摘要
The class of nucleotide-binding site(NBS)-Leucine-rich repeat(LRR) disease resistance genes play an important role in defending plants from a variety of pathogens and insect pests. Consequently, many NBS-LRR genes have been identified in various plant species. In this study, we identified 617 NBS-encoding genes in the Medicago truncatula genome(Mt3.5v5) and divided them into two groups, regular(490) and non-regular(127) NBSLRR genes. The regular NBS-LRR genes were characterized on the bases of structural diversity, chromosomal location, gene duplication, conserved protein motifs, and EST expression profiling. According to N-terminal motifs and LRR motifs, the 490 regular NBS-LRR genes were then classified into 10 types: CC-NBS(4), CC-NBS-LRR(212), TIR-NBS(20), TIR-NBS-LRR(160), TIR-NBS-TIR(1), TIR-NBS-TIR-LRR(2), NBS-TIR(7), NBS-TIR-LRR(1), NBS(10), and NBS-LRR(73). Analysis of the physical location and duplications of the regular NBS-LRR genes revealed that the M. truncatula genome is similar to rice. Interestingly, we found that TIR-type genes are more frequently expressed than non-TIR-type genes in M. truncatula, whereas the number of non-TIR-type regular NBSLRR genes was greater than TIR-type genes, suggesting the gene expression was not associated with the total number of NBS-LRR genes. Moreover, we found that the phylogenetic tree supported our division of the regular NBS-LRR genes into two distinct clades(TIR-type and non-TIR-type), but some of the non-TIR-type lineages contain TIR-type genes. These analyses provide a robust database of NBS-LRR genes in M. truncatula that will facilitate the isolation of new resistance genes and breeding strategies to engineer disease resistance in leguminous crop.
The class of nucleotide-binding site （NBS）- Leucine-rich repeat （LRR） disease resistance genes play an important role in defending plants from a variety of pathogens and insect pests. Consequently, many NBS-LRR genes have been identified in various plant species. In this study, we identified 617 NBS-encoding genes in the Medicago truncatula genome （Mt3.5v5） and divided them into two groups, regular （490） and non-regular （127） NBS- LRR genes. The regular NBS-LRR genes were character- ized on the bases of structural diversity, chromosomal location, gene duplication, conserved protein motifs, and EST expression profiling. According to N-terminal motifs and LRR motifs, the 490 regular NBS-LRR genes were then classified into 10 types： CC-NBS （4）, CC-NBS-LRR （212）, TIR-NBS （20）, TIR-NBS-LRR （160）, TIR-NBS-TIR （1）, TIR-NBS-TIR-LRR （2）, NBS-TIR （7）, NBS-TIR-LRR （1）, NBS （10）, and NBS-LRR （73）. Analysis of the phys- ical location and duplications of the regular NBS-LRR genes revealed that the M. truncatula genome is similar to rice. Interestingly, we found that TIR-type genes are more frequently expressed than non-TIR-type genes in M. trun- catula, whereas the number of non-TIR-type regular NBS- LRR genes was greater than TIR-type genes, suggesting the gene expression was not associated with the total number of NBS-LRR genes. Moreover, we found that the phylogenetic tree supported our division of the regular NBS-LRR genes into two distinct clades （TIR-type and non-TIR-type）, but some of the non-TIR-type lineages contain TIR-type genes. These analyses provide a robust database of NBS-LRR genes in M. truncatula that will facilitate the isolation of new resistance genes and breeding strategies to engineer disease resistance in leguminous crop
基金
supported by the National Basic Research Program of China(2014CB138702)
