Calcium signalling induced by MAMPs (Microbe-associated molecular patterns) in Arabidopis thaliana

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Calcium is a universal signal transduction second messenger. Like flg22 in leaves, a cell wall extract (CWE) from Piriformospora indica, which mimics the growth promotion effects of the fungus, induces a rapid and transient increase in cytoplasmic Ca2+ ([Ca2+]cyt) elevation in the roots. Using transgenic Arabidopsis expressing the Ca2+ sensor aequorin, we have isolated EMS mutants impaired in their Ca2+ response to the CWE in roots or to flg22 in shoots. In addition to completing the mutant screen for the two MAMPs, the aims during the extension period are: (a) to characterize the identified mutants, demonstrate their specificity and analyse MAMP-induced downstream responses in the mutants, (b) to identify a selected number of mutated genes by map-based cloning, (c) to investigate the role of second messengers, e.g. phospholipids, as modulators of [Ca2+] in both systems, and (d) to purify the active compound from the P. indica CWE. Additionally, the cameleon system will be used to improve the resolution of calcium signature characterization. The long term goal is to link the calcium signature to downstream responses and to fill in gaps in current knowledge of calcium signalling during plant-microbe interactions.