Fungal resistance mediated by maize wall‐associated kinase ZmWAK‐RLK1 correlates with reduced benzoxazinoid content
Yang P, Praz C, Li B, Singla J, Robert CAM, Kessel B, Scheuermann D, Luthi L, Ouzunova M, Erb M†, Krattinger SG† and Keller B† (2019) Fungal resistance mediated by maize wall-associated kinase ZmWAK-RLK1 correlates with reduced benzoxazinoid content. New Phytologist 221: 976-987.
Wall‐associated kinases (WAKs) have recently been
identified as major components of fungal and bacterial disease
resistance in several cereal crop species. However, the molecular
mechanisms of WAK‐mediated resistance remain largely unknown.
Here, we investigated the function of the maize gene ZmWAK‐RLK1 (Htn1) that confers quantitative resistance to northern corn leaf blight (NCLB) caused by the hemibiotrophic fungal pathogen Exserohilum turcicum.
ZmWAK‐RLK1 was found to localize to the plasma
membrane and its presence resulted in a modification of the infection
process by reducing pathogen penetration into host tissues. A
large‐scale transcriptome analysis of near‐isogenic lines (NILs)
differing for ZmWAK‐RLK1 revealed that several differentially
expressed genes are involved in the biosynthesis of the secondary
metabolites benzoxazinoids (BXs). The contents of several BXs including
DIM2BOA‐Glc were significantly lower when ZmWAK‐RLK1 is present. DIM2BOA‐Glc concentration was significantly elevated in ZmWAK‐RLK1 mutants with compromised NCLB resistance. Maize mutants that were affected in overall BXs biosynthesis or content of DIM2BOA‐Glc showed increased NCLB resistance.
We conclude that Htn1‐mediated NCLB resistance
is associated with a reduction of BX secondary metabolites. These
findings suggest a link between WAK‐mediated quantitative disease
resistance and changes in biochemical fluxes starting with