Manipulating cinnamyl alcohol dehydrogenase (CAD) expression in flax affects fibre composition and properties
1 Faculty of Biotechnology, University of Wroclaw, Przybyszewskiego 63/77, Wroclaw 51-148, Poland
2 Wroclaw Research Center EIT +, Stabłowicka 147/149, Wroclaw 54-066, Poland
3 Centre of Applied Biotechnology and Basic Sciences, Faculty of Biotechnology, Rzeszow University, Aleja Rejtana 16, Rzeszow, Poland
4 Department of Bioorganic Chemistry, Institute of Chemistry and Food Technology, Faculty of Engineering and Economics, Wroclaw University of Economics, Komandorska 118/120, Wroclaw 50-345, Poland
5 Institute of Low Temperatures and Structure Research, Polish Academy of Sciences, Okólna 2, Wrocław 50-422, Poland
6 The Plant Breeding and Acclimatization Institute (IHAR) - National Research Institute, Research Division Poznan, ul. Strzeszynska 36, Poznan 60-479, Poland
7 Linum Foundation, Stabłowicka 147/149, Wroclaw 54-066, Poland
BMC Plant Biology 2014, 14:50 doi:10.1186/1471-2229-14-50Published: 20 February 2014
In recent decades cultivation of flax and its application have dramatically decreased. One of the reasons for this is unpredictable quality and properties of flax fibre, because they depend on environmental factors, retting duration and growing conditions. These factors have contribution to the fibre composition, which consists of cellulose, hemicelluloses, lignin and pectin. By far, it is largely established that in flax, lignin reduces an accessibility of enzymes either to pectin, hemicelluloses or cellulose (during retting or in biofuel synthesis and paper production).
Therefore, in this study we evaluated composition and properties of flax fibre from plants with silenced CAD (cinnamyl alcohol dehydrogenase) gene, which is key in the lignin biosynthesis. There is evidence that CAD is a useful tool to improve lignin digestibility and/or to lower the lignin levels in plants.
Two studied lines responded differentially to the introduced modification due to the efficiency of the CAD silencing. Phylogenetic analysis revealed that flax CAD belongs to the “bona-fide” CAD family. CAD down-regulation had an effect in the reduced lignin amount in the flax fibre cell wall and as FT-IR results suggests, disturbed lignin composition and structure. Moreover introduced modification activated a compensatory mechanism which was manifested in the accumulation of cellulose and/or pectin. These changes had putative correlation with observed improved fiber’s tensile strength. Moreover, CAD down-regulation did not disturb at all or has only slight effect on flax plants’ development in vivo, however, the resistance against flax major pathogen Fusarium oxysporum decreased slightly. The modification positively affected fibre possessing; it resulted in more uniform retting.
The major finding of our paper is that the modification targeted directly to block lignin synthesis caused not only reduced lignin level in fibre, but also affected amount and organization of cellulose and pectin. However, to conclude that all observed changes are trustworthy and correlated exclusively to CAD repression, further analysis of the modified plants genome is necessary. Secondly, this is one of the first studies on the crop from the low-lignin plants from the field trail which demonstrates that such plants could be successfully cultivated in a field.