Identification of LiMYC and LiTPS Gene Families Involved in MeJA-Induced Terpene Accumulation in Lagerstroemia indica ‘Whit III’

Methyl jasmonate (MeJA) is a key regulator of plant defense and abiotic stress responses, while terpenoids are important secondary metabolites. However, the effects of MeJA on floral volatiles in Lagerstroemia indica and the underlying mechanisms remain unclear. In L. indica ‘Whit III’, MeJA treatment rapidly increased the emission of monoterpenes (e.g., citronellol) and sesquiterpenes (e.g., trans-farnesol) and advanced the peak emission time. We identified 34 LiTPS and 22 LiMYC genes in the genome, with promoter regions enriched in JA-responsive cis-elements. Expression analysis showed that LiMYC genes encoding putative JA repressors were transiently upregulated, whereas LiTPS genes located in a chromosome 11 cluster and LiTPS13 (7.33-fold induction) were strongly activated. These results suggest that MeJA may promote an early scent production through the coordinated activation of specific LiMYC and LiTPS gene sets, pointing to a potential mechanism by which jasmonate signaling modulates floral volatile emission.