Transcriptome analysis of lemon leaves (Citrus limon) infected by Plenodomus tracheiphilus reveals the effectiveness of Pseudomonas mediterranea in priming the plant response to mal secco disease

The use of biological control agents (BCAs) to cope with diseases has received considerable attention owing to its high efficiency and environmental safety. The aim of our study was to investigate the potential role of Pseudomonas mediterranea pretreatment in the response of lemon [Citrus limon (L.) Burm. f.] against mal secco, which is a devastating citrus disease caused by the fungus Plenodomus tracheiphilus. RNAseq analysis revealed that the fungus induced marked reprogramming of the transcriptome, but P. mediterranea pretreatment strongly reduced lemon leaf transcriptome modifications and limited the amount of fungal DNA inside the plant tissue. Furthermore, P. mediterranea prevented the downregulation of the genes involved in effector-triggered immunity (ETI) and the deregulation of genes involved in the biosynthesis and perception of the main phytohormones. To the best of our knowledge, this work represents the first report on the analysis of the P. tracheiphilus-lemon plant-BCA interaction at the molecular level.