Enhanced ethylene production and peroxidase activity in IAA-overproducing transgenic tobacco plants is associated with increased lignin content and altered lignin composition
F. Sitbon et al., Enhanced ethylene production and peroxidase activity in IAA-overproducing transgenic tobacco plants is associated with increased lignin content and altered lignin composition, PLANT SCI, 141(2), 1999, pp. 165-173
In a previous investigation, the lignin content of the xylem in the tobacco
stem was shown to be greater in transgenic IAA-overproducing line C plants
than in wild-type plants (Sitbon et al., Plant Physiol. 99 (1992) 1062-106
9). Here, we confirm this observation and also show that the lignin composi
tion in the transformants is altered, the ratio of syringyl to guaiacyl uni
ts being decreased due to an increase in guaiacyl units. Line C plants disp
layed an increased ethylene production in leaves and internodes, as well as
a greater capacity to evolve ethylene in response to wounding and exogenou
s IAA, Line C plants also had greater peroxidase (POD) activity, whereas ci
nnamyl alcohol dehydrogenase and beta-glucosidase activities were similar i
n the two genotypes. The mRNA level of a tobacco anionic POD. previously as
sociated with increased levels of lignin and related polyphenols when overe
xpressed in transgenic tobacco plants (Lagrimini, Plant Physiol. 96 (1991)
577-583), was increased in line C plants. It is suggested that the high IAA
level in the transformants, through an induction of ethylene synthesis, in
creases POD activity and hence also lignin deposition. (C) 1999 Elsevier Sc
ience Ireland Ltd. All rights reserved.