Spatial regulation of monolignol biosynthesis and laccase genes control developmental and stress-related lignin in flax

Abstract

BackgroundBast fibres are characterized by very thick secondary cell walls containing high amounts of cellulose and low lignin contents in contrast to the heavily lignified cell walls typically found in the xylem tissues. To improve the quality of the fiber-based products in the future, a thorough understanding of the main cell wall polymer biosynthetic pathways is required. In this study we have carried out a characterization of the genes involved in lignin biosynthesis in flax along with some of their regulation mechanisms.ResultsWe have first identified the members of the phenylpropanoid gene families through a combination of in silico approaches. The more specific lignin genes were further characterized by high throughput transcriptomic approaches in different organs and physiological conditions and their cell/tissue expression was localized in the stems, roots and leaves. Laccases play an important role in the polymerization of monolignols. This multigenic family was determined and a miRNA was identified to play a role in the posttranscriptional regulation by cleaving the transcripts of some specific genes shown to be expressed in lignified tissues. In situ hybridization also showed that the miRNA precursor was expressed in the young xylem cells located near the vascular cambium. The results obtained in this work also allowed us to determine that most of the genes involved in lignin biosynthesis are included in a unique co-expression cluster and that MYB transcription factors are potentially good candidates for regulating these genes.ConclusionsTarget engineering of cell walls to improve plant product quality requires good knowledge of the genes responsible for the production of the main polymers. For bast fiber plants such as flax, it is important to target the correct genes from the beginning since the difficulty to produce transgenic material does not make possible to test a large number of genes. Our work determined which of these genes could be potentially modified and showed that it was possible to target different regulatory pathways to modify lignification.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-017-1072-9) contains supplementary material, which is available to authorized users.

Spatial Expression and Functional Analysis of Casparian Strip Regulatory Genes in Endodermis Reveals the Conserved Mechanism in Tomato

“…Formed together with vascular tissues during evolution ( Heath, 1976 ; Enstone et al, 2003 ; Yoon et al, 2015 ), Casparian strips are present in ferns, gymnosperms and angiosperms, and some pinales ( Warmbrodt and Evert, 1979 ; Pant and Basu, 1997 ; Wu et al, 2005 ). The hydrophobic feature of Casparian strips makes it a protective structure for vascular tissues in plants which help to defend against various environmental stresses ( Stasovski and Peterson, 1993 ; Karahara et al, 2004 ; Chen et al, 2011 ; Pfister et al, 2014 ; Yang et al, 2015 ; Yoon et al, 2015 ; Kamiya et al, 2015 ; Liberman et al, 2015 ; Liska et al, 2016 ; Le Roy et al, 2017 ; Li et al, 2017 ). However, understanding of molecular regulation behind Casparian strip development is still limited in Arabidopsis , in which stereotypical root anatomy is simpler than most other species.…”

Distribution of cell-wall polysaccharides and proteins during growth of the hemp hypocotyl

“…In addition, it is now known that the post-transcriptional regulation of gene activity is regulated by specific miRNAs (Le Roy et al 2017). A precise control of both synthesis and deposition of lignin is clearly important to promote proper functioning of cells.…”

Insights into the molecular regulation of monolignol-derived product biosynthesis in the growing hemp hypocotyl

“…AtLAC17 is specifically involved in the deposition of G lignin in fibres, while the specific activity of AtLAC4 is less clear. More recently, the regulation of flax laccase expression by the microRNA miR397 has been shown [ 23 ]. The question thus arising relates to the activity of these enzymes towards the oxidation of specific lignin subunits.…”