Callose deposition: a multifaceted plant defense response.
Callose deposition in Arabidopsis has emerged as a popular model system to quantify activity of plant immunity. However, there has been a noticeable rise in contradicting reports about the regulation of pathogen-induced callose. To address this controversy, we have examined the robustness of callose deposition under different growth conditions and in response to two different pathogen-associated molecular patterns, the flagellin epitope Flg22 and the polysaccharide chitosan. Based on a commonly used hydroponic culture system, we found that variations in growth conditions have a major impact on the plant's overall capacity to deposit callose. This environmental variability correlated with levels of hydrogen peroxide (H₂O₂) production. Depending on the growth conditions, pretreatment with abscissic acid stimulated or repressed callose deposition. Despite a similar effect of growth conditions on Flg22- and chitosan-induced callose, both responses showed differences in timing, tissue responsiveness, and colocalization with H₂O₂. Furthermore, mutant analysis revealed that Flg22- and chitosan-induced callose differ in the requirement for the NADPH oxidase RBOHD, the glucosinolate regulatory enzymes VTC1 and PEN2, and the callose synthase PMR4. Our study demonstrates that callose is a multifaceted defense response that is controlled by distinct signaling pathways, depending on the environmental conditions and the challenging pathogen-associated molecular pattern.
Luna
Estrella
E
Department of Biological Chemistry, Rothamsted Research, Harpenden AL5 2JQ UK.
Pastor
Victoria
V
Robert
Jérôme
J
Flors
Victor
V
Mauch-Mani
Brigitte
B
Ton
Jurriaan
J
D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D048271:Chitosan / Q000494:pharmacology; D000939:Epitopes / Q000633:toxicity; D005408:Flagellin / Q000633:toxicity; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000502:physiology; D005936:Glucans / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology; D036226:Seedlings; D015398:Signal Transduction / Q000502:physiology*
D029681:Arabidopsis Proteins; D000939:Epitopes; D005936:Glucans; D005408:Flagellin; D048271:Chitosan; C048306:callose; D006861:Hydrogen Peroxide