Changes in cell wall polymers and degradability in maize mutants lacking 30- and 50-o-methyltransferases involved in lignin biosynthesis

16 páginas.-- 7 figuras.-- 5 tablas..- 71 referencias.-- Supplementary data are available at PCP online

Caffeoyl coenzyme A 3-O-methyltransferase (CCoAOMT) and caffeic acid-O-methyltransferase (COMT) are key enzymes in the biosynthesis of coniferyl and sinapyl alcohols, the precursors of guaiacyl (G) and syringyl (S) lignin subunits. The function of these enzymes was characterized in single and double mutant maize plants. In this work, we determined that the comt (brown-midrib 3) mutant plants display a reduction of the flavonolignin unit derived from tricin (a dimethylated flavone), demonstrating that COMT is a key enzyme involved in the synthesis of this compound. In contrast, the ccoaomt1 mutants display a wild-type amount of tricin, suggesting that CCoAOMT1 is not essential for the synthesis of this compound. Based on our data, we suggest that CCoAOMT1 is involved in lignin biosynthesis at least in midribs. The phenotype of ccoaomt1 mutant plants displays no alterations, and their lignin content and composition remain unchanged. On the other hand, the ccoaomt1 comt mutant displays phenotypic and lignin alterations similar to those already described for the comt mutant. Although stems from the three mutants display a similar increase of hemicelluloses, the effect on cell wall degradability varies, the cell walls of ccoaomt1 being the most degradable. This suggests that the positive effect of lignin reduction on cell wall degradability of comt and ccoaomt1 comt mutants is counteracted by changes occurring in lignin composition, such as the decreased S/G ratio. In addition, the role of the flavonolignin unit derived from tricin in cell wall degradability is also discussed

This work was supported by the Spanish Ministry of Economy and Competitiveness [AGL2011-30545-C02-01 and AGL2014-58126-R to D.C-R., AGL2011-30545-C02-02 to A.E., BES-2012-060456 to L.G-C., AGL2011-25379 to J-C.R., AGL2014-53730-R to A.G., CTQ2014-60764-JIN co-financed by Fondo Europeo de Desarrollo Regional to J.R., and SEV-2015-0533 to D.C-R. from the Severo Ochoa Programme for Centres of Excellence in R&D 2016-2019]; the Consejo Superior de Investigaciones Científicas [201440E097 to A.G.]; the CONSOLIDER-INGENIO Programme from the Spanish Ministerio de Ciencia e Innovación [CSD2007-00036 to D.C-R.]; and by CERCA Programme / Generalitat de Catalunya and the Suport a Grups de Recerca Programme [SGR2009-GRC703 and SGR2014-1434 to D.C-R.] from the Autonomous Government of Catalonia.

Peer reviewed