## 1 Introduction
Transcriptome sequencing, a high-throughput DNA sequencing technology, enables the rapid identification of DEGs and the elucidation of physiological processes or molecular mechanisms [28; 29]. It also represents a powerful means for analyzing gene expression, predicting gene function, and screening regulatory factors [29; 30]. For instance, in _Dendrobium candidum_, transcriptome sequencing was used to elucidate the genes involved in secondary metabolite biosynthesis. Similarly, in _Artemisia annua_, the mechanisms involved in jasmonic acid-induced artemisinin synthesis were deciphered through an integrated transcriptomic analysis. The expression profiles of genes in _Vitis viunifera_,Fagopyrum tataricum, Camellia sinensis, and _Setaria italica_ were also analyzed using transcriptome data, offering valuable insights into the regulation of secondary metabolism [31; 32; 33; 34]. However, the regulatory mechanisms governing terpene biosynthesis in _L. cubeba_ fruits under photoperiod variations remain uncharacterized, which limits the utilization of _L. cubeba_ fruit. _Litsea cubba_ (Lour.) Pers. (family: Lauraceae), commonly known as mountain pepper, is recognized as a significant specialty forest tree in China owing to its high essential oil content in roots, stems, leaves, flowers, and fruits [35; 36]. The fruit developmental stages of _L. cubeba_ are categorized into two distinct phases: the rapid essential oil accumulation phase in mid-July, and the seed maturation phase in September [35; 37]. Since the essential oil content in _L. cubeba_ fruits is significantly higher than in other plant organs, the essential oil is typically extracted from the fruits. _L. cubeba_ essential oil (LCEO) contains abundant terpenoids, particularly monoterponids (>90% of the total terpenoid content), including \(\alpha\)-pinene, \(\beta\)-pinene, camphene, D-limonene, linalool, and citral. These compounds possess notable biological properties, such as antimicrobial, anti-inflammatory, antioxidant, insecticidal, and mosquito-repellent activities [11; 38; 39]. _L. cubeba_ is a primary source of natural fragrances for the perfume and cosmetic industries. The essential oil can also substitute synthetic chemical preservatives to extend food shelf life. Besides its traditional use as a medicinal plant, _L. cubeba_ exhibits diverse therapeutic applications. For instance, mature fruits serve as analgesic agents, decocted roots alleviate rheumatic arthralgia, crushed leaves reduce swelling when applied topically, and fruit residue serves as a natural antibiotic feed additive [40]. Recent studies have further shown that the essential oil of _L. cubeba_ has therapeutic potential in the regulation of inflammation and the amelioration of intestinal health [41; 42]. Three methods are commonly employed for the extraction of the essential oil of _L. cubeba_--traditional pressing, solvent extraction, and ultrasonic-assisted extraction--with the last method resulting in the highest oil yield [40; 43]. With the completion of the high-quality genome assembly, _L. cubeba_ was confirmed to have a diploid genome (2\(n\) = 24), and 31,329 protein-coding genes were identified, which were unevenly distributed across its 24 chromosomes [11]. Additionally, [PERSON] (2020) et al. sequenced the transcriptomes of various _L. cubeba_ tissues (roots, leaves, and flowers), as well as fruits at different developmental stages [44]. The research on the terpenoid synthesis of _L. cubeba_ is mainly based on the analysis of the function of a single key gene, including the functional characterization of _L.cTPS42_ and _L.cTPS32_, as well as identifying transcription factors (_L.cMYC2_, _L.cERF19_, _L.cWRKY17_, and _L.cMYB106_), which promotes the understanding of the regulation of terpenoid biosynthesis [45; 46; 47; 48]. These studies provide a foundational basis for understanding the molecular mechanisms of terpenoid synthesis in _L. cubeba_. However, how environmental factors (such as light) affect the terpenoid synthesis of _L.