## 4 Discussion  
In the present study, we provide evidence that the _tps1_ gene in _T. atroviride_ HB20111 is associated with the biosynthesis of sesquiterpenoids. Our results also suggest that the _tps1_ gene directly or indirectly affects the expression of genes involved in other secondary metabolite biosynthetic pathways. The deletion of _tps1_ almost eliminated the production of terpinolene, farnesylacetone, \(\beta\)-cedrene, \(\beta\)-phellandrene, \(\alpha\)-angelica lactone, and acorenone b in _T. atroviride_ (Table S2). This finding is consistent with previous studies showing that the deletion of terpene synthase reduces terpene production [(39; 40)]. Previous studies have elucidated various functions of these terpen. For instance, terpinolene has demonstrated inhibitory effects on acetylcholinesterase-incetase (AChE) expression and the suppression of gray mold mycelium growth [(41; 42; 43)]; the application of farnesyl acetone results in a significant reduction in the individual development observed in the little cabbage moths (_P. xylostella_) [(44)]; \(\beta\)-cedrene possesses natural diuretic and anti-inflammatory properties, which may aid in cellulite improvement [(45)]; \(\beta\)-phellandrene acts as an insect sex pheromone, disrupting insect behavior [(46)]; \(\alpha\)-angelica lactone inhibits mouse tumor growth induced by benzopyrene in mice [(47)]; and pure acorenone b exhibits inhibitory activity against both acetylcholinesterase-incetase (AChE) and butyrylcholinesteraseerase (ChE), showing potential for the treatment of [PERSON]'s disease [(48)]. These experimental findings provide valuable insights into the biological functions of terpenoids within _T. atroviride_ HB20111. Moreover, deletion of the _tps1_ gene resulted in significant changes in terpenoid species and content, which significantly affected the antifungal activity of _T. atroviride_ HB20111 against _Colletotrichum siamense_, _Fusarium pseudograminearum_, and _Fusarium oxysporum_ f.spc Cucumerium. This is in line with previous findings that plants such as cotton (_Gossypium_ species) and Camphor cinnamon may produce fewer antimicrobial terpenoids in the absence of certain terpene synthase genes, thus weakening their defense mechanisms against fungal pathogens [(49; 50; 51)]. The main reason for this is that, when terpene synthase genes are disrupted or missing, this leads to a reduction in the biomass of specific terpenoids or the production of different and sometimes less-effective compounds. In addition, the  
Figure 8: Effects of 20111 and its mutant on chlorophyll and soluble sugar content in wheat under 28 \({}^{\circ}\)C light condition. terpenes encoded by the _tps1_ gene are believed to play a crucial role in promoting plant growth through enhancing root system development. Further scientific investigations are required to clarify the underlying molecular mechanism. Furthermore, we hypothesize that the antifungal efficacy of _T. atroviride_'s VOCs may be attributed to the biosynthesis of two or more structurally distinct secondary metabolites. The cessation of one metabolite's production does not compromise antifungal activity, as the synthesis of other metabolites compensates for the deficiency. This study also conducted a comparative analysis of terpene metabolites among wild-type, deletion strains, and overexpression strains, revealing significant variation in the terpene profiles across the different strains. The _tps1_-deleted mutants exhibited a marked reduction in or absence of most sesquiterpene VOCs, confirming the potential involvement of the _tps1_ gene in sesquiterpene compound biosynthesis. Additionally, both the deletion and overexpression strains yielded novel terpene metabolites; however, not all volatile organic compounds were detected in both strains, particularly nerolidol, \(\beta\)-acenenol, and guaiene, which were exclusively produced by the _Otps1_ strain. A previous study by [PERSON] et al.