CINNAMYL ALCOHOL DEHYDROGENASE-C and -D Are the Primary Genes Involved in Lignin Biosynthesis in the Floral Stem of Arabidopsis

Abstract

During lignin biosynthesis in angiosperms, coniferyl and sinapyl aldehydes are believed to be converted into their corresponding alcohols by cinnamyl alcohol dehydrogenase (CAD) and by sinapyl alcohol dehydrogenase (SAD), respectively. This work clearly shows that CAD-C and CAD-D act as the primary genes involved in lignin biosynthesis in the floral stem of Arabidopsis thaliana by supplying both coniferyl and sinapyl alcohols. An Arabidopsis CAD double mutant (cad-c cad-d) resulted in a phenotype with a limp floral stem at maturity as well as modifications in the pattern of lignin staining. Lignin content of the mutant stem was reduced by 40%, with a 94% reduction, relative to the wild type, in conventional b-O-4-linked guaiacyl and syringyl units and incorportion of coniferyl and sinapyl aldehydes. Fourier transform infrared spectroscopy demonstrated that both xylem vessels and fibers were affected. GeneChip data and real-time PCR analysis revealed that transcription of CAD homologs and other genes mainly involved in cell wall integrity were also altered in the double mutant. In addition, molecular complementation of the double mutant by tissue-specific expression of CAD derived from various species suggests different abilities of these genes/proteins to produce syringyl-lignin moieties but does not indicate a requirement for any specific SAD gene.

Free Phenols in Maize Pith and Their Relationship with Resistance to <I>Sesamia nonagrioides</I> (Lepidoptera: Noctuidae) Attack

“…Previous studies have indicated impairing different steps in monolignol biosynthesis results in reddish brown to tan stem and stalk pigmentation, including the CAD and COMT mutants examined in this study (Mackay et al 1997, Tsai et al 1998, Sibout et al 2005, Zhang et al 2006). There are differences in pith and midrib (leaf vein) coloration between bmr6 and bmr12 (Porter et al 1978, Saballos et al 2009), probably because bmr6 and bmr12 block different steps of the monolignol biosynthetic pathway.…”

FLEXIBLE CULM 1 encoding a cinnamyl-alcohol dehydrogenase controls culm mechanical strength in rice

“…The dried cell wall materials were assayed for cellulose content with the anthrone reagent (Updegraff 1969) with Whatman 3MM paper as the standard (Whatman, Maidstone, UK). The determination of lignin content was performed on the extract-free samples using the standard Klason procedure (Sibout et al 2005). The evaluation of lignin structure was assayed using the DFRC protocol (Lu and Ralph 1997).…”

“…These components originate from the polymerization of the three monolignols, the p-coumaryl, coniferyl, and sinapyl alcohols, respectively (Sibout et al 2005). The types and amount of lignin units vary across plant species, tissues, cell types, and cell wall layers and are influenced by developmental and environmental factors (Campbell and Sederoff 1996;Donaldson 2001).…”

“…Many CAD homologs have been isolated from various plant species, and they have been well studied using traditional mutants and transgenic approaches Halpin et al 1998;Sibout et al 2005;Zhang et al 2006). For example, Halpin et al (1998) reported that the natural CADdeficient mutant brown midrib1 (bm1) of maize (Zea mays) showed a reddish brown pigment in leaf midribs and stem sclerenchyma; bm1 had a 20% decrease in lignin content and better digestibility.…”

“…In Arabidopsis, Sibout et al (2003) reported that there were nine CAD-like proteins distributed among four classes based on their amino acid similarity. Studies on AtCADC and AtCADD revealed that both acted as the primary genes involved in lignin biosynthesis in the floral stem of Arabidopsis by supplying both coniferyl and sinapyl alcohols (Sibout et al 2005). Tobias and Chow (2005) recently reported that there were 12 CAD family members in rice, and four closely related members at the same locus may have been created by a recent gene duplication followed by inversion.…”