The rice xa5 gene for disease resistance to Xanthomonas oryzae pv. oryzae has been positionally cloned and encodes the gamma subunit of transcription factor IIA (TFIIAγ). TFIIAγ is a general eukaryotic transcription factor with no previously known role in disease resistance. xa5 is unusual in that it is recessive and does not conform to one of the typical resistance gene structural classes. Sequencing of TFIIAγ in resistant and susceptible isolines revealed two nucleotide substitutions resulting in an amino acid change between resistant and susceptible cultivars. This association was conserved across 27 resistant and nine susceptible rice lines in the Aus-Boro group.
通過圖位克隆的方法我們已經(jīng)克隆到水稻白葉枯病抗病基因xa5，其編碼一個(gè)轉(zhuǎn)錄因子IIA的γ亞基(TFIIAγ)。TFIIAγ是真核生物的通用轉(zhuǎn)錄因子，之前并沒有報(bào)道其在抗病中也發(fā)揮作用。xa5與其他抗病基因不同在于它是隱性的，與其他典型的抗病基因的結(jié)構(gòu)都不一樣。對(duì)抗病和感病品種中TFIIAγ基因進(jìn)行測(cè)序結(jié)果表明抗病和感病品種中TFIIAγ基因發(fā)生兩個(gè)堿基的置換導(dǎo)致一個(gè)氨基酸的改變。這種相關(guān)性在水稻Aus-Boro生態(tài)型中的27個(gè)抗病品種和9個(gè)感病品種中也是保守的。