Key Laboratory of Eco-environments of Three Gorges Reservoir Region, Ministry of Education, Chongqing Key Laboratory of Transgenic Plant and Safety Control, Institute of Resources Botany, School of Life Sciences, Southwest University, Chongqing, China.
Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, China.
Tree Physiol. 2018 Sep 1;38(9):1424-1436. doi: 10.1093/treephys/tpy027.
Brassinosteroids (BRs) as steroid hormones play an important role in plant growth and development. However, little is known about how BRs affect secondary wall biosynthesis in woody plants. In this study, we cloned and characterized PtoDWF4, a homologus gene of Arabidopsis DWF4 encoding a cytochrome P450 protein, from Populus tomentosa. qRT-PCR analysis showed that PtoDWF4 was highly expressed in stems, especially in xylem. Overexpression of PtoDWF4 (PtoDWF4-OE) in poplar promoted growth rate and biomass yield, increased area and cell layers of xylem. Transgenic plants showed a significant increase in plant height and stem diameter compared with the wild type. In contrast, the CRISPR/Cas9-generated mutation of PtoDWF4 (PtoDWF4-KO) resulted in significantly decreased biomass production in transgenic plants. Further studies revealed that constitutive expression of PtoDWF4 up-regulated the expression of secondary cell wall (SCW) biosynthesis-related genes, whereas knock-out of PtoDWF4 down-regulated their expression. Quantitative analysis of cell wall components showed a significant increase in PtoDWF4-OE lines but a reduction in PtoDWF4-KO lines compared with wild-type plants. Taken together, our results indicate that PtoDWF4 plays a positive role in improving growth rate and elevating biomass production in poplar.
油菜素内酯（BRs）作为甾体激素，在植物生长发育中发挥着重要作用。然而，关于 BRs 如何影响木本植物次生细胞壁生物合成知之甚少。本研究从毛白杨中克隆并鉴定了拟南芥 DWF4 同源基因 PtoDWF4，该基因编码细胞色素 P450 蛋白。qRT-PCR 分析表明，PtoDWF4 在茎中，特别是在木质部中高度表达。在杨树中过表达 PtoDWF4（PtoDWF4-OE）可促进生长速率和生物量产量的增加，增加木质部的面积和细胞层数。与野生型相比，转基因植物的株高和茎径显著增加。相比之下，PtoDWF4 的 CRISPR/Cas9 基因突变（PtoDWF4-KO）导致转基因植物生物量产生明显减少。进一步研究表明，PtoDWF4 的组成型表达上调了次生细胞壁（SCW）生物合成相关基因的表达，而 PtoDWF4 的敲除则下调了它们的表达。细胞壁成分的定量分析表明，与野生型植物相比，PtoDWF4-OE 系中的 PtoDWF4 显著增加，而 PtoDWF4-KO 系中的 PtoDWF4 减少。总之，我们的研究结果表明，PtoDWF4 在提高杨树的生长速率和生物量产量方面发挥着积极作用。
