UMR 5546, CNRS-UPS Surfaces Cellulaires et Signalisation chez les Végétaux, Castanet-Tolosan, France.
New Phytol. 2010 Nov;188(3):774-86. doi: 10.1111/j.1469-8137.2010.03432.x.
• The eucalyptus R2R3 transcription factor, EgMYB1 contains an active repressor motif in the regulatory domain of the predicted protein. It is preferentially expressed in differentiating xylem and is capable of repressing the transcription of two key lignin genes in vivo. • In order to investigate in planta the role of this putative transcriptional repressor of the lignin biosynthetic pathway, we overexpressed the EgMYB1 gene in Arabidopsis and poplar. • Expression of EgMYB1 produced similar phenotypes in both species, with stronger effects in transgenic Arabidopsis plants than in poplar. Vascular development was altered in overexpressors showing fewer lignified fibres (in phloem and interfascicular zones in poplar and Arabidopsis, respectively) and reduced secondary wall thickening. Klason lignin content was moderately but significantly reduced in both species. Decreased transcript accumulation was observed for genes involved in the biosynthesis of lignins, cellulose and xylan, the three main polymers of secondary cell walls. Transcriptomic profiles of transgenic poplars were reminiscent of those reported when lignin biosynthetic genes are disrupted. • Together, these results strongly suggest that EgMYB1 is a repressor of secondary wall formation and provide new opportunities to dissect the transcriptional regulation of secondary wall biosynthesis.
• 桉树 R2R3 转录因子 EgMYB1 在预测蛋白的调控结构域中含有一个活性抑制基序。它在木质部分化中优先表达，并且能够在体内抑制两个关键木质素基因的转录。 • 为了研究木质素生物合成途径中这个假定转录抑制剂的在植物体内的作用，我们在拟南芥和杨树中过表达了 EgMYB1 基因。 • EgMYB1 的表达在两种物种中产生了相似的表型，在转基因拟南芥植物中的影响比杨树更强。过表达植株的维管发育发生改变，表现为木质化纤维减少（在杨树和拟南芥的韧皮部和束间区分别），次生壁加厚减少。两种物种的 Klason 木质素含量均有适度但显著降低。参与木质素、纤维素和木聚糖生物合成的基因的转录物积累减少，这三种是次生细胞壁的主要聚合物。转基因杨树的转录组图谱与报道的木质素生物合成基因被破坏时的图谱相似。 • 综上所述，这些结果强烈表明 EgMYB1 是次生壁形成的抑制剂，并为解析次生壁生物合成的转录调控提供了新的机会。
