Locoweeds, including Oxytropis and Astragalus species, are globally recognized as plants containing swainsonine (SW), a neurotoxic alkaloid that induces neurological dysfunction and growth inhibition in livestock. SW is produced by endophytic fungi in plants; the pyrroline-5-carboxylate reductase (P5CR) gene is critical in the fungal SW biosynthetic pathway. In this study, a P5CR gene knockout mutant (ΔP5CR) was constructed from the endophytic fungus Alternaria oxytropis OW7.8 isolated from Oxytropis glabra. Compared to the wild-type strain (A. oxytropis OW7.8), the SW content in the ΔP5CR mycelia was significantly reduced, indicating that the P5CR gene plays a crucial role in promoting SW biosynthesis. Compared to the wild-type strain A. oxytropis OW7.8, the ΔP5CR mutant exhibited distinct morphological alterations in both colony and mycelial structures. The transcriptomic analysis of A. oxytropis OW7.8 and ΔP5CR revealed the downregulation of six genes associated with SW biosynthesis. Metabolomic profiling further demonstrated altered levels of six metabolites linked to SW synthesis. These findings provide foundational insights into the molecular mechanisms and metabolic pathways underlying SW biosynthesis in fungi. They hold significant value for future strategies to control SW in Oxytropis glabra and contribute positively to the protection and sustainable development of grassland ecosystems.

Melon (Cucumis melo L.) is an important horticultural crop worldwide. Ethylene regulates the ripening process and affects the ripening rate. To screen genes that are differentially expressed at the burst of ethylene climacteric in melon fruit, we performed suppression subtractive hybridization (SSH) to generate forward and reverse libraries, for which we sequenced 439 and 445 clones, respectively. Our BLAST analysis showed that the genes from the 2 libraries were involved in metabolism, signal transduction, cell structure, transcription, translation, and defense. Six genes were analyzed by qRT-PCR during the differential developmental stage of melon fruit. Our results provide new insight into the understanding of climacteric ripening of melon fruit.

Auxin efflux carrier protein PIN (PIN-FORMED) can regulate the polar transport of auxin in plants, which plays an important role in plant growth, development, and environmental adaptation. This study conducted a comprehensive analysis using bioinformatics, RT-qPCR, and transcriptome data to systematically identify the CmPINs and investigate their expression patterns and functions. A total of 15 PIN genes were identified in the melon genome, distributed unevenly across chromosomes. Only one pair of segmental duplications was found, indicating a relatively independent evolution of melon auxin efflux carriers. The promoter regions contain various hormone- and environment-responsive elements. Organ-specific expression analysis showed that CmPIN1, CmPIN13 and CmPIN15 were highly expressed in fruits, CmPIN2, CmPIN8, and CmPIN12 in leaves, and CmPIN1, CmPIN4, CmPIN5, and CmPIN8 in roots respectively. CmPIN15, localized to the plasma membrane, encodes 417 amino acids. Under hormone treatment in young leaves, CmPINs showed differential expression. GO and KEGG analyses of interacting proteins revealed their involvement mainly in the auxin-activated signaling pathway, response to organic substances, and photosynthetic carbon fixation. This study provides a foundation for further elucidating the biological functions of the PIN gene family in melon.

Chitinase is a key enzyme involved in insect chitin metabolism, and RNA interference (RNAi) targeting the corresponding gene represents a promising strategy for eco-friendly pest management. However, the design parameters of double-stranded RNA (dsRNA), particularly fragment length and target position, remain insufficiently optimized. To investigate the effects of these parameters on the RNAi efficiency against the MsChi2 gene in Mythimna separata, we synthesized four dsRNAs of 60, 200, 500, and 1000 bp and administered them to larvae. The results indicated that 200 and 500 bp dsRNAs significantly inhibited larval growth, reduced survival, and silenced MsChi2 expression. Among these, the 200 bp dsRNA exhibited the most pronounced effects, including a 59% inhibition rate of larval body weight, 65.9% mortality, and 62% target gene silencing efficiency, accompanied by a significant reduction in chitin content and abnormalities in molting and pupation. Using 200 bp as the optimal length, five fragments targeting different coding regions of the gene were evaluated. All except one exhibited strong activity, and their RNAi efficiencies were positively correlated with the predicted numbers of effective small interfering RNAs. Collectively, these findings demonstrate that dsRNA length and target position jointly modulate RNAi efficiency, with 200 bp representing the optimal fragment length. This study provides a rational design framework for dsRNA development and establishes both theoretical and practical foundations for RNAi-based management of M. separata.