P-089 - CNGC14 plays as critical role in recognising P. indica during Arabidopsis root endosymbiosis

Piriformospora indica (Syn. Serendipita indica) is a generalist root endophyte that promotes growth and fitness in many plant species. The cytosolic calcium elevation is an early host response to P. indica colonization. Expression profiling of ion channels involved in the generation of the Ca²⁺ signal revealed upregulation of AtCNGC14. CNGC14 is a 726 amino-acid long plasma membrane localized protein belonging to Group III of Arabidopsis CNGCs, with no known role in plant-microbe interaction. It is reported to have critical role in extracellular auxin mediated [Ca²⁺] _cyt elevation and root gravitropism. In our experiments, cngc14 mutants show loss of P. indica mediated growth promotion. The fungal colonization and penetration in the mutants are hindered. Moreover, the expression levels of auxin and jasmonate marker genes, as well as the accumulation of auxin and its conjugates in mutant seedlings, are impeded. Transcriptome analysis of mutant roots showed an enhanced enrichment of defense-related genes compared to WT roots, suggesting increased resistance in mutants. Further dissection of mechanistic components involved in AtCNGC14-mediated recognition of P. indica is ongoing. Our findings so far suggest that P. indica-induced non- canonical auxin signaling is vital for the recognition and establishment of a symbiotic interaction between Arabidopsis and P. indica.