Coordinated regulation of trichome morphogenesis and flavonoid pathway by a MYB HDZIP JAZ module in banana (Musa sp.)

Abstract

O_LITrichomes are epidermal structures that function in defence against biotic and abiotic stresses. The developmental and metabolic aspects of trichomes have not been studied in banana (Musa acuminata). In the present study, we report that banana cultivars with AAA genome contain trichomes on inflorescence stalk. C_LIO_LITranscriptome analysis of epidermal tissues of trichome-rich and trichome-free banana cultivars suggested that genes concerning defence response and specialized metabolism are differentially regulated. Based on the gene expression and phylogenetic analysis, two transcription factors, MaTFR (trichome and flavonol related R2R3-MYB) and MaHDZIV6 (HDZIP-IV), were identified as candidate regulators of trichome development. C_LIO_LIBoth genes partially complemented the glabrous phenotype of trichome-related mutants of Arabidopsis. Transient overexpression and silencing in banana embryogenic cells (ECS) suggested that both MaTFR and MaHDZIV6 regulate the transcription of flavonol biosynthesis genes and modulate flavonoids content. Furthermore, MaTFR was found to directly activate the expression of MaHDZIV6. C_LIO_LITrichome-enriched cultivars have enhanced active JA content compared to trichome-free cultivar suggesting the involvement of JA signalling in regulating trichome development. Two JAZ repressors, MaJAZ5 and MaJAZ8 interacted with MaTFR and attenuated the flavonoid biosynthesis. Our study concludes that the MYB, HDZIP-IV, and JAZ module fine-tunes the flavonoid biosynthesis and the trichome development in banana. C_LI