Hevea brasiliensis coniferaldehyde-5-hydroxylase ( HbCAld5H ) regulates xylogenesis, structure and lignin chemistry of x
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ORIGINAL ARTICLE
Hevea brasiliensis coniferaldehyde‑5‑hydroxylase (HbCAld5H) regulates xylogenesis, structure and lignin chemistry of xylem cell wall in Nicotiana tabacum S. Pramod1,3 · Thakurdas Saha1 · K. Rekha1 · P. B. Kavi Kishor2 Received: 17 August 2020 / Accepted: 30 September 2020 © The Author(s) 2020
Abstract 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 nonhomogenous 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. Keywords Coniferaldehyde-5-hydroxylase · Hevea brasiliensis · Xylogenesis · Cell wall structure · Lignin · S/G ratio · Xylans Communicated by Günther Hahne. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00299-020-02619-8) contains supplementary material, which is available to authorized users. * S. Pramod [email protected] 1
Advanced Centre for Molecular Biology and Biotechnology, Rubber Research Institute of India, Rubber Board, Kottayam, Kerala 686009, India
2
Department of Biotechnology, Vignan’s Foundation for Science, Technology & Research, Vadlamudi, Guntur 522213, Andhra Pradesh, India
3
Present Address: Department of Forest Genetics and Plant Physiology, Umea Plant Science Centre, Swedish University of Agricultural Sciences, 901‑87 Umea, Sweden
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