Physical organization of mixed protease inhibitor gene clusters, coordinated expression and association with resistance to late blight at the StKI locus on potato chromosome III.
Protease inhibitors (PIs) play a role in plant defence against pests and pathogens as well as in plant development. Potato (Solanum tuberosum) contains abundant levels of diverse PIs. Most potato Kunitz-type inhibitor (KTI) genes map to the StKI locus on potato chromosome III, which is linked to a quantitative trait locus (QTL) for resistance to Phytophthora infestans. To elucidate the physical organization of PIs at the StKI locus, we screened bacterial artificial chromosome (BAC) libraries with KTI probes. Ten different clones were selected, sequenced and annotated. Of 100 putative genes, 22 corresponded to five PI classes. Expression analysis by quantitative real-time PCR (qRT-PCR) using PI class-specific primers in different tissues of the tetraploid potato cultivars 'Nikita' and 'Baltica' revealed different transcript levels, depending on PI type and genotype. During the compatible interaction with a complex race of P. infestans, four PI classes showed coordinated expression over 3 d after infection, a strong decrease in infected leaves and a transient induction in systemic leaves. Basal transcript levels in non-infected leaves differed strongly between the two genotypes examined. Two microsatellite markers located within the PI gene cluster were associated with resistance to P. infestans in a population of potato varieties and breeding clones.
Odeny
Damaris Achieng
DA
Max-Planck Institute for Plant Breeding Research, Köln, Germany. dodeny@arc.agric.za
Stich
Benjamin
B
Gebhardt
Christiane
C
D022202:Chromosomes, Artificial, Bacterial; D032461:Chromosomes, Plant; D017931:DNA Primers; D015870:Gene Expression; D054884:Host-Pathogen Interactions; D005810:Multigene Family; D010455:Peptides / Q000235:genetics*; D020161:Physical Chromosome Mapping; D055750:Phytophthora infestans / Q000502:physiology*; D010935:Plant Diseases / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics*; D040641:Quantitative Trait Loci; D017422:Sequence Analysis, DNA; D011198:Solanum tuberosum / Q000235:genetics* / Q000276:immunology / Q000382:microbiology
D017931:DNA Primers; C053865:Kunitz-type protease inhibitor, plant; D010455:Peptides; D010940:Plant Proteins