GENOMIC CHARACTERIZATION OF RICE GERMPLASM
Location: Dale Bumpers National Rice Research Center
Title: MOLECULAR MECHANISMS OF BLAST RESISTANCE GENE PI-TA MEDIATED DEFENSE RESPONSE
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: January 1, 2006
Publication Date: February 15, 2006
Citation: Jia, Y., Lin, M.J., Jia, M.H., Gubrij, K.I. 2006. Molecular mechanisms of blast resistance gene pi-ta mediated defense response [abstract]. In: Rice Technical Working Group Meeting Proceedings, February 29 - March 1, 2006, Houston, Texas. 2006. CDROM.
A better understanding the Pi-ta gene-mediated defense response will allow the development of novel strategies to control rice blast disease and obtain the new knowledge on molecular mechanisms of the gene-for-gene theory. The Pi-ta gene in rice prevents the infections of M. grisea races containing the corresponding avirulence gene AVR-Pita. Pi-ta is a putative cytoplasmic receptor that appears to directly recognize the elicitor molecule from M. grisea. AVR-Pita is predicted to encode the cognate elicitor molecule. Upon a direct recognition, a sophisticated multifaceted rapid defense response occurs in preventing further blast infection.
Katy contains the Pi-ta gene conferring resistance to M. grisea races IB-49, IC-17, IE-1, IG-1 and IH-1. To study the components in the Pi-ta gene-mediated signal pathways, a genetic screen identified 5 Katy blast susceptible mutants induced by fast neutrons. Preliminary analysis suggests that two of these mutants contain the Pi-ta gene, and three of the mutants have altered within the Pi-ta gene. All 5 mutants were susceptible to above-mentioned races. The pi-ta alleles in these mutants are being analyzed and further genetic analysis is being performed to determine the novel loci that are involved in the Pi-ta mediated defense pathways.
As an alternative approach, a yeast two-hybrid screen was used to identify potential interaction proteins in the Pi-ta pathway. Both the Pi-ta protein and AVR-Pita protein were fused in frame with GAL 4 DNA binding protein to screen a two-hybrid library made from mRNA isolated after Katy was inoculated with a M. grisea race containing AVR-Pita. An AVR-Pita interacting protein, termed AVI3, a putative transcription factor, was identified and further characterized. This gene is located on rice chromosome 1, and is induced by the fungal elicitor in rice suspension cells. Progress in analysis of the role of AVI 3 in Pi-ta-mediated signal pathways is reported.