Key message

The HbCAld5H1 gene cloned from Hevea brasiliensis regulates the cambial activity, xylem differentiation, syringyl–guaiacyl ratio, secondary wall structure, lignification pattern and xylan distribution in xylem fibres of transgenic tobacco plants.

Abstract

Molecular characterization of lignin biosynthesis gene coniferaldehyde-5-hydroxylase (CAld5H) from Hevea brasiliensis and its functional validation was performed. Both sense and antisense constructs of HbCAld5H1 gene were introduced into tobacco through Agrobacterium-mediated genetic transformation for over expression and down-regulation of this key enzyme to understand its role affecting structural and cell wall chemistry. The anatomical studies of transgenic tobacco plants revealed the increase of cambial activity leading to xylogenesis in sense lines and considerable reduction in antisense lines. The ultra-structural studies showed that the thickness of secondary wall (S2 layer) of fibre had been decreased with non-homogenous lignin distribution in antisense lines, while sense lines showed an increase in S2 layer thickness. Maule color reaction revealed that syringyl lignin distribution in the xylem elements was increased in sense and decreased in antisense lines. The immunoelectron microscopy revealed a reduction in LM 10 and LM 11 labelling in the secondary wall of antisense tobacco lines. Biochemical studies showed a radical increase in syringyl lignin in sense lines without any significant change in total lignin content, while S/G ratio decreased considerably in antisense lines. Our results suggest that CAld5H gene plays an important role in xylogenesis stages such as cambial cell division, secondary wall thickness, xylan and syringyl lignin distribution in tobacco. Therefore, CAld5H gene could be considered as a promising target for lignin modification essential for timber quality improvement in rubber.

中文翻译：

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Hevea brasiliensis coniferaldehyde-5-hydroxylase (HbCAld5H) 调控普通烟草木质部细胞壁的木糖生成、结构和木质素化学

关键信息

从巴西橡胶树中克隆的 HbCAld5H1 基因调节转基因烟草植物木质部纤维的形成层活性、木质部分化、紫丁香基-愈创木脂比、次生壁结构、木质化模式和木聚糖分布。

抽象的

对来自巴西橡胶树的木质素生物合成基因松叶醛-5-羟化酶 (CAld5H) 进行了分子表征及其功能验证。HbCAld5H1基因的正义和反义构建体均通过农杆菌导入烟草-介导的基因转化，用于这种关键酶的过度表达和下调，以了解其影响结构和细胞壁化学的作用。转基因烟草植物的解剖学研究揭示了形成层活性的增加导致有义系中的木糖生成和反义系的显着减少。超微结构研究表明，纤维次生壁（S2层）的厚度随着反义系中木质素分布的不均匀而降低，而有义系则表现出S2层厚度的增加。Maule显色反应表明，在木质部元素中紫丁香基木质素的分布在有义系中增加而在反义系中减少。免疫电子显微镜显示在反义烟草系的次生壁中 LM 10 和 LM 11 标记减少。生化研究表明，有义系中紫丁香基木质素的急剧增加，而总木质素含量没有任何显着变化，而反义系中的 S/G 比率则显着降低。我们的结果表明CAld5H基因在烟草的形成层细胞分裂、次生壁厚、木聚糖和紫丁香基木质素分布等木质形成阶段发挥重要作用。因此，CAld5H基因可以被认为是木质素修饰的一个有希望的靶点，这对于提高橡胶木材的质量至关重要。