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

Andrea Giordano,Zhiqian Liu,Yidong Ran,Stephen N Panter,Karen Fulgueras,Hewage Wijesinghe,German C Spangenberg,Yongjin Shang,Aidyn Mouradov,Adam M Dimech,Simone Rochfort,Nicola J Patron

doi:10.1007/s11248-014-9784-1

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.

Highlights

Dallisgrass (Paspalum dilatatum Poir.) is a C4 grass native to South America, but widely grown for forage in tropical, subtropical and warm temperate regions of the world
We describe the pattern of lignin deposition and CCR1 transcript levels during plant development and analyse the impact of down-regulating CCR1 on lignin composition and digestibility
Southern hybridisation analysis with a probe from the coding region revealed four clear bands and one doublet band in DNA digested with HindIII and five bands, one having twice the intensity of the others, can be seen in DNA digested with EcoRI and SacI (Fig. 1)

Summary

Introduction

Dallisgrass (Paspalum dilatatum Poir.) is a C4 grass native to South America, but widely grown for forage in tropical, subtropical and warm temperate regions of the world. While the forage quality of P. dilatatum is higher than that of other C4 forage grass species, digestibility of warm-season grasses is, in general, poor compared with most temperate grasses (Wilson 1994) This is due to the presence of lignin deposits in the thickwalled parenchyma bundle-sheaths around each vascular bundle (Wilson 1993). A reduction in the total lignin level and changes in monolignol composition were positively correlated with improved digestibility in the brown-midrib (bm) mutants of Z. mays as well as in transgenic plants in which caffeic acid 3-O-methyltransferase (COMT) was down-regulated (Baucher et al 1998; Casler and Vogel 1999; Piquemal et al 2002; Chen et al 2004; Hisano et al 2009; Tu et al 2010; Tamasloukht et al 2011).

Experimental procedures

Results

81 Panicum virgatum 270315104

Discussion

H Lignin