Transcriptional regulation of monoterpenoid indole alkaloid biosynthesis in Catharanthus roseus

Catharanthus roseus (Madagascar periwinkle) produces valuable monoterpenoid indole alkaloids (MIAs) such as vincristine and vinblastine, crucial for cancer treatment. MIA extraction is costly due to their rarity and complex structure. Jasmonates (JAs) regulate MIA production by inducing biosynthesis genes and influencing precursors formation. The transcription factors (TFs) ORCA2 and ORCA3 are key regulators of MIA genes, activated by CrMYC2, which itself is repressed by JAZ proteins in the absence of JA-Ile.<br>The study aimed to understand TF regulation of the MIA pathway. Overexpression of a derepressed CrMYC2 mutant (CrMYC2D126N) was unsuccessful due to its toxicity and system limitations. Protein interaction studies revealed the F-box protein O2.51 interacts with ORCA2, inhibiting its activity, possibly by targeting it for degradation. Casein kinase I proteins (CKIs) were also identified as ORCA3 interactors, phosphorylating ORCAs and inhibiting their activity. The CKIs localize in the nucleus, supporting their role in TF regulation.<br>Results suggest ORCA activity is inhibited through phosphorylation by CKI, potentially enhancing degradation when combined with O2.51. These findings highlight the complexity of regulating TF activity and propose strategies like CKI gene knockout or using non-phosphorylatable ORCAs to enhance MIA production.<br>