A major challenge in the development of novel industrial woody crops lies in the trade-offs underlying plant growth, wood quality and abiotic stress tolerance. Single gene modifications in perennial species often lead to improvements in only one of these three processes. However, brassinosteroids (BRs) affect these three aspects, thus a BRs biosynthesis enzyme gene, PeCPD (Populus euphratica Oliv. Constitutive Photomorphogenenic Dwarf), was selected for this goal. PeCPD was mainly expressed in stems and leaves, and showed rapid responses to salt treatment. Plant height and biomass were improved in the PeCPD overexpressed lines, which was accompanied by the promotion of xylem differentiation and the reduction of pith size, consequently improving timber quality, relative to the wild type Populus tomentosa Carr. The transgenic lines also showed higher salt tolerance relative to the wild type, as indicated by less visual injuries and lower reactive oxygen species pressure. This was partly due to increased levels of soluble protein as well as higher superoxide dismutase (SOD) activity and proline level. Our results demonstrated the PeCPD overexpression mediates the trade-off between growth and abiotic stress adaptation in woody plants. The PeCPD overexpression modified the gene expression of BRs biosynthesis and metabolic process, which enhanced BRs response as indicated by improved transcript level of BRs signaling component. Our results showed that modifying PeCPD has a great potential for jointly improving growth, timber quality and abiotic stress tolerance in woody plants.

发展新型工业木本作物的主要挑战在于植物生长，木材质量和非生物胁迫耐受性的权衡取舍。多年生物种中的单基因修饰通常仅导致这三个过程之一的改善。但是，油菜素类固醇（BRs）影响这三个方面，因此为此目的选择了一个BRs生物合成酶基因PeCPD（胡杨）。五氯苯酚主要在茎和叶中表达，并显示出对盐处理的快速反应。五氯苯酚可提高株高和生物量相对于野生型毛白杨，过表达的品系伴随着木质部分化的促进和髓尺寸的减小，从而改善了木材的品质。相较于野生型，转基因品系还显示出更高的耐盐性，这由较少的视觉损伤和较低的活性氧物种压力表明。这部分是由于可溶性蛋白水平升高以及超氧化物歧化酶（SOD）活性和脯氨酸水平升高所致。我们的结果表明，PeCPD过表达介导了木本植物生长与非生物胁迫适应之间的权衡。五氯苯酚过度表达修饰了BRs的生物合成和代谢过程的基因表达，从而增强了BRs的反应，这可以通过改善BRs信号成分的转录水平来表明。我们的结果表明，改性五氯苯二酚具有共同改善木本植物生长，木材质量和非生物胁迫耐受性的巨大潜力。