Transcriptome-wide analysis of pathogenesis-related protein (PR) genes from Citrus latifolia Tan. Reveals its critical role during Huanglongbing disease

Huanglongbing (HLB) is a devastating citrus disease caused by the bacterium Candidatus Liberibacter asiaticus (CLas). Although Persian lime (Citrus latifolia Tan.) is considered HLB-tolerant citrus varieties, their molecular mechanisms associated with the tolerance are still unknown. The study aimed transcriptome-wide identification and bioinformatics analyses of PR genes in Persian lime (ClPRs). We identified four ClPRs genes that exhibited a highly conserved CAP, which included caveolin-binding and CAP-derived peptide motifs. The cis-acting regulatory elements associated to those ClPRs genes were associated with stress response, hormones and development responsive elements. To better understand the nature of the CLas-indiced immune response, we performed expression analyses of ClPR1.6, ClPR1.7, ClPR3.5.4 and ClPR4.3 genes in young leaves at 35 days’ post-bud initiation for the CLas infected and healthy Persian lime plants. The results showed that the expression of ClPR1.6 and ClPR4.3 genes increased their counts of expression (Transcripts Per Million; TPM) and relative expression levels in response to the increased severity HLB-disease caused by CLas-infection on Persian lime leaves. Therefore, our results suggest that the regulatory mechanisms of ClPRs genes may be the key to the tolerance exhibited by Persian lime in response to HLB disease.