Specific Inhibition of Lignification in Bryonia dioica

Abstract

Rubbing-induced lignification in Bryonia dioica internodes is significantly impaired by N(o-hydroxyphenyl) and N(o-aminophenyl) sulfinamoyl tertiobutyl acetate, specific inhibitors of cinamyl alcohol dehydrogenase, an enzyme which is strictly associated with lignin monomer synthesis. Along with the reduction of lignification, these inhibitors counteract the inhibition of elogtion due to rubbing. These results indicate that lignification participates in the thigmomorphogenetic growth response of Bryonia dioica internodes. In a general way, the data point to the causal role of lignification in the limitation of plant growth.Rubbing young internodes of many plants results in growth cessation and increased radial expansion of the internodes (3, 5-9, 15). In Bryonia dioica the reduced elongation has been related to changes in cell wall mechanical properties resulting from an accelerated lignification (9).Several molecules able to reduce lignification have already been defined. Phenylalanine ammonia-lyase is inhibited by aaminooxy-,3-phenylpropionic acid (1) and cinnamate 4-hydroxylase by l-aminobenzotriazole (16). Unfortunately, these two target enzymes are involved in general phenylpropanoid metabolism rather than specifically associated with lignification. In addition, phenylalanine ammonia-lyase inhibitors act also on pyridoxal phosphate enzymes involved in ethylene (10) and amino acid synthesis (2). In contrast, the reductive enzyme cinnamyl alcohol dehydrogenase is strictly associated with the synthesis oflignin monomers and is inhibited in a highly specific way by OHPAS2 and NH2PAS (4,13 The last growing internodes (± 15 mm long) were gently rubbed after 1 d inhibitor feeding. For all analyses internodes were harvested 24 or 48 h after the rubbing treatments. All experiments were repeated at least three times (results ± SE).Lignin Content. Lignin content of cell wall preparations was estimated according to the technique reported before (9). RESULTSRubbing-induced inhibition of internode elongation is significantly counteracted by treatment ofthe plants with OHPAS and NH2PAS, both supplied at the concentration of 40 ,uM (Fig. 1A).Inhibitor feeding at the concentration of 80 AM appeared toxic because of wilting of the plants within 24 h. The slight reducing effect of the inhibitors on elongation of nonrubbed internodes may be a thigmomorphogenetic response due to manipulation ofthe plants. This seems to be confirmed by a concomitant slight increase in lignin content (Fig. 1B). No significant differences

A force of nature: molecular mechanisms of mechanoperception in plants

“…Plants typically acclimate to such disturbances via developmental responses that modulate the mechanical properties of load-bearing tissues and organs. Reduction of mechanical loads on the stem is achieved, for example, by a reduction in elongation, while stem thickening, increased production of support tissues, and cell-wall lignification promote stem flexural rigidity (Biddington, 1986;Dejaegher and Boyer, 1987;Niklas 1998;Patterson, 1992;Braam, 2005;Chehab et al, 2009;Porter et al, 2009;Saidi et al, 2009;Coutand, 2010). Alternative strategies involve reducing the risk of stress-induced breakage by enhancing tissue flexibility, as observed in mechanically perturbed leaf petioles and the stems of some species (Biddington, 1986;Liu et al, 2007;Anten et al, 2010).…”

Novel thigmomorphogenetic responses in Carica papaya: touch decreases anthocyanin levels and stimulates petiole cork outgrowths

“…de Jaegher et al (1985) found that rubbing the internodes of Bryonia dioica results in increased lignin, decreased cellulose and increased activities of phenylalanine ammonia-lyase and cell wall peroxidases. Furthermore, the chemical inhibition of lignin synthesis significantly counteracts the reduction of internode elongation, suggesting a direct role of lignification in thigmomorphogenetic growth responses (de Jaegher and Boyer, 1987). Alteration of chlorophyll content has also been associated with mechanical perturbation.…”

Effects of a Mechanical Stimulation on Localization of Annexin-Like Proteins in Bryonia dioica Internodes

“…Several papers have been published concerning the mechanism that could explain the modification of B. dioica internode growth induced by a mechanical stimulus (Boyer et al, 1979(Boyer et al, , 1983(Boyer et al, , 1986De Jaegher et al, 1985;De Jaegher and Boyer, 1987;Bourgeade et al, 1991;Galaud et al, 1993;Thonat et al, 1993;Bourgeade and Boyer, 1994;Mathieu et al, 1995). Among the processes that seem to be rapidly affected by this stimulus are the modifications of plasma membrane lipids (Mathieu et al, 1995), Ca 2+ redistribution (Thonat et al, 1993), and the expression of a calmodulin gene (Galaud et al, 1993).…”

“…This process is known as thigmomorphogenesis, a developmental response in plants to a mechanical stress (Jaffé, 1973). Previous' studies have shown that this process involves a rapid increase of peroxidase activity, an acceleration of lignification (De Jaegher et al, 1985;De Jaegher and Boyer, 1987), and a transient increase of ethylene .production (Boyer et al, 1983(Boyer et al, , 1986. The external stimulation affects the plasma membrane H+-ATPase activity and induces an increase of plasma membrane fluidity with modifications of some membrane components (Bourgeade and Boyer, 1994;Mathieu et al, 1995).…”