The seasonal activity and the effect of mechanical bending and wounding on the PtCOMT promoter in Betula pendula Roth

Abstract

In this study, 900-bp (signed as p including nucleotides -1 to -886) and partly deleted (signed as dp including nucleotides -1 to -414) COMT (caffeate/5-hydroxyferulate O-methyltransferase) promoters from Populus tremuloides Michx. were fused to the GUS reporter gene, and the tissue-specific expression patterns of the promoters were determined in Betula pendula Roth along the growing season, and as a response to mechanical bending and wounding. The main activity of the PtCOMTp- and PtCOMTdp-promoters, determined by the histochemical GUS assay, was found in the developing xylem of stems during the 8th-13th week and in the developing xylem of roots in the 13th week of the growing season. The GUS expression patterns did not differ among the xylem cell types. The PtCOMT promoter-induced GUS expression observed in phloem fibres suggests a need for PtCOMT expression and thus syringyl (S) lignin synthesis in fibre lignification. However, the PtCOMTdp-promoter induced GUS expression in stem trichomes, which may contribute to the biosynthesis of phenylpropanoid pathway-derived compounds other than lignin. Finally, a strong GUS expression was induced by the PtCOMT promoters in response to mechanical stem bending but not to wounding. The lack of major differences between the PtCOMTp- and PtCOMTdp-promoters suggests that the deleted promoter sequence (including nucleotides -415 to -886) did not contain a significant regulatory element contributing to the GUS expression in young B. pendula trees.

MicroRNAs expression patterns in the response of poplar woody root to bending stress

“…Mechanical stress significantly affects plant stability resulting detrimental for plant growth, survival, and reproduction. Recently, great improvements have been made in understanding the molecular mechanism of plant responses to mechanical stress: many mechanical stress-responsive genes have been identified in several herbaceous (Allen et al 2005) and woody plants (Lu et al 2005(Lu et al , 2008aAndersson-Gunnerås et al 2006;Tiimonen et al 2007), and the contribution of non-coding RNAs, such as microRNAs (miRNAs), in the regulatory networks governing these genes and in the overall mechanical stress response has just begun to become unravelled. In particular, a group of mechanical stress-responsive miRNAs was identified in the stem of the model tree Populus trichocarpa subjected to bending stress (Lu et al 2005(Lu et al , 2008aGriffiths-Jones et al 2008;Zhang et al 2010).…”

High-level gene expression in differentiating xylem of tobacco driven by a 2.0^|^#8201;kb Poplar COMT2 promoter and a 4^|^times;35S enhancer

“…In previous studies directed to the genetic modification of wood properties, the most widely used promoter constructs have been driven by the constitutive CaMV 35S promoter (Baucher et al 1998;Coleman et al 2008;Hu et al 1999;Zhong et al 2000). Xylemspecific promoters such as that of cinnamyl alcohol dehydrogenase (CAD) (Feuillet et al 1995;Jouanin et al 2000;Wagner et al 2009), phenylalanine ammonialyase (PAL) (Gray-Mitsumune et al 1999;Guo et al 2001), 4-coumarate: CoA ligase (4CL) (Li et al 2003), caffeoyl CoA-3-O-methyltransferase (CCoAOMT) (Chen et al 2000), and caffeate/5 hydroxyferulate Omethyltransferase (COMT) (Tiimonen et al 2007) were studied and applied to modifying wood properties. However, not all these promoters were ideal for genetic engineering of woody plants.…”

“…COMT promoters from maize, tobacco and birch were reported to be xylem-specific and responsive to diverse biotic and abiotic stresses (Capellades et al 1996;Tiimonen et al 2007;Toquin et al 2003). Here, we report on the expression of two cloned promoter fragments derived from the PtrCOMT2 gene and compare their activity using GUS as a reporter in the heterologous system of N. tabacum differentiating xylem.…”

“…Here, we report on the expression of two cloned promoter fragments derived from the PtrCOMT2 gene and compare their activity using GUS as a reporter in the heterologous system of N. tabacum differentiating xylem. We have followed the expression of these constructs in tobacco because of the relatively short time needed to obtain the differentiating xylem and the relative conservation of tissue specificity previously observed between these two species (Tiimonen et al 2007;Toquin et al 2003). We have tested these promoter fragments with and without insertion of a 4×35S enhancer (Kay et al 1987) and have found that the 2.0 kb PtrCOMT2 promoter with the 4×35S enhancer inserted in front of the promoter conferred the highest GUS expression.…”

microRNAs and Mechanical Stress

“…Through the analysis of gene expression, numerous genes were found to be involved in reaction wood formation in pine (Whetten et al 2001), cypress (Yamashita et al 2008), poplar (Wu et al 2000;Joshi 2003;Déjardin et al 2004;Sterky et al 2004;Andersson-Gunnerås et al 2006;Bhandari et al 2006;Nishikubo et al 2007;Tiimonen et al 2007), and Eucalyptus (Paux et al 2005;Lu et al 2008a). Analyzing 67 cDNA fragments cloned from a cypress species Chamaecyparis obtusa (Siebold & Zucc.)…”