抗稻瘟病位点LABR＿64的起源及其分布和序列多样性

Origin, Distribution and Sequence Diversity of Rice Blast Resistance Locus LABR＿64 in Rice

【目的】研究抗病基因在水稻种群中的分布特征是培育抗病品种的基础。【方法】以水稻第9染色体上与Pi3/Pi5/Pii/Pi15等位的抗病位点LABR_64为研究对象,结合稻瘟病抗性鉴定,对该位点中包含的两个抗病基因LABR_64-1和LABR_64-2在水稻群体中的分布特征进行了研究,并对其在单子叶植物中对应的直系同源序列进行了共线性分析。【结果】LABR_64位点在水稻中存在的频率约为16%,所有存在该位点的粳稻均表现高抗病性,缺失该位点的粳稻品种均表现出高感病性,而籼稻品种中LABR_64位点存在频率低于5%,虽然其存在情况下均表现出抗病性,但大部分缺失该位点品种也表现出抗性;存在LABR_64位点的品种中,LABR_64-2基因编码序列高度保守;LABR_64起源于单子叶与双子叶植物完全分离后及单子叶植物分化早期,其在不同的单子叶植物的分化过程中一直保持着良好的共线性。【结论】粳稻抗稻瘟病表型与LABR_64-1和LABR_64-2存在与否紧密关联,而籼稻的相关性不大,表明籼稻中其他抗性基因在稻瘟病抗性过程中起主导作用;鉴于LABR_64-2的高度保守性,可根据其编码序列设计分子标记,用于高效筛选抗稻瘟病粳稻品种;LABR_64可能在不同单子叶植物抗病过程中均具有重要作用。

[Objective]A better understanding of the origin and distribution of disease resistance genes in rice germplasm is useful for breeding highly resistant varieties.[Method]We analyzed sequence diversity of the rice blast resistance locus LABR_64,which contains two homologous genes,LABR_64-1 and LABR_64-2,is located in the allelic region of Pi3/Pi5/Pii/Pi15 on rice chromosome 9.In addition,we analyzed the microsynteny of the LABR_64 orthologous region in different monocotyledons.[Result]The presence frequency(PF)of LABR_64 is 16%.All of the japonica rice cultivars carrying LABR_64 are highly resistant to rice blast and all of those without the locus are susceptible.In addition,the PF of LABR_64 in the indica subpopulation is lower than 5%.Although LABR_64 is correlated with the resistance to rice blast,many indica rice cultivars without LABR_64 are also resistant to rice blast.We also found that the LABR_64-2 sequence is much conserved.Moreover,the microsynteny analysis of the LABR_64 orthologous region in different monocotyledons indicated that LABR_64 originates after the separation of the monocotyledonous and dicotyledonous species,and at the early differentiation stage of monocotyledons.[Conclusion]The rice blast resistance phenotypes are closely correlated with the presence of the LABR_64 locus in japonica subpopulation,but not in indica,indicating that there are many other resistance loci in the indica subpopulation.The LABR_64-2 sequence can be used for developing molecular markers in marker-assisted rice blast resistance breeding.It also indicated that LABR_64 may play a role in disease resistance in different monocotyledons.