Allele-specific expression of a weeping lovegrass gene from the lignin biosynthetic pathway, caffeoyl-coenzyme A 3-O-methyltransferase

Eragrostis curvula is an important forage grass in marginal regions for its capacity to grow and develop in sandy, not very fertile soils and for its drought tolerance. However, its widespread use for animal production is limited at present since it has low forage quality. In forage species, lignin content has been recognized as one of the main factors that affects this parameter. The O-methylation at the C3 position of the phenolic ring of caffeic acid constitutes a key step in the lignin biosynthetic pathway. The enzyme caffeoyl-CoA 3-O-methyltransferase (CCoAOMT) catalyzes such methylation and is thus considered an interesting target for molecular breeding programs. Here we report the isolation of the full-length CCoAOMT cDNA from the E. curvula inflorescences library. Primers based on this sequence led to the amplification of seven unigenes from genomic DNA from cvs. Tanganyika, Don Pablo and Kromdraai. Since the major differences were located in the intron regions, these seven sequences resulted in four possible allelic forms. We further evaluated the allelic expression per tissue in cv. Tanganyika, the most variable genotype. The four alleles predicted by the genomic sequences were found to be expressed. Three of them were common to inflorescences, roots and leaves, while the other one seemed to be specific for inflorescences. The statistical analysis showed that the expression was not organ-independent. The information reported here constitutes a valuable tool for E. curvula breeding programs, aiming to alter lignin biosynthesis to improve forage quality without causing undesirable effects.