Chu Z, Ouyang Y, Zhang J, Yang H, Wang S
National Key Laboratory of Crop Genetic Improvement, National Center of Crop Molecular Breeding, Huazhong Agricultural University, 430070 Wuhan, China.
Mol Genet Genomics. 2004 Feb;271(1):111-20. doi: 10.1007/s00438-003-0964-6. Epub 2004 Jan 17.
Defense responses triggered by dominant and recessive disease resistance (R) genes are presumed to be regulated by different molecular mechanisms. In order to characterize the genes activated in defense responses against bacterial blight mediated by the recessive R gene xa13, two pathogen-induced subtraction cDNA libraries were constructed using the resistant rice line IRBB13--which carries xa13--and its susceptible, near-isogenic, parental line IR24. Clustering analysis of expressed sequence tags (ESTs) identified 702 unique expressed sequences as being involved in the defense responses triggered by xa13; 16% of these are new rice ESTs. These sequences define 702 genes, putatively encoding a wide range of products, including defense-responsive genes commonly involved in different host-pathogen interactions, genes that have not previously been reported to be associated with pathogen-induced defense responses, and genes (38%) with no homology to previously described functional genes. In addition, R-like genes putatively encoding nucleotide-binding site/leucine rich repeat (NBS-LRR) and LRR receptor kinase proteins were observed to be induced in the disease resistance activated by xa13. A total of 568 defense-responsive ESTs were mapped to 588 loci on the rice molecular linkage map through bioinformatic analysis. About 48% of the mapped ESTs co-localized with quantitative trait loci (QTLs) for resistance to various rice diseases, including bacterial blight, rice blast, sheath blight and yellow mottle virus. Furthermore, some defense-responsive sequences were conserved at similar locations on different chromosomes. These results reveal the complexity of xa13-mediated resistance. The information obtained in this study provides a large source of candidate genes for understanding the molecular bases of defense responses activated by recessive R genes and of quantitative disease resistance.
显性和隐性抗病（R）基因引发的防御反应被认为受不同分子机制调控。为了鉴定由隐性R基因xa13介导的对白叶枯病防御反应中被激活的基因，利用携带xa13的抗性水稻品系IRBB13及其感病的近等基因亲本品系IR24构建了两个病原体诱导的消减cDNA文库。对表达序列标签（EST）进行聚类分析，确定了702个独特的表达序列参与了xa13引发的防御反应；其中16%是新的水稻EST。这些序列定义了702个基因，推测编码广泛的产物，包括通常参与不同宿主-病原体相互作用的防御反应相关基因、以前未报道与病原体诱导的防御反应相关的基因，以及与先前描述的功能基因无同源性的基因（38%）。此外，观察到推测编码核苷酸结合位点/富含亮氨酸重复序列（NBS-LRR）和LRR受体激酶蛋白的类R基因在xa13激活的抗病反应中被诱导。通过生物信息学分析，共568个防御反应相关EST被定位到水稻分子连锁图谱的588个位点上。约48%的定位EST与抗各种水稻病害（包括白叶枯病、稻瘟病、纹枯病和黄斑驳病毒）的数量性状位点（QTL）共定位。此外，一些防御反应相关序列在不同染色体的相似位置保守。这些结果揭示了xa13介导的抗性的复杂性。本研究获得的信息为理解隐性R基因激活的防御反应的分子基础和数量抗病性提供了大量候选基因来源。
