## 3 Discussion
### Phytohormone Regulation of Cannabinoid Biosynthesis
Neither of them changed in abundance in response to ABA or BA, respectively (Supplementary Figure S5), indicating that GT disc cells are likely relatively insensitive to these phytohormones, as seen by the small number of DAPs caused by ABA and BA (Figure 2). In arabidopsis [21] and conserved in other species [24], trichome initiation is centrally controlled by the MBW complex where complex developmental, stress, and phytohormonal signals are integrated through it [21], which include the KIN, JA, and SA signalling pathways [22]. Together, the magnitude of impact (Figure 2) and similarity in responses (Figures 4 and 5) suggest that KIN, SA, and JA may have important roles in regulating cannabis trichome development, morphology, and/or productivity by regulating many of the same biological processes (Figure 3). When examined in detail, seven DAPs that were affected by either KIN, SA, and/or JA point to these phytohormones' involvement in trichome differentiation and morphogenesis processes (Figure 5C-I). These included CER10, CER2, and LACS9 that are involved in very-long-chain fatty acid (VLCFA) elongation for cuticular wax synthesis, as well as cpSecA, TC214, and WTF1, which are involved in plastidial function and development. Also important was ACLA-1, which is involved in cytosolic acetyl-CoA synthesis. CER10 is an enoyl-CoA reductase involved in VLCFA elongation that is required for cuticular wax synthesis. It has been shown to have a conserved role in trichome development in both tomato and arabidopsis [63], and knockout mutants resulted in reduced trichome densities. Cannabis GTs have prolonged development that spans flower development [2] and involves remodelling of the cell wall and cuticle thickening of the apical surface of disc cells to create the storage cavity [64]. Not only did we see CER10 increasing when mature GTs were treated with either KIN, JA, or SA (known to positively regulate trichome initiation across species), but it also decreased in the 24 h vs. 0 h controls when no exogenous hormones were present (Supplementary Figure S3). This would suggest that CER10 has a role in regulating GT differentiation that would be likely linked to cell wall synthesis and storage cavity formation. This further implies that constant rates of JA, SA, or KIN may be needed to maintain GT homeostasis. Changes in CER2 and LACS9 abundance by KIN, SA, and JA further substantiate their roles in directing cuticular wax formation in GTs (Figure 5H-I). CER2 is required for the fatty acid elongase complex to synthesise VLCFAs of lengths greater than 28 carbons [65]. We observed that the three phytohormones caused CER2 abundance to decrease by an average of 83%, indicating that GT cuticular wax composition would be shifted, possibly to shorter-chain-length VLFCAs, by these phytohormones. This parallels what is seen in arabidopsis trichomes which have an altered cuticular wax composition and is attributable to altered expression of the cuticular wax pathway that includes low expression of _CER2_[66; 67]. LACS are a family of long-chain acyl-CoA synthetases that catalyse free fatty acids into fatty acyl-CoAs and are involved in fatty acid transport in the cell [68; 69]. In arabidopsis, LACS9 is responsible for 90% of LACS activity in leaf plastids [70], thus having it decrease by KIN and SA may indicate to a shift in fatty acid allocation in cannabis GT metabolism. Increased abundances of plasidial proteins cpSecA, TIC214, and WTF1 by KIN, SA, and JA suggests roles in regulating GT leucoplast function (Figure 5C-E). CpSecA is a translocation ATPase and part of the chloroplast secretory (cpSec) pathway [71]. The cpSec pathway is responsible for the transport of unfolded proteins into the chloroplast lumen and is essential for the development and differentiation of chloroplasts and all other plastid types [72; 73]. Proper functioning of this pathway is essential for trichome development, as ATcpSecA-deficient mutants result in malformed arabidopsis trichomes [71].