Journal
PLANT JOURNAL
Volume 73, Issue 1, Pages 63-76Publisher
WILEY-BLACKWELL
DOI: 10.1111/tpj.12018
Keywords
F5H; lignin; MYB; secondary cell wall; transcription factor; xylem; Arabidopsis thaliana
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Funding
- FORMAS (FuncFiber/BioImprove)
- Swedish Research Council
- VINNOVA
- Bio4Energy (the Swedish programme for renewable energy)
- Universiteit Gent [AUGE/014]
- Agency for Science and Technology
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The transcription factor MYB103 was previously identified as a member of the transcriptional network regulating secondary wall biosynthesis in xylem tissues of Arabidopsis, and was proposed to act on cellulose biosynthesis. It is a direct transcriptional target of the transcription factor SECONDARY WALL ASSOCIATED NAC DOMAIN PROTEIN 1 (SND1), and 35S-driven dominant repression or over-expression of MYB103 modifies secondary wall thickness. We identified two myb103 T-DNA insertion mutants and chemically characterized their lignocellulose by pyrolysis/GC/MS, 2D NMR, FT-IR microspectroscopy and wet chemistry. The mutants developed normally but exhibited a 70-75% decrease in syringyl (S) lignin. The level of guaiacyl (G) lignin was co-ordinately increased, so that total Klason lignin was not affected. The transcript abundance of FERULATE-5-HYDROXYLASE (F5H), the key gene in biosynthesis of S lignin, was strongly decreased in the myb103 mutants, and the metabolomes of the myb103 mutant and an F5H null mutant were very similar. Other than modification of the lignin S to G ratio, there were only very minor changes in the composition of secondary cell-wall polymers in the inflorescence stem. In conclusion, we demonstrate that F5H expression and hence biosynthesis of S lignin are dependent on MYB103.
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