The architecture of Phaseolus vulgaris root is altered when a defense response is elicited by an oligogalacturonide

Abstract

Phytoalexin accumulation is one of a myriad of plant defense responses; these responses can be elicited by pathogens or molecules such as oligogalacturonides (OGAs). Phytoalexin production has been considered a vital component of the resistance mechanisms that determine the outcome of many plant-microbe interactions. Besides inducing defense responses, OGAs have been shown to affect plant development, which normally is controlled by plant hormones, particularly auxin. In this work we measured phytoalexin accumulation in roots of bean (Phaseolus vulgaris L.) seedlings grown in the presence or absence of the auxin 3-naphtalenacetic acid (NAA) and treated with a decagalacturonide (OGA10). We found that OGA10 (0.01 mM) caused phytoalexin production and also inhibited main root elongation and the formation of secondary roots by ca. 33%. Expression of Cycb 2-2 was also inhibited, while pal and chs were highly expressed. The root growth inhibition was not overcome by the addition of a stimulatory concentration of auxin (NAA 0.1 µM). The data suggests that elicitation of defense responses in the root alters metabolism in such a way that results in the modification of the architecture of bean roots.