AUTHOR=Rose Laura E., Atwell Susanna , Grant Murray , Holub Eric B.

TITLE=Parallel Loss-of-Function at the RPM1 Bacterial Resistance Locus in Arabidopsis thaliana

JOURNAL=Frontiers in Plant Science

VOLUME=3

YEAR=2012

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2012.00287

DOI=10.3389/fpls.2012.00287

ISSN=1664-462X

ABSTRACT=<p>Dimorphism at the Resistance to <italic>Pseudomonas syringae</italic> pv. maculicola 1 (<italic>RPM1</italic>) locus is well documented in natural populations of <italic>Arabidopsis thaliana</italic> and has been portrayed as a long-term balanced polymorphism. The haplotype from resistant plants contains the <italic>RPM1</italic> gene, which enables these plants to recognize at least two structurally unrelated bacterial effector proteins (AvrB and AvrRpm1) from bacterial crop pathogens. A complete deletion of the <italic>RPM1</italic> coding sequence has been interpreted as a single event resulting in susceptibility in these individuals. Consequently, the ability to revert to resistance or for alternative <italic>R</italic>-gene specificities to evolve at this locus has also been lost in these individuals. Our survey of variation at the <italic>RPM1</italic> locus in a large species-wide sample of <italic>A. thaliana</italic> has revealed four new loss-of-function alleles that contain most of the intervening sequence of the RPM1 open reading frame. Multiple loss-of-function alleles may have originated due to the reported intrinsic cost to plants expressing the RPM1 protein. The frequency and geographic distribution of <italic>rpm1</italic> alleles observed in our survey indicate the parallel origin and maintenance of these loss-of-function mutations and reveal a more complex history of natural selection at this locus than previously thought.</p>