UDP ‐glucosyltransferase UGT 84A2/ BRT 1 is required for Arabidopsis nonhost resistance to the Asian soybean rust pathogen Phakopsora pachyrhizi

Summary Nonhost resistance ( NHR ) of plants to fungal pathogens comprises different defense layers. Epidermal penetration resistance of Arabidopsis to Phakopsora pachyrhizi requires functional PEN 1 , PEN 2 and PEN 3 genes, whereas post‐invasion resistance in the mesophyll depends on the combined functionality of PEN 2 , PAD 4 and SAG 101 . Other genetic components of Arabidopsis post‐invasion mesophyll resistance remain elusive. We performed comparative transcriptional profiling of wild‐type, pen2 and pen2 pad4 sag101 mutants after inoculation with P. pachyrhizi to identify a novel trait for mesophyll NHR . Quantitative reverse transcription‐polymerase chain reaction (RT‐qPCR) analysis and microscopic analysis confirmed the essential role of the candidate gene in mesophyll NHR . UDP ‐glucosyltransferase UGT 84A2/bright trichomes 1 ( BRT 1) is a novel component of Arabidopsis mesophyll NHR to P. pachyrhizi . BRT 1 is a putative cytoplasmic enzyme in phenylpropanoid metabolism. BRT 1 is specifically induced in pen2 with post‐invasion resistance to P. pachyrhizi . Silencing or mutation of BRT 1 increased haustoria formation in pen2 mesophyll. Yet, the brt1 mutation did not affect NHR to P. pachyrhizi in wild‐type plants. We assign a novel function to BRT 1, which is important for post‐invasion NHR of Arabidopsis to P. pachyrhizi . BRT1 might serve to confer durable resistance against P. pachyrhizi to soybean.