Defended to the Nines: 25 Years of Resistance Gene Cloning Identifies Nine Mechanisms for R Protein Function

Plant Cell. 2018 Feb;30(2):285-299. doi: 10.1105/tpc.17.00579. Epub 2018 Jan 30.


Plants have many, highly variable resistance (R) gene loci, which provide resistance to a variety of pathogens. The first R gene to be cloned, maize (Zea mays) Hm1, was published over 25 years ago, and since then, many different R genes have been identified and isolated. The encoded proteins have provided clues to the diverse molecular mechanisms underlying immunity. Here, we present a meta-analysis of 314 cloned R genes. The majority of R genes encode cell surface or intracellular receptors, and we distinguish nine molecular mechanisms by which R proteins can elevate or trigger disease resistance: direct (1) or indirect (2) perception of pathogen-derived molecules on the cell surface by receptor-like proteins and receptor-like kinases; direct (3) or indirect (4) intracellular detection of pathogen-derived molecules by nucleotide binding, leucine-rich repeat receptors, or detection through integrated domains (5); perception of transcription activator-like effectors through activation of executor genes (6); and active (7), passive (8), or host reprogramming-mediated (9) loss of susceptibility. Although the molecular mechanisms underlying the functions of R genes are only understood for a small proportion of known R genes, a clearer understanding of mechanisms is emerging and will be crucial for rational engineering and deployment of novel R genes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Cloning, Molecular
  • Disease Resistance / genetics*
  • Plant Diseases / immunology*
  • Plant Proteins / genetics*
  • Plants / genetics*
  • Plants / immunology
  • Zea mays / genetics
  • Zea mays / immunology


  • Plant Proteins