# Lavandula Species, Their Bioactive Phytochemicals, and Their Biosynthetic Regulation
## 5 Biosynthesis Regulation of Lavelender Bioactive Phytochemicals
### Gene-Based Regulation of Lamiaceae Species Secondary Metabolites
\(\times\) intermediia_[91; 92; 93; 94; 95; 96; 97]; limonene synthase (_LIMS_), linalool synthase (_LINS_), trans-alpha-bergamotene synthase (_BERS_), bornyl diphosphate synthase (_BPPS_), \(\beta\)-phellandrene synthase (_BPHS_), and acyltransferase-1/2 (_AT1/2_) were identified in _L. angustifolia_[98; 99; 99; 98] and fenchol synthase (_FENS_), \(\alpha\)-pinene synthase (_PINS_), and germacrene A synthase (_GEAS_) in _L. pedunculata_ Mill. [100]. The EST technique, however, has proven to be insufficient in identifying nonabundant transcripts and in recent years has been replaced by more comprehensive and cost-effective sequencing methods that allow for the analysis of the entire transcriptome, rather than just a small portion, and provide more detailed and accurate information about gene expression levels and patterns [73; 97; 101]. Genome and transcriptome sequencing data provide unprecedented insight into the genetic basis of lavender. Published in 2018, the first draft genome of _L. angustifolia_ (cv. Maillette), with a total length of 870 Mbp [67], revealed 62,141 protein-coding genes and 2003 noncoding genes (tRNA/rRNA). The latter reported the chromosome-level genome of _L. angustifolia_ (cv. Jingxun 2), consisting of 894.5 Mbp anchored to 27 chromosomes. This genome assembly revealed 65,905 protein-coding sequences, of which 62,822 (95.3%) had annotated homologs in the database. The number of noncoding RNAs was estimated to be 1351 miRNAs, 1298 tRNAs, 1199 snRNAs, and 399 rRNAs [68]. Both genome assemblies have a GC content of approximately 38%. A significant difference was observed between the assemblies of the two cultivars in the density of repetitive sequences. In the case of the Maillette cultivar, it was estimated that 43% of the genome consists of repetitive sequences, while a higher proportion of 58% was reported for the Jingxun 2 cultivar. Similar to other species, LTR retrotransposons are the most prevalent type of repeated sequences in lavender [67; 68]. Evaluation using benchmarking universal single-copy orthologues (BUSCO) indicated a high degree of completeness of both published assemblies. The first draft genome revealed sequences for all known genes involved in MEP and MVA pathways, most of them present in more copies. Genes for the enzymes catalyzing the first and last step of the MEP pathway, _DXS_, and _HDR_, were present in 13 and 7 copies, respectively. When compared to genomes of _Mentha longifolia_ ([PERSON], _Arabidopsis thaliana_ ([PERSON], _Zea mays_ (L.), and _Oryza sativa_ (L.), the highest copy number of the genes involved in terpenoid biosynthesis was observed in lavender [67]. A high copy number of these genes in the genome of lavender demonstrates a high degree of optimization for EO production. _TPS_ genes can be grouped into seven subfamilies [102]. In lavender, five of these subfamilies were found to be present and, overall, 100 genes for TPS were identified. The _TPS-b_ subfamily, which typically encodes monoterpene synthases, was the most expanded one in lavender and genes belonging to this subfamily showed high levels of expression in the glandular trichomes of _L. angustifolia_[67].