AUXIN RESPONSIVE FACTOR-8 regulates development of feeding site induced by root knot nematodes in tomato.

Root-knot nematodes (RKN) from genus Meloidogyne induce the dedifferentiation of root vascular cells into giant multinucleate feeding cells. These feeding cells result from an extensive reprogramming of gene expression and auxin is known to be a key player in their development. However, little is known how the auxin signal is transmitted during giant cell development. Integrative analyses combining transcriptome and small non-coding RNA datasets with the specific sequencing of cleaved transcripts identified genes targeted by miRNAs in tomato (Solanum lycopersicum) galls. The two auxin-responsive transcription factors ARF8A and ARF8B, and their microRNA167 regulators, were identified as robust gene/miRNA pair candidates to be involved in the tomato response to M. incognita. Spatiotemporal expression analysis using promoter-GUS fusions showed the upregulation of ARF8A and ARF8B in RKN-induced feeding cells and surrounding cells. The generation and phenotyping of CRISPR mutants demonstrated the role of ARF8A and ARF8B in giant cell development and allowed the characterization of their downstream regulated genes.