Expression of cellulose synthase-like genes in two phenotypically distinct flax (Linum usitatissimum L.) subspecies

Cellulose synthase-like (CSL) genes encode glycosyltransferases thought to be involved in the biosynthesis of cell wall non-cellulosic polysaccharides; however, the exact function is not established yet for many of them. We performed a bioinformatics search of CSL genes in the flax genome, their phylogenetic analysis and evaluated expression of CSL genes in the course of plant development and in various plant parts. Quantitative RT-PCR was used to examine expression of CSL genes in several fiber-containing samples of two flax subspecies at seedlings, rapid growth and budding stages. One of the studied subspecies is fiber flax (cultivar Blakit) that was developed to produce high-quality fiber and another one is dehiscent flax that is not used for fiber production. Our study has revealed that the LusCSLD3 and LusCSLG3.2/3.3 genes were highly expressed in all studied samples and their expression was comparable with the expression of cellulose synthase genes involved in secondary cell wall development (LusCESA4 and LusCESA7-B) at rapid growth and budding stages. LusCSLB4 gene had a strong expression in seedling samples only. We have found that LusCSL gene expression profiles from the two phenotypically distinct flax subspecies are more different at the seedling stage than at the later developmental stages-expression of LusCSL was higher in fiber flax Blakit at the seedling stage as compared to dehiscent flax. Analysis of data from RNA-Seq experiments performed on various parts of flax plants revealed that LusCSLG with unknown substrate activity could be a specific glycosyltransferase involved in the synthesis of a non-cellulosic polysaccharide composing the fiber cell wall. Our findings lay the foundation for the understanding of the fiber cell-wall biogenesis and suggest characteristic features of this process in the cultivated flax.