ABSTRACT
We identified in deepwater rice (Oryza sativa L.) a gene encoding a leucine-rich repeat receptor-like transmembrane protein kinase, OsTMK (O. sativa transmembrane kinase). The transcript levels of OsTMK increased in the rice internode in response to gibberellin. Expression of OsTMK was especially high in regions undergoing cell division and elongation. The kinase domain of OsTMK was enzymatically active, autophosphorylating on serine and threonine residues. A cDNA encoding a rice ortholog of a kinase-associated type 2C protein phosphatase (OsKAPP) was cloned. KAPPs are putative downstream components in kinase-mediated signal transduction pathways. The kinase interaction domain of OsKAPP was phosphorylated in vitro by the kinase domain of OsTMK. RNA gel-blot analysis indicated that the expression of OsTMK and OsKAPP was similar in different tissues of the rice plant. In protein-binding assays, OsKAPP interacted with a receptor-like protein kinase, RLK5 of Arabidopsis, but not with the protein kinase domains of the rice and maize receptor-like protein kinases Xa21 and ZmPK1, respectively.
Subject(s)
Oryza/enzymology , Oryza/genetics , Phosphoprotein Phosphatases/metabolism , Protein Kinases/biosynthesis , Protein Kinases/genetics , Amino Acid Sequence , Arabidopsis/enzymology , Arabidopsis/genetics , Arabidopsis Proteins , Base Sequence , Cloning, Molecular , DNA Primers/genetics , Enzyme Induction/drug effects , Gene Expression/drug effects , Genes, Plant , Gibberellins/pharmacology , Leucine/chemistry , Molecular Sequence Data , Phosphorylation , Protein Kinases/chemistry , Repetitive Sequences, Amino Acid , Sequence Homology, Amino AcidABSTRACT
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.
Subject(s)
Biological Evolution , Multigene Family , Oryza/genetics , Plant Proteins/biosynthesis , Plant Proteins/genetics , Protein Serine-Threonine Kinases/biosynthesis , Protein Serine-Threonine Kinases/genetics , Xanthomonas/pathogenicity , Adaptation, Physiological , Amino Acid Sequence , Dimerization , Disease Susceptibility , Evolution, Molecular , Leucine , Molecular Sequence Data , Oryza/microbiology , Oryza/physiology , Plant Diseases , Plant Proteins/chemistry , Plants, Genetically Modified , Polymerase Chain Reaction , Protein Serine-Threonine Kinases/chemistry , Receptors, Cell Surface/biosynthesis , Receptors, Cell Surface/genetics , Retroelements , Sequence Alignment , Xanthomonas/geneticsABSTRACT
The cloned rice gene, Xa21, confers resistance to multiple pathogen isolates of Xanthomonas oryzae pv. oryzae in transgenic plants. The resistance phenotype was stably transmitted to T1 progeny and inherited as a single locus. The T1 progeny were tested for resistance to 32 X. oryzae pv. oryzae isolates from eight countries. Both the engineered line and the donor line showed resistance to 29 isolates and susceptibility to three isolates. The identical resistance spectrum of both lines indicates that the presence of a single member of a multigene family, Xa21, is sufficient to confer multi-isolate resistance. The results presented here have important implications for engineering disease resistance in crop plants.