Expression of Critical Lignin Metabolism Genes in Flax (<I>Linum usitatissimum</I>)

Abstract

Flax (Linum usitatissimum) is an important bast fiber crop. High lignin content in the flax fiber greatly affects the per- formance and quality in the flax textile industry. CCoAOMT1, 4CL1, 4CL2, COMT, F5H1, F5H2, and F5H3 are putative genes coding the key enzymes involved in lignin accumulation. The expression patterns of these genes were analyzed by semi-quantitative RT-PCR in different flax tissues and in xylem and phloem (bark) at different development stages of the variety Baihua. The results revealed that all genes were detected to express in seedlings, roots, florescent xylem, florescent phloem, leaves, flowers, and young fruits excluding F5H1 in roots. Expression of CCoAOMT1 was consistently high in all the tissues detected. There existed complementary expression between two 4CL genes and among the three F5H genes in various tissues. In the phloem, all genes lowly expressed except for 4CL2 at florescence and highly expressed after flowering. The expression of 4CL1 was high, and that of F5H3 was low in the phloem at all stages compared with that of other genes. In the xylem, expression of 4CL1 gene was low at all the developing stages, that of F5H1 reached a peak before flowering and that of the other genes in the xylem reached the highest at 30 d after emergence of seedlings and gradually declined at late growing stages, with a sharp de- crease to very lower level after flowering. The expression of 4CL1compared with other genes was significantly higher in phloem