Resistance to the blast pathogen Magnaporthe oryzae is proposed to be initiated by physical binding of a putative cytoplasmic receptor encoded by a nucleotide binding site-type resistance gene, Pi-ta, to the processed elicitor encoded by the corresponding avirulence gene AVR-Pita. Here, we report the identification of a new locus, Ptr(t), that is required for Pi-ta–mediated signal recognition. A Pi-ta–expressing susceptible mutant was identified using a genetic screen. Putative mutations at Ptr(t) do not alter recognition specificity to another resistance gene, Pi-ks, in the Pi-ta homozygote, indicating that Ptr(t) is more likely specific to Pi-ta–mediated signal recognition. Genetic crosses of Pi-ta Ptr(t) and Pi-ta ptr(t) homozygotes suggest that Ptr(t) segregates as a single dominant nuclear gene. A ratio of 1:1 (resistant/susceptible) of a population of BC1 of Pi-ta Ptr(t) with pi-ta ptr(t) homozygotes indicates that Pi-ta and Ptr(t) are linked and cosegregate. Genotyping of mutants of pi-ta ptr(t) and Pi-ta Ptr(t) homozygotes using ten simple sequence repeat markers at the Pi-ta region determined that Pi-ta and Ptr(t) are located within a 9-megabase region and are of indica origin. Identification of Ptr(t) is a significant advancement in studying Pi-ta–mediated signal recognition and transduction.
對(duì)稻瘟病產(chǎn)生抗性起始于對(duì)應(yīng)的無(wú)毒基因AVR-Pita編碼的激發(fā)子和具有核苷酸結(jié)合位點(diǎn)抗性基因Pi-ta編碼的細(xì)胞質(zhì)受體特異性結(jié)合。在本研究中，我們發(fā)現(xiàn)為Pi-ta介導(dǎo)的信號(hào)識(shí)別所必須的一個(gè)新的位點(diǎn)Ptr(t)。使用遺傳篩選鑒定出一個(gè)表達(dá)Pi-ta的感病突變體。在Pi-ta純合體中并不改變Ptr(t)突變體特異性識(shí)別另一個(gè)抗性基因Pi-ks，表明Ptr(t)更可能是特異性的在Pi-ta介導(dǎo)的信號(hào)識(shí)別中發(fā)揮作用。Pi-ta Ptr(t)純合體和Pi-ta ptr(t)純合體雜交后代分離結(jié)果表明Ptr(t)是一個(gè)單顯性基因。Pi-ta Ptr(t)純合體和Pi-ta ptr(t)純合體BC1群體抗感比為1:1表明Pi-ta和Ptr(t)連鎖并且共分離。在Pi-ta位點(diǎn)周?chē)x用10個(gè)SSR標(biāo)記鑒定pi-ta ptr(t) 和Pi-ta Ptr(t)純合體基因型表明這兩個(gè)基因位于一個(gè)9Mb的區(qū)域并且都是秈型起源的。鑒定出Ptr(t)對(duì)研究Pi-ta介導(dǎo)的信號(hào)識(shí)別和傳導(dǎo)具有重要意義。
結(jié)果：分離到感病突變體；在突變體中分析Pi-ta基因。