Immunity-Induced Root Growth Inhibition is Mediated by Cell Cycle Arrest

Root diseases caused by pathogenic infections in agricultural crops result in significantly reduced growth and subsequently yield. Efforts to increase immunity in crops against such pathogens, however, are hampered by the fact that plant immunity itself, not just disease caused by pathogens, is associated with reduced growth, and subsequent yield reductions comparable to those caused by disease itself (Eichmann and Schäfer, 2015). It has been observed that the exogenous application of immunity elicitors – such as the flg22 peptide from bacterial flagellin – to Arabidopsis thaliana roots results in impaired root growth and development. Until recently, this growth inhibition was believed to result from reallocation of finite resources from growth towards immunity. However, the feasibility of uncoupling growth from immunity has been demonstrated by studies with the root-colonising beneficial fungus Serendipita (formerly Piriformospora) indica (Jacobs et al., 2011). Thus, we hypothesise the existence of an active mechanism of root growth suppression as a response to immunity activation.

Combining molecular and cellular biology approaches with genetic studies, we aim to understand this mechanism of immunity-induced growth inhibition and to consequently generate plants able to sustain growth under immunity. Results will be presented that support our hypothesis that arrest of the cell cycle in the root apical meristem is responsible for the growth inhibition. Furthermore, screening of cell cycle regulator mutant and overexpressing plants has led us to the discovery of lines in which growth and immunity are uncoupled. Here we present these findings and propose a model to explain how immunity interferes with root growth signalling pathways.

Eichmann, R. and Schäfer, P. (2015) Curr. Opin. Plant Biol. 26, 106–112

Jacobs, S., et al (2011) Plant Physiol. 156 (2), 726–740