Modification of lignin biosynthesis in transgenic Nicotiana through expression of an antisense O-methyltransferase gene from Populus

Abstract

An aspen lignin-specific O-methyltransferase (bi-OMT; S-adenosyl-L-methionine: caffeic acid/5-hydroxyferulic acid 3/5-O-methyltransferase, EC 2.1.1.68) antisense sequence in the form of a synthetic gene containing the cauliflower mosaic virus 35S gene sequences for enhancer elements, promoter and terminator was stably integrated into the tobacco genome and inherited in transgenic plants with a normal phenotype. Leaves and stems of the transgenes expressed the antisense RNA and the endogenous tobacco bi-OMT mRNA was suppressed in the stems. Bi-OMT activity of stems was decreased by an average of 29% in the four transgenic plants analyzed. Chemical analysis of woody tissue of stems for lignin building units indicated a reduced content of syringyl units in most of the transgenic plants, which corresponds well with the reduced activity of bi-OMT. Transgenic plants with a suppressed level of syringyl units and a level of guaiacyl units similar to control plants were presumed to have lignins of distinctly different structure than control plants. We concluded that regulation of the level of bi-OMT expression by an antisense mechanism could be a useful tool for genetically engineering plants with modified lignin without altering normal growth and development.

Brown‐midrib maize (bm1) – a mutation affecting the cinnamyl alcohol dehydrogenase gene

“…In bm1 maize, however, lignin content is reduced by 20%, despite considerable residual CAD activity. Similarly, transgenic tobacco with reduced OMT activity have little, if any, change in total lignin (Atanassova et al, 1995;Dwivedi et al, 1994), but reduction of about 45% has been described for bm3. These anomalies highlight the differences that exist between Gramineae and dicots in the lignin biosynthetic pathway and secondary phenylpropanoid metabolism.…”

Variation in Lignin Content and Composition (Mechanisms of Control and Implications for the Genetic Improvement of Plants)

“…Transgenic tobacco containing an antisense construct of either the aspen bifunctional OMT gene (Dwivedi et al, 1994) or the alfalfa OMT gene has been analyzed for lignin content and composition. The plants containing the antisense alfalfa OMT gene had a significantly lower lignin content but did not exhibit a change in the ratio of syringyl to guaiacyl units.…”

Genetic Manipulation of Condensed Tannins in Higher Plants1

“…The results presented in this paper can be compared with other examples of heterologous antisense in higher plants. Notable examples include the expression of antisense sequences of petunia (Petunia hybrida) CHS genes in tobacco (van der Krol et al, 1988) and the antisense expression of a lignin-specific O-methyltransferase from Populus tremuloides in tobacco (Dwivedi et al, 1994). In the experiments reported here, an A. majus DFR gene has been expressed in antisense orientation in L. corniculatus and phenotypes have been noted in leaf, root, and stem tissues.…”