements in jujube genomics, the role of genetic variants in underlying agronomic trait formation is still poorly understood. Here, we used seven high-quality jujube genomes to construct a pan-TE (transposon element) map and investigated how TEs shape genome evolution and agronomic traits. We found that TEs constitute 29.05%–30.38% of the genome, predominantly long terminal repeat (LTR) retrotransposons such as Copia and Gypsy. A positive correlation (R2 = 0.76) between TE content and genome size underscores their role in genomic expansion. TE insertions within gene bodies significantly reduce gene expression, particularly for genes involved in cell wall biosynthesis and glucose metabolism. Population scale analysis of 1041 accessions identified 4176 transposable element insertion polymorphisms (TIPs) that distinguish wild and cultivated groups. Wild jujubes harbor stress-related TIPs (e.g. in peroxidase genes), whereas cultivated accessions carry TIPs linked to fruit development. Notably, a Gypsy insertion upstream of the cellulose synthase gene ZjCESA4 is associated with reduced expression and thinner pericarp in ‘Dongzao’ compared to ‘Huizao’. Similarly, a downstream LTR/Gypsy insertion near the MADS-box transcription factor gene ZjAGL18 correlates with suppressed expression, highlighting the recurrent targeting of key regulatory genes by TEs during domestication. Our findings demonstrate that TIPs are a major source of genetic variation in jujube, providing molecular markers for breeding programs that aim to balance fruit quality and stress resilience.

Aiming at the problems of tree vigor decline and unstable fruit quality caused by soil impoverishment and easy nutrient loss in the Ziziphus jujuba Mill. ‘Huizao’ (Huizao) producing areas of southern Xinjiang, the application effect of bag-controlled slow-release fertilizer (BCSRF) in this region remains unclear. In this study, a field experiment was conducted with four fertilization concentration gradients, including CK (0 kg/ha), T1 (22 kg/ha), T2 (44 kg/ha), and T3 (66 kg/ha), to investigate the effects of BCSRF on soil nutrient dynamics and plant growth, as well as the fruit yield and quality of Huizao. The results showed that BCSRF could effectively maintain the supply levels of soil alkali-hydrolysable nitrogen, available phosphorus, and available potassium during key growth periods, among which the T3 treatment exhibited the most significant effect. This treatment not only significantly increased the yield per plant of Huizao by 39.34% compared with the control, but also markedly enhanced the contents of the endogenous substance, including soluble sugar and cyclic adenosine monophosphate. This study confirms that under the condition of sandy loam soil in southern Xinjiang, a single basal application of an appropriate amount of BCSRF can achieve continuous nutrient supply, simultaneously improve soil fertility and fruit quality, providing a theoretical basis and technical guidance for simplified and efficient fertilization in local jujube orchards.

As calcium responders, calcium dependent protein kinases (CDPKs) play an important role in plant growth and development and in response to biotic and abiotic stresses. However, information on CDPKs in jujube (Ziziphus jujuba Mill.) (ZjCDPKs) is limited. In the current study, a total of 21 ZjCDPKs were identified, which are located on eight chromosomes. Gene structure and conserved motif analysis showed that all ZjCDPKs have similar gene structures and conserved motifs, except for ZjCDPK9 and ZjCDPK21. The CDPKs from Arabidopsis, rice, tomato, alfalfa, and jujube were divided into eight subgroups, and the members of ZjCDPKs were unevenly distributed across these subgroups. Colinear analysis revealed that 12 homozygous CDPKs were detected between jujube and Arabidopsis, and 14 pairs were found between jujube and tomato. Additionally, four types of cis-acting elements were identified in the promoters of the ZjCDPKs, including hormone, stress, development, and light response elements. The expression profiles of ZjCDPKs at different fruit growth stages, in response to phytoplasma infection, cold, and salt stresses revealed that most ZjCDPKs were either up- or down-regulated. Finally, varying numbers of transcription factors were observed to interact with the promoter region of ZjCDPK4/6/7/8/10/14/16 and showed opposite expression patterns in response to cold or salt stress. The systematic analysis of ZjCDPKs provides important information for further functional characterization of CDPKs in jujube in response to multiple biological processes.