Meyers Blake C, Morgante Michele, Michelmore Richard W
Department of Vegetable Crops, University of California, Davis, CA 95616, USA.
Plant J. 2002 Oct;32(1):77-92. doi: 10.1046/j.1365-313x.2002.01404.x.
The Toll/interleukin-1 receptor (TIR) domain is found in one of the two large families of homologues of plant disease resistance proteins (R proteins) in Arabidopsis and other dicotyledonous plants. In addition to these TIR-NBS-LRR (TNL) R proteins, we identified two families of TIR-containing proteins encoded in the Arabidopsis Col-0 genome. The TIR-X (TX) family of proteins lacks both the nucleotide-binding site (NBS) and the leucine rich repeats (LRRs) that are characteristic of the R proteins, while the TIR-NBS (TN) proteins contain much of the NBS, but lack the LRR. In Col-0, the TX family is encoded by 27 genes and three pseudogenes; the TN family is encoded by 20 genes and one pseudogene. Using massively parallel signature sequencing (MPSS), expression was detected at low levels for approximately 85% of the TN-encoding genes. Expression was detected for only approximately 40% of the TX-encoding genes, again at low levels. Physical map data and phylogenetic analysis indicated that multiple genomic duplication events have increased the numbers of TX and TN genes in Arabidopsis. Genes encoding TX, TN and TNL proteins were demonstrated in conifers; TX and TN genes are present in very low numbers in grass genomes. The expression, prevalence, and diversity of TX and TN genes suggests that these genes encode functional proteins rather than resulting from degradation or deletions of TNL genes. These TX and TN proteins could be plant analogues of small TIR-adapter proteins that function in mammalian innate immune responses such as MyD88 and Mal.
Toll/白细胞介素-1受体（TIR）结构域存在于拟南芥和其他双子叶植物中植物抗病蛋白（R蛋白）的两个大的同源家族之一中。除了这些TIR-NBS-LRR（TNL）R蛋白外，我们在拟南芥Col-0基因组中鉴定出了两个含TIR的蛋白家族。TIR-X（TX）蛋白家族既缺乏R蛋白特有的核苷酸结合位点（NBS），也缺乏富含亮氨酸的重复序列（LRR），而TIR-NBS（TN）蛋白含有大部分NBS，但缺乏LRR。在Col-0中，TX家族由27个基因和3个假基因编码；TN家族由20个基因和1个假基因编码。使用大规模平行签名测序（MPSS），大约85%的TN编码基因检测到低水平表达。仅约40%的TX编码基因检测到表达，同样是低水平。物理图谱数据和系统发育分析表明，多个基因组重复事件增加了拟南芥中TX和TN基因的数量。在针叶树中证明了编码TX、TN和TNL蛋白的基因；TX和TN基因在禾本科植物基因组中的数量非常少。TX和TN基因的表达、普遍性和多样性表明，这些基因编码功能性蛋白，而不是TNL基因降解或缺失的结果。这些TX和TN蛋白可能是在哺乳动物先天免疫反应（如MyD88和Mal）中起作用的小TIR衔接蛋白的植物类似物。
