Functional Characterization of the Poplar R2R3-MYB Transcription Factor PtoMYB216 Involved in the Regulation of Lignin Biosynthesis during Wood Formation

Abstract

Because of the importance of wood in many industrial applications, tremendous studies have been performed on wood formation, especially in lignin biosynthesis. MYB transcription factors (TFs), which consist of a large family of plant TFs, have been reported to directly regulate lignin biosynthetic genes in a number of plants. In this study, we describe the cloning and functional characterization of PtoMYB216, a cDNA isolated from Chinese white poplar (Populus tomentosa Carr.). PtoMYB216 encodes a protein belonging to the R2R3-MYB family and displays significant similarity with other MYB factors shown to regulate lignin synthesis in Arabidopsis. Gene expression profiling studies showed that PtoMYB216 mRNA is specifically expressed during secondary wall formation in wood. The 1.8-kb promoter sequence of PtoMYB216 was fused to the GUS coding sequence and introduced into wild-type A. thaliana. GUS expression was shown to be restricted to tissues undergoing secondary cell wall formation. Overexpression of PtoMYB216 specifically activated the expression of the upstream genes in the lignin biosynthetic pathway and resulted in ectopic deposition of lignin in cells that are normally unligninified. These results suggest that PtoMYB216 is specific transcriptional activators of lignin biosynthesis and involved in the regulation of wood formation in poplar.

CmMYB19 Over-Expression Improves Aphid Tolerance in Chrysanthemum by Promoting Lignin Synthesis

“…Populus trichocarpa PtrMYB152 is known to enhance secondary cell wall thickness by elevating lignification activity [28]. The constitutive expression of the Populus tomentosa MYB gene PtoMYB216 in A. thaliana activates the expression of a number of lignin synthesis genes, and results in the deposition of lignin even in cells which are normally non-lignified in non-transgenic Arabidopsis [6]. The promoter sequences of both PAL and 4CL feature a high representation of AC elements.…”

“…The over-expression of either AtMYB58 or AtMYB63 upregulates a number of lignin synthesis genes, leading to the ectopic deposition of lignin [4]. Similarly, in poplar, the over-expression of PtoMYB216 activates the transcription of certain lignin synthesis genes, resulting in ectopic lignin deposition [6]. In contrast, the heterologous transcription of PdMYB221 in A. thaliana reduces the cell wall thickness of fibers and vessels, thereby negatively affecting secondary wall formation in the stem [7].…”

MYB Transcription Factors as Regulators of Phenylpropanoid Metabolism in Plants

“…These include AtMYB75 (also known as PAP1 [production of anthocyanin pigment1]) (Borevitz et al, 2000;Zhang et al, 2010), AtMYB61 (Newman et al 2004), PtMYB1 and PtMYB4 (pine, Pinus taeda) (Patzlaff et al, 2003a, b), PtrMYB3, PtrMYB20 and PtoMYB216 (poplar, Populus spp.) (McCarthy et al, 2010;Tian et al, 2013), and EgMYB2 (cider gum, Eucalyptus gunnii) (Goicoechea et al, 2005). Phylogenetic analysis indicates that these MYB proteins except PAP1 are all closely related to AtMYB83 and AtMYB85 (Figure 3).…”

MYB Transcription Factors as Regulators of Secondary Metabolism in Plants

“…These TFs contain EgMYB2 from Eucalyptus gunnii [102], PtoMYB216, PtrMYB20, and PtrMYB3 from Populus spp. [104,105], ZmMYB167 from Z. mays [106], PtMYB1 and PtMYB4 from Pinus taeda [107,108], and AtMYB75 and AtMYB61 from A. thaliana [28,109].…”