Mapping and Examination of a Quantitative Trait Locus Controlling Trichome Abundance in Brassica napus

A gene encoding a novel, R3 single-repeat, MYB protein related to the trichome repressor TRIPTYCHON was identified within the shared region and designated TRIPTYCHON-LIKE (TRL). DOS-2 harbors a single BnTRL gene, whereas NAM-0 contains four tandemly-linked copies, although BnTRL transcript abundance did not correlate directly with trichome density. The expanded TRL gene family is unique to the Brassicaceae and BnTRL proteins physically interact with the GL1-binding domain of GL3, a core component of the GL1–GL3–TTG1 trichome initiation complex.

Analysis of additional genes within the shared QTL region or absent in DOS-2 revealed regulators associated with chromatin modification (e.g. ADA2b, RBBP6-like), hormone signaling (ARR2, GH3, JAM3, HAT4), cytoskeletal dynamics (SPIRAL2, MAP65-2, MAP70-5, SPIKE1), and cell growth (SVH3, LIP5). Hormone application experiments demonstrated genotype- and tissue-specific responses on trichome production, particularly to jasmonate and gibberellin.

Together, these results indicate that the CO1 locus controlling trichome abundance in B. napus is complicated and may affect regulation of chromatin state, hormonal pathways, cytoskeletal organization, and cell growth, in addition to the assembly of the trichome regulatory complex.