Genomic-wide identification and expression analysis of AP2/ERF transcription factors in Zanthoxylum armatum reveals the candidate genes for the biosynthesis of terpenoids

Terpenoids are the main active components in the Zanthoxylum armatum leaves, which have extensive medicinal value. The Z. armatum leaf is the main by-product in the Z. armatum industry. However, the transcription factors involved in the biosynthesis of terpenoids are rarely reported. This study was performed to identify and classify the APETALA2/ethylene-responsive factor (AP2/ERF) gene family of Z. armatum. The chromosome distribution, gene structure, conserved motifs, and cis-acting elements of the promoter of the species were also comprehensively analyzed. A total of 214 ZaAP2/ERFs were identified. From the obtained transcriptome and terpenoid content data, four candidate ZaAP2/ERFs involved in the biosynthesis of terpenoids were selected via correlation and weighted gene co-expression network analysis. A phylogenetic tree was constructed using 13 AP2/ERFs related to the biosynthesis of terpenoids in other plants. ZaERF063 and ZaERF166 showed close evolutionary relationships with the ERFs in other plant species and shared a high AP2-domain sequence similarity with the two closest AP2/ERF proteins, namelySmERF8 from Salvia miltiorrhiza and AaERF4 from Artemisia annua. Further investigation into the effects of methyl jasmonate (MeJA) treatment on the content of terpenoids in Z. armatum leaves revealed that MeJA significantly induced the upregulation of ZaERF166 and led to a significant increase in the terpenoids content in Z. armatum leaves, indicating that ZaERF166 might be involved in the accumulation of terpenoids of Z. armatum. Results will be beneficial for the functional characterization of AP2/ERFs in Z. armatum and establishment of the theoretical foundation to increase the production of terpenoids via the manipulation of the regulatory elements and strengthen the development and utilization of Z. armatum leaves.

Optimization of the pulsed vacuum drying process of green walnut husk through temperature adaptive regulation

This study aimed to optimize the temperature adaptive conditions of pulsed vacuum drying (PVD) for green walnut husk (GWH) to tackle the issues of severe environmental pollution and limited utilization of GWH. The results of the single-factor experiment revealed that the optimal drying temperature for PVD of GWH was 65°C, with a pulsed ratio of 9 min: 3 min. The drying time decreased from 10.87 to 6.32 h with increasing drying temperature and from 8.83 to 6.23 kW·h/kg with increasing pulsed ratio. Energy consumption also decreased with shorter drying time and shorter vacuum time. Under this optimal variable temperature drying condition, GWH exhibited the highest total active substance content, with respective values of 9.43 mg/g for total triterpenes, 35.68 mg/g for flavonoids, 9.51 mg/g for polyphenols, and 9.55 mg/g for quinones. The experimental drying data of GWH were best fitted by a logarithmic model, with R2 values ranging from 0.9927 to 0.9943. Furthermore, the observed microstructure of GWH corresponded to the variations in total active substance content. This study provided valuable theoretical guidance for addressing environmental pollution associated with GWH and facilitating the industrialization and refinement of GWH drying processes. PRACTICAL APPLICATION: There is a growing interest in harnessing the potential value of agricultural waste to transform low-cost raw materials into high-value products while mitigating environmental pollution. In this study, for the first time, the effects of variable temperature pulsed vacuum drying on the content of active substances, drying time, and energy consumption of green walnut husk (GWH) were investigated. The findings serve as a theoretical foundation for addressing environmental pollution issues associated with GWH and enabling the industrialization and precision drying of GWH.