Suchergebnisse

Coumarate 3-hydroxylase (C3H) catalyzes a key step of the synthesis of the two main lignin subunits, guaiacyl (G) and syringyl (S) in dicotyledonous species. As no functional data are available in regards to this enzyme in monocotyledonous species, we generated C3H1 knock-down maize plants. The results obtained indicate that C3H1 participates in lignin biosynthesis as its down-regulation redirects the phenylpropanoid flux: as a result, increased amounts of p-hydroxyphenyl (H) units, lignin-associated ferulates and the flavone tricin were detected in transgenic stems cell walls. Altogether, these changes make stem cell walls more degradable in the most C3H1-repressed plants, despite their unaltered polysaccharide content. The increase in H monomers is moderate compared to C3H deficient Arabidopsis and alfalfa plants. This could be due to the existence of a second maize C3H protein (C3H2) that can compensate the reduced levels of C3H1 in these C3H1-RNAi maize plants. The reduced expression of C3H1 alters the macroscopic phenotype of the plants, whose growth is inhibited proportionally to the extent of C3H1 repression. Finally, the down-regulation of C3H1 also increases the synthesis of flavonoids, leading to the accumulation of anthocyanins in transgenic leaves. ; Funding: This work was supported by the Spanish "Ministerio de Economía y Competitividad" [AGL2011-30545-C02-01 to D.C.-R., AGL2011-30545-C02-02 to A.E., and AGL2011-25379 (co-financed by FEDER funds) to J.C.R.] and received financial support from the CONSOLIDER-INGENIO program [CSD2007-00036] from the Spanish Ministerio de Ciencia e Innovación. This work was carried out within the framework of the "Xarxa de Referència de Biotecnologia" (XarBa) from the Autonomous Government of Catalonia. R.S. was financed by the postdoctoral contracts "Isidro Parga Pondal" supported by the Autonomous Government of Galicia and the European Social Fund and "Ramón y Cajal", supported by the Spanish Ministry of Economy and Competitiveness and the University of Vigo. J.R. thanks CSIC for a JAE-DOC contract of the program "Junta para la Ampliación de Estudios" co-financed by the European Social Fund. ; Peer Reviewed