| Nonexpressor of pathogenesis-related genes 1(NPR1),and its paralogues NPR3 and NPR4,are bona fide salicylic acid(SA)receptors and play critical regulatory roles in plant immunity.However,comprehensive identification and analysis of the NPR1-like gene family had not been conducted so far in bread wheat and its relatives.The recently published reference genome sequences provide an opportunity for this study.Here,the NPR1-like family was identified from bread wheat and its relatives’ genomes.These putative NPR1-like genes were analyzed in detail,including molecular characterization,chromosomal distributions,phylogenetic classification,gene structures,protein domain compositions,conserved motifs and amino acid residues,and cis-regulatory elements.The collinearity analysis for NPR1-like genes was performed among bread wheat and its relatives.Furthermore,the expression pattern of TaNPR1-like genes in various tissues/organs and under biotic stress conditions was also analyzed using publicly available bread wheat RNA-sequencing(RNA-seq)datasets.Overall,these results provide an invaluable resource for further functional study of NPR1-like genes in bread wheat and its relatives.The main findings were as follows:1.Utilizing bioinformatics tools,a total of 40 putative NPR1-like genes were identified from bread wheat and its relatives’ genomes.Among them,there were 17 in Triticum aestivum,five in Triticum urartu,12 in Triticum dicoccoides,and six in Aegilops tauschii.Phylogenetic analysis showed that the 40 NPR1-like proteins,together with 40 NPR1-related proteins from other plant species,were clustered into three major clades: Clade I(AtNPR1/2 subfamily),Clade II(AtNPR3/4 subfamily)and Clade III(AtBOP1/2 subfamily).2.The chromosome mapping results indicated that the distribution of TaNPR1-like family members has chromosome preference,17 genes are located on 10 of 21 chromosomes,and most genes are located on chromosome 3 of A,B and D subgenomes.There are 9 members on chromosome 3,4 on chromosome 4,3 on chromosome 5,and 1 on chromosome 7.3.The structural feature showed that Clade I,TaNPR1-A/-B/-D and TaNPR2-A/-D,and clade II,TaNPR3-A/-B/-D and TaNPR4-A/-B/-D,contained four exons and three introns.Clade III,TaNPR5-A/-B/-D and TaNPR6-A/-B/-D,had two exons and one intron.The protein domain composition revealed that all 17 TaNPR proteins contained an N-terminal BTB/POZ domain and ANK repeats in the central region similarly to AtNPR1.However,only Clade I,TaNPR1-A/-B/-D and TaNPR2-A/-D,and Clade II,TaNPR3-A/-B/-D and TaNPR4-A/-B/-D,contained the NPR1-like C-terminal region.4.The collinearity analysis illustrated that six pairs of Aet/Ta-D orthologs were located on the same chromosomes with three on 3D,one on 4D,one on 5D,and one on 7D.Moreover,10 Td-NPRs could be mapped to bread wheat AB subgenomes on the same chromosomes with three on 3A,one on 4A,one on 5A,three on 3B,one on 4B,and one on 5B,except TdNPR2-A-2/TaNPR2-A orthologous gene pairs(TdNPR2-A-2 on 7AS,TaNPR2-A on 4AL).Furthermore,four Tu/Td-A orthologous gene pairs were located on the same chromosomes,with three on 3A and one on 4A.However,orthologous TuNPR4 was located on T.urartu chromosome 4AS,corresponding to TdNPR4-A on T.dicoccoides chromosome 4AL.On the whole,however,the NPR1-like genes had an intact collinearity among bread wheat and its relatives.5.The expression profiling showed that TaNPR5-A/-B/-D and TaNPR6-A/-B/-D in Clade III exhibited specific expression in the shoot apical meristem,internode,glume,and lemma tissues,inferring that TaNPR5-A/-B/-D and TaNPR6-A/-B/-D appear to be similarly related in growth and development to AtBOP1/2.The transcript levels of TaNPR1-A/-B/-D,TaNPR3-A/-B/-D,and TaNPR4-A/-B/-D were up-regulated after PAMP(chitin and flg22)treatment for 30 min compared with the mock group.In particular,the up-regulation extent of TaNPR1-A/-B/-D significant increased at 30 min(3 and 8 fold).In spike tissue inoculated with mock or F.graminearum,TaNPR1-A/-B/-D was up-regulated at 30 and 50 hours after inoculation(hai)compared with the mock group.Taken together,these putative candidates could be used as the preferred genes to prove their biological functions through molecular experiments in development and defense. |
