Comparative transcriptome analysis of juniper branches infected by Gymnosporangium spp. highlights their different infection strategies associated with cytokinins

Abstract

AbstractBackgroundGymnosporangium asiaticumandG. yamadaecan shareJuniperus chinensisas the telial host, but the symptoms are completely different. The infection ofG. yamadaecauses the enlargement of the phloem and cortex of young branches as a gall, but not forG. asiaticum, suggesting that different molecular interaction mechanisms exist the twoGymnosporangiumspecies with junipers.ResultsComparative transcriptome analysis was performed to investigate genes regulation of juniper in responses to the infections ofG. asiaticumandG. yamadaeat different stages. Functional enrichment analysis showed that genes related to transport, catabolism and transcription pathways were up-regulated, while genes related to energy metabolism and photosynthesis were down-regulated in juniper branch tissues after infection withG. asiaticumandG. yamadae. The transcript profiling ofG. yamadae-induced gall tissues revealed that more genes involved in photosynthesis, sugar metabolism, plant hormones and defense-related pathways were up-regulated in the vigorous development stage of gall compared to the initial stage, and were eventually repressed overall. Furthermore, the concentration of cytokinins (CKs) in the galls tissue and the telia ofG. yamadaewas significantly higher than in healthy branch tissues of juniper. As well, tRNA-isopentenyltransferase (tRNA-IPT) was identified inG. yamadaewith highly expression levels during the gall development stages.ConclusionsIn general, our study provided new insights into the host-specific mechanisms by whichG. asiaticumandG. yamadaedifferentially utilize CKs and specific adaptations on juniper during their co-evolution.