Patulin, a mycotoxin commonly found in fruits and derived products, causes serious health problems for humans and animals worldwide. Several microbial strains have been observed to possess the ability to effectively remove patulin. However, these methods are presently associated with disadvantages such as low degradation efficiency and an unclear biodegradation mechanism. In the current study, the characteristics of patulin degradation via Aspergillus niger FS10 were evaluated, and the mechanisms involved were analyzed using metabolomics technologies. The results showed that the suspension of A. niger FS10 could degrade 94.72% of patulin within 36 h. The moment concentration pf patulin was 0.116 μg/mL, and the detection limit value was 0.01 μg/mL. In addition, the patulin content was reduced to levels below the detection limit within 48 h. A. niger FS10 mainly degrades patulin by producing intracellular enzymes, which can convert patulin into ascladiol. This degradation method can effectively reduce the damage caused by patulin to HepG2 cells. In addition, the patulin treatment significantly affects the pentose phosphate pathway and the glutathione pathway. These two metabolic pathways are speculated to be closely related to patulin degradation via A. niger FS10. The incubation of A. niger FS10 with patulin-contaminated apple pomace can not only eliminate patulin but also increase the utilization of apple pomace. Therefore, our research results provide a new method for addressing patulin contamination in the food and feed industries.

Calcineurin B-like (CBL) proteins are plant-specific calcium sensors critical for ion homeostasis and stress tolerance. Here, seven MdCBL genes were genome-wide identified in apple (Malus domestica). We conducted systematic bioinformatic profiling of their physicochemical features, subcellular localization, cis-regulatory elements, phylogeny, secondary structures, phosphorylation sites, and functional annotations and further verified the salt-stress regulatory function of MdCBL5 via transgenic tests. MdCBL proteins contain 210–246 amino acids, with molecular weights of 24,196.73–28,283.39 Da, pI values of 4.63–4.97 and instability indices of 37.12–49.20. Localization prediction placed these proteins in nuclei, cytosol and chloroplasts. Their promoter regions are rich in hormone-responsive (auxin, ABA, salicylic acid) and stress-responsive (cold, drought, salt) cis-elements. Phylogenetic clustering divided MdCBLs into five subgroups (A–E) with high homology to Arabidopsis CBLs. Random coils and α-helices dominate their secondary structures, and serine residues constitute most phosphorylation sites. Functional annotation supports their involvement in calcium signaling, ion transport and diverse stress adaptation. Salt stress experiments have confirmed that MdCBL5 may enhance apple salt resistance by promoting MdSOS gene expression. Meanwhile, transient transformation in apple fruit showed that MdCBL5 can effectively enhance fruit quality traits. Collectively, this study establishes a theoretical foundation for further elucidating the biological functions of the apple MdCBL5 gene and provides valuable insights for genetically improving stress resistance and fruit quality in apple via molecular breeding strategies.

Nitrogen assimilation is vital for apple growth, yield, and quality, with nitrate reductase (NIA), nitrite reductase (NIR), glutamine synthetase (GS), and glutamate synthase (GOGAT) serving as key regulatory enzymes. This study systematically identified these four gene families in apple (Malus domestica) through genome-wide analysis and examined their expression patterns under nitrate treatment. In total, 13 genes were identified, 2 MdNIAs, 1 MdNIR, 7 MdGSs, and 3 MdGOGATs, with gene lengths ranging from 2577 to 27736 base pairs (bp); MdGLT1A had the longest coding sequence (6627 bp). The encoded proteins contained 355–2208 amino acids, with predicted isoelectric points (pIs) between 5.55 and 6.63. Subcellular localization analysis predicted distinct compartmentalization: MdNIA1A in peroxisomes; MdGS1 in the cytosol; MdNIR1, MdGS2, and MdGLU1 in chloroplasts; and MdGLT1 in mitochondria/chloroplasts. Functional site prediction revealed multiple phosphorylation and glycosylation sites, with ATP/GTP-binding motifs present only in certain MdGOGAT proteins. Protein interaction analysis suggested close associations among these genes and possible interactions with NRT2.1/2.2. Chromosomal mapping showed their distribution across eight chromosomes, while promoter analysis identified diverse cis-acting regulatory elements (e.g., ABRE and G-box). Under nitrate treatment (0–12 h), these genes exhibited distinct expression dynamics: MdNIA1A and B were rapidly induced (0–6 h) and maintained high expression; MdNIR1 peaked at 6 h and then declined; MdGS1.1B was activated after 6 h; and MdGS2A, MdGLU1, and MdGLT1A/B peaked at 6 h before decreasing. Therefore, these results elucidate the structural and functional divergence of nitrogen assimilation genes in apple and provide a basis for understanding nitrogen utilization mechanisms and developing nitrogen-efficient breeding strategies.