Expression of the RPM1-RIN4-RPS2 complex in two citrus species with contrasting response to Huanglongbing

Objetive/Antecedents. Persian lime (Citrus latifolia) shows a very high level of tolerance to Huanglongbing (HLB). A recent study suggests that genes from the RPM1-RIN4-RPS2 complex could be partly responsible for HLB tolerance in Persian lime, unlike other highly susceptible species such as orange (C. sinensis). The objective of this study was to compare the expression of this gene complex between orange, highly susceptible to HLB, and Persian lime, a tolerant species. Materials and Methods. Sequences of the three genes of the complex for orange and Persian lime were obtained from databases of previously published works, alignments and primer design for gene expression were performed using various bioinformatics tools. Subsequently, tissue samples from symptomatic HLB-infected orange and Persian lime were obtained and infection was confirmed. The expression of the RPM1-RIN4-RPS2 genes was compared using endpoint RT-PCR. Results. The presence of all three genes of the complex was determined in both orange and Persian lime, and it was also determined that they are highly conserved between both species. Additionally, it was observed that there is no differential expression for the RPM1 gene in symptomatic HLB tissue; however, there is a difference in the expression of the RPS2 and RIN4 genes. Conclusion. The results suggest that the contrasting response to HLB could be associated with the activity of the interaction of the RIN4 and RPS2 genes, thus, this could be of interest for citrus genetic improvement aiming at HLB control.