Reduced lignin content and altered lignin composition in the warm season forage grass Paspalum dilatatum by down-regulation of a Cinnamoyl CoA Reductase Gene

Abstract

C4 grasses are favoured as forage crops in warm, humid climates. The use of C4 grasses in pastures is expected to increase because the tropical belt is widening due to global climate change. While the forage quality of Paspalum dilatatum (dallisgrass) is higher than that of other C4 forage grass species, digestibility of warm-season grasses is, in general, poor compared with most temperate grasses. The presence of thick-walled parenchyma bundle-sheath cells around the vascular bundles found in the C4 forage grasses are associated with the deposition of lignin polymers in cell walls. High lignin content correlates negatively with digestibility, which is further reduced by a high ratio of syringyl (S) to guaiacyl (G) lignin subunits. Cinnamoyl-CoA reductase (CCR) catalyses the conversion of cinnamoyl CoA to cinnemaldehyde in the monolignol biosynthetic pathway and is considered to be the first step in the lignin-specific branch of the phenylpropanoid pathway. We have isolated three putative CCR1 cDNAs from P. dilatatum and demonstrated that their spatio-temporal expression pattern correlates with the developmental profile of lignin deposition. Further, transgenic P. dilatatum plants were produced in which a sense-suppression gene cassette, delivered free of vector backbone and integrated separately to the selectable marker, reduced CCR1 transcript levels. This resulted in the reduction of lignin, largely attributable to a decrease in G lignin.Electronic supplementary materialThe online version of this article (doi:10.1007/s11248-014-9784-1) contains supplementary material, which is available to authorized users.

Functional characterization of CCR in birch (Betula platyphylla × Betula pendula) through overexpression and suppression analysis

“…BpCCR1 contains the protein domain, KLWYALGK, which is similar to the conserved protein domain, KNWYCYGK, derived from Eucalyptus gunnii (Lacombe et al 1997). The third (Trp, W) and fourth (Tyr, Y) positions in this domain are found to be conserved, whereas other position can be relaxed (Escamilla-Trevino et al 2010, Barakat et al 2011, Giordano et al 2014. Surprisingly, the BpCCR1 we isolated does not share any similarity (<9% with maximal high-scoring segment pair (HSP) = 32 nt) with any other 10 CCR genes from B. platyphylla that were used for phylogenetic analysis.…”

“…Therefore, CCR is considered as the first key enzyme in the biosynthesis of monolignols and it serves as a main target for modifying lignin biosynthesis pathway (Lacombe et al 1997, Abbott et al 2002, Barakat et al 2011). Modifying CCR genes in plants has been shown to lead to changes in total lignin content and the fractions of different monolignols (Piquemal et al 1998, Goujon et al 2003, Tamasloukht et al 2011, Thevenin et al 2011 and the alternation of carbon flow between lignin and other pathways (Lacombe et al 1997, Piquemal et al 1998, Giordano et al 2014). These make the cloning and characterization of CCR gene in lignin biosynthesis of high importance and practical significance.…”

Identification of genic SSRs in jute (Corchorus capsularis, Malvaceae) and development of markers for phenylpropanoid biosynthesis genes and regulatory genes

“…The regulatory genes controlling the expression of phenylpropanoid pathway genes are equally important as they are known to influence the whole pathway (Cavallini et al., ). Modification of structural as well as regulatory genes involved in phenylpropanoid metabolism has led to lignin reduction in cell walls for better textile use and increase in degradability of biofuel crops (Dixon et al., ; Fornalé et al., ), engineering of plants for mass production of chemicals (Guterman et al., ), modification of cell wall properties of forage crops for better digestibility (Giordano et al., ) and increased resistance to pests and diseases (Mierziak et al., ; Tianpei et al., ). Therefore, development of genic markers associated with phenylpropanoid pathway genes would allow us to mine genetic variation for these target traits in elite breeding lines and eventually manipulate these using molecular breeding approaches (Valdés‐López & Hernández, ).…”

Relationships between Cell Wall Digestibility and Lignin Content as Influenced by Lignin Type and Analysis Method

“…Thus, altering the composition and structure of lignin has also been pursued as a means to improve digestibility. However, the roles of lignin composition or structure for controlling cell wall digestibility have not been clearly or consistently established across plant species (Méchin et al, 2000;Fu et al, 2011;Zhang et al, 2011;Giordano et al, 2014;Kärkönen et al, 2014;Fornalé et al, 2015Fornalé et al, , 2017Chong et al, 2016). Unfortunately, efforts to relate the composition or structure of lignin to digestibility are usually confounded by concomitant changes in plant anatomy or by shifts in the concentration and distribution of lignin or other cell wall components in plant tissues (Grabber, 2005).…”

“…As described above and discussed previously (Hatfield and Fukushima, 2005), the KL, ABSL, and related techniques have differing strengths and weakness, and thus plant improvement and evaluation programs should use several quantitation methods to assess relationships between cell wall digestibility and lignin content. A brief survey of the literature also indicates that sample preparation and analytical procedures differ widely among laboratories (Méchin et al, 2000;Fukushima and Hatfield, 2004;Fu et al, 2011;Gomes et al, 2011;Zhang et al, 2011;Goff et al, 2012;Giordano et al, 2014;Kärkönen et al, 2014;Fornalé et al, 2015;Fukushima et al, 2015;Chong et al, 2016;van der Weijde et al, 2016), and this has likely contributed to our poor understanding of how lignin characteristics influence cell wall digestibility. Therefore, researchers working with natural plant systems should critically evaluate how their approaches for preparing cell walls and running lignin and digestibility assays may affect the accuracy, utility, and interpretation of their results.…”