The R2R3 transcription factor HlMYB8 and its role in flavonoid biosynthesis in hop (Humulus lupulus L.)

0495078 - BC 2019 RIV IE eng J - Journal Article
Kocábek, Tomáš - Mishra, Ajay Kumar - Matoušek, Jaroslav - Patzak, J. - Lomnická, Anna - Khare, Mudra - Krofta, K.
The R2R3 transcription factor HlMYB8 and its role in flavonoid biosynthesis in hop (Humulus lupulus L.).
Plant Science. Roč. 269, April (2018), s. 32-46. ISSN 0168-9452. E-ISSN 1873-2259
R&D Projects: GA ČR GA13-03037S
Institutional support: RVO:60077344
Keywords : chalcone synthase promoter * rna-seq data * molecular analysis * Bitter acids * R2R3 myb
OECD category: Plant sciences, botany
Impact factor: 3.785, year: 2018

Hop is an important source of medicinally valuable secondary metabolites including bioactive prenylated chalcones. To gain in-depth knowledge of the regulatory mechanisms of hop flavonoids biosynthesis, full-length cDNA of HlMyb8 transcription factor gene was isolated from lupulin glands. The deduced amino acid sequence of HlMyb8 showed high similarity to a flavonol-specific regulator of phenylpropanoid biosynthesis AtMYB12 from Arabidopsis thaliana. Transient expression studies and qRT-PCR analysis of transgenic hop plants overexpressing HlMyb8 revealed that HlMYB8 activates expression of chalcone synthase HlCHS_H1 as well as other structural genes from the flavonoid pathway branch leading to the production of flavonols (F3H, F'3H, FLS) but not prenylflavonoids (PT1, OMT1) or bitter acids (VPS, PT1). HlMyb8 could cross-activate Arabidopsis flavonol-specific genes but to a much lesser extent than AtMyb12. Reciprocally, AtMyb12 could cross-activate hop flavonolspecific genes. Transcriptome sequence analysis of hop leaf tissue overexpressing HlMyb8 confirmed the modulation of several other genes related to flavonoid biosynthesis pathways (PAL, 4CL, ANR, DFR, LDOX). Analysis of metabolites in hop female cones confirmed that overexpression of HlMyb8 does not increase prenylflavonoid or bitter acids content in lupulin glands. It follows from our results that HlMYB8 plays role in a competition between flavonol and prenylflavonoid or bitter acid pathways by diverting the flux of CHS_H1 gene product and thus, may influence the level of these metabolites in hop lupulin.
Permanent Link: http://hdl.handle.net/11104/0288097