Oligogalacturonides Prevent Rhizogenesis in rolB-Transformed Tobacco Explants by Inhibiting Auxin-Induced Expression of the rolB Gene.

Abstract

Oligogalacturonides elicit several defense responses and regulate different aspects of growth and development in plants.Many of the development-related effects of oligogaladuronides appear to be amenable to an auxin antagonist activity of these oligosaccharins. To clarify the role of oligogalacturonides in antagonizing auxin, we analyzed their effect on root formation in leaf explants of tobacco harboring the plant oncogene rolB We show here that oligogalacturonides are capable of inhibiting root morphogenesis driven by rol6 in transgenic leaf explants when this process requires exogenous auxin. Because rol6 expression is induced by auxin and dramatically altersthe response to this hormone in transformed plant cells, the inhibiting effect of oligogalacturonides could be exerted on the induction of rol6 and/or at some other auxin-requiring step(s) in rhizogenesis. We show that oligogalactumnides antagonize auxin primarily because they strongly inhibit auxin-regulated transcriptional activation of a rol6-B-glucuronidase gene fusion in both leaf explants and cultured leaf protoplasts. I n contrast, oligogalacturonides do not inhibit rhizogenesis when rol6 transcriptional activation is made independent of auxin, as shown by the lack of inhibition of root formation in leaf explants containing rol6 driven by a tetracycline-inducible promoter.

The AtrbohD-Mediated Oxidative Burst Elicited by Oligogalacturonides in Arabidopsis Is Dispensable for the Activation of Defense Responses Effective against Botrytis cinerea

“…ethz.ch) indicates that PAD3, RetOx, AtWRKY40, and CYP81F2 transcript levels increase after treatment with H 2 O 2 , suggesting that their expression may be mediated by ROS (data not shown). Transient accumulation of extracellular H 2 O 2 was previously observed in tobacco leaf explants and grapevine cells treated with OGs (Bellincampi et al, 1996;Aziz et al, 2004). To investigate whether OGs are also able to induce an apoplastic oxidative burst in Arabidopsis, we measured the release of H 2 O 2 in the culture medium of seedlings treated with these elicitors.…”

“…Transient accumulation of extracellular H 2 O 2 was previously observed in tobacco (Nicotiana tabacum) leaf explants and grapevine cells treated with OGs (Bellincampi et al, 1996;Aziz et al, 2004). Because PAD3 expression and camalexin accumulation can be induced by chemicals that generate oxidative stress (Zhao et al, 1998;Denby et al, 2005), we have investigated the hypothesis that H 2 O 2 mediates the induction of defense responses effective against B. cinerea in Arabidopsis plants treated with OGs.…”

Characterization of the Complex Locus of Bean Encoding Polygalacturonase-Inhibiting Proteins Reveals Subfunctionalization for Defense against Fungi and Insects

“…glycinea, that elute at the void volume of a low-resolution P-2 column (void b-glucan), was kindly provided by Dr. M. Hahn (University of Georgia, Athens). Elicitoractive OGs were prepared as described by Bellincampi et al (1996).…”

A domain swap approach reveals a role of the plant wall-associated kinase 1 (WAK1) as a receptor of oligogalacturonides

“…Fragments of HGA, named oligogalacturonides (OGs), function as danger signals and induce the expression of defense genes and proteins (5,(7)(8)(9)(10), protecting plants against fungal diseases (11). Besides inducing defense responses, OGs also affect several aspects of plant growth and development (5,12). Like hyaluronan fragments, OGs are regarded as host-or damage-associated molecular patterns (HAMPs or DAMPs) and their biological activity is related to their molecular size because OGs with a degree of polymerization (DP) between 10 and 15 are the most active (13,14).…”