Xa21D Encodes a Receptor-Like Molecule with a Leucine-Rich Repeat Domain That Determines Race-Specific Recognition and Is Subject to Adaptive Evolution

Abstract

TitleXa21D encodes a receptor-like molecule with a leucine-rich repeat domain that determines race-specific recognition and is subject to adaptive evolution. Publication Date 1998-05-01Peer reviewed eScholarship.orgPowered by the California Digital Library University of CaliforniaThe Plant Cell, Vol. 10, 765-779, May 1998, www.plantcell.org © 1998 The rice Xa21 gene confers resistance to Xanthomonas oryzae pv oryzae in a race-specific manner. Analysis of the inheritance patterns and resistance spectra of transgenic plants carrying six Xa21 gene family members indicated that one member, designated Xa21D , displayed a resistance spectrum identical to that observed for Xa21 but conferred only partial resistance. Xa21D encodes a receptor-like protein carrying leucine-rich repeat (LRR) motifs in the presumed extracellular domain. The Xa21D transcript terminates shortly after the stop codon introduced by the retrotransposon Retrofit . Comparison of nucleotide substitutions in the LRR coding regions of Xa21 and Xa21D provided evidence of adaptive selection. Both functional and evolutionary evidence indicates that the Xa21D LRR domain controls race-specific pathogen recognition. INTRODUCTIONReceptor kinases (RKs) play a key role in important cellular processes in plants and animals (Fantl et al., 1993; Song et al., 1995;Becraft et al., 1996;Heldin and Ostman, 1996; Stein et al., 1996;Ten Dijke et al., 1996;Torii et al., 1996;Li and Chory, 1997). Three functional domains are commonly associated with RK proteins: an extracellular domain, a transmembrane domain, and an intracellular catalytic domain. Studies of animal RKs have revealed a common mechanism for RK-mediated cellular signaling (Hunter, 1995;Pawson, 1995;Heldin and Ostman, 1996). In this model, ligand binding to the extracellular receptor domain induces receptor dimerization and subsequent activation of the intracellular kinase domain. The specificity of the interaction with the ligand is controlled by amino acid residues in the extracellular domain (Heldin and Ostman, 1996). Plant RKs can be divided into six subclasses based on the protein motif in the presumed extracellular domains (Walker, 1994;Becraft et al., 1996). The largest subclass of plant RKs is the leucine-rich repeat (LRR) group, which encodes proteins with an extracellular domain containing 20 to 25 imperfect repeats of a 24-amino acid leucine-rich motif. The LRR subclass of plant RKs includes proteins that govern pollen development, plant elongation, regulation of meristem and flower development, disease resistance, and brassinosteroid signal transduction, as well as other functions that remain to be determined (Chang et al., 1992;Valon et al., 1993; Song et al., 1995;Torii et al., 1996;Clark et al., 1997;Li and Chory, 1997). Plant LRRs have also been found in secreted proteins (polygalacturonase inhibitor proteins or PGIPs) (De Lorenzo et al., 1994) and in membrane-bound resistance gene products (Dixon et al., 1996). LRR domains are present in a variety of proteins involved in peptide ligand ...

Characterization of the Cryptogein Binding Sites on Plant Plasma Membranes

“…Alternatively, it can be hypothesized that the 50-kDa protein corresponds to a truncated form of the 162-kDa protein produced by an alternative splicing of the 162-kDa glycoprotein mRNA, as has been demonstrated for SRK and eSRK glycoproteins, which constitute the functional SRK receptor involved in the sporophytic self-incompatibility response in Brassicaceae (48). Both 50-and 162-kDa glycoproteins could also correspond to the products of homologue genes, as in the Xa21 and Xa21D resistance genes, in which Xa21D encodes the cytoplasmic domain of the Xa21 protein (49). However, the existence of a truncated form conflicts with the absence of the 50-kDa crosslinked protein in experiments with BS3 and DTSSP.…”

Recombination between diverged clusters of the tomato Cf-9 plant disease resistance gene family

“…The need to generate sequence novelty is imposed by the evolution of the pathogen. Positive selection for diversification of the putative recognition domain of R genes has been revealed by the analysis of synonymous and nonsynonymous substitution rates (5,13,19,20,24).…”

Genetically engineered stem rust resistance in barley using the Rpg1 gene

“…oryzae (9). Xa was isolated by map-based cloning and its identity verified by transformation of susceptible lines and cultivars (10)(11)(12)(13). The gene translates into a protein with an LRR domain and a serinethreonine kinase domain.…”