CsMIKC1regulates inflorescence development and grain production in Cannabis sativaplants

Female inflorescence is the primary output of medical Cannabis. It contains hundreds of cannabinoids that accumulate in the glandular trichomes. However, little is known about the genetic mechanisms governing Cannabisinflorescence development. In this study, we reported the map-based cloning of a gene determining the number of inflorescences per branch. We named this gene CsMIKC1since it encodes a transcription factor that belongs to the MIKC-type MADS subfamily. Constitutive overexpression of CsMIKC1increases inflorescence number per branch, thereby promoting flower production as well as grain yield in transgenic Cannabisplants. We further identified a plant-specific transcription factor, CsBPC2, promoting the expression of CsMIKC1. CsBPC2mutants and CsMIKC1mutants were successfully created using the CRISPR-Cas9 system; they exhibited similar inflorescence degeneration and grain reduction. We also validated the interaction of CsMIKC1 with CsVIP3, which suppressed expression of four inflorescence development-related genes in Cannabis. Our findings establish important roles for CsMIKC1in Cannabis, which could represent a previously unrecognized mechanism of inflorescence development regulated by ethylene.