Differential expression of genes involved in C₁ metabolism and lignin biosynthesis in wooden core and bast tissues of fibre hemp (Cannabis sativa L.)

Plants are the major source of fibres for, e.g., textile and paper applications. Fibre hemp (Cannabis sativa L.) can be grown under a wide variety of agro-ecological conditions, is resistant to weeds and pests and, in general, drought tolerant. Fibre length and content of cellulose and lignin are important quality parameters for raw material used in cordage, textile, paper, and fibreboard industries. To improve currently used hemp varieties, more knowledge about the molecular processes that underlie cell wall metabolism is needed. To study gene expression in hemp, separate cDNA libraries were constructed from developing core fibres and developing and near mature bast fibres. A cDNA microarray was constructed with 3414 randomly selected hemp cDNAs. From these a total number of 1571 sequences was obtained from the 5' ends of the cDNAs. After similarity search, 1036 unique contigs were obtained. To study differences in the genetic background of quality properties of bast and core fibres, bast and core tissues were obtained from middle parts of the stems during various developmental stages and expression of the cDNAs was analyzed. A total number of 178 clones encoding 65 proteins was found to be more highly expressed in core tissue. Most of these 65 proteins are involved in C ₁ metabolism and lignin biosynthesis. In bast tissue, a total number of 110 clones encoding 44 proteins was more highly expressed. Among these 44 proteins are arabinogalactan proteins, lipid transfer proteins, lipoxygenases, and endoxyloglucan transferases. This paper describes the identification of genes that are differentially expressed in bast fibres and wooden core tissue of hemp, and is the first step in linking the genetic background to quality differences between these two types of hemp tissue. This research may result in biotechnological approaches to increase the value of hemp grown for industrial use.