Location: Fruit and Tree Nut ResearchTitle: Reprogramming of a defense signaling pathway in rough lemon and sweet orange is a critical element of the early response to ‘Candidatus Liberibacter asiaticus’
|YU, QIBIN - Florida Department Of Citrus|
|DU, DONGLIANG - University Of Florida|
|HUANG, MING - University Of Florida|
|YAO, JIQIANG - University Of Florida|
|YU, FAHONG - University Of Florida|
|BRLANSKY, RONALD - University Of Florida|
|GMITTER JR., FRED - University Of Florida|
Submitted to: Horticulture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2017
Publication Date: 11/29/2017
Citation: Yu, Q., Chen, C., Du, D., Huang, M., Yao, J., Yu, F., Brlansky, R.H., Gmitter Jr., F.G. 2017. Reprogramming of a defense signaling pathway in rough lemon and sweet orange is a critical element of the early response to ‘Candidatus Liberibacter asiaticus’. Horticulture Research. 4, 17063. https://doi.org/10.1038/hortres.2017.63.
Interpretive Summary: Huanglongbing (HLB) is the most devastating citrus disease that causes tremendous loss to citrus industry. It has no cure or resistance germplasm. While sweet orange is one of the most susceptible citrus, rough lemon is considered one of the most tolerant citrus as infected rough lemon trees can rejuvenate and continue producing at certain levels. Comparison of global gene expression may help find the transcriptional differences between tolerance and susceptibility, which are often affected by the speed and intensity of defense response to a pathogen. This study revealed genes involved in some critical defense signaling pathway were highly upregulated in rough lemon, which may lead to a greater and stronger quantitative disease resistance response in rough lemon than in sweet orange and hence contribute to the durable tolerance to HLB observed in rough lemon.
Technical Abstract: Huanglongbing (HLB) in citrus infected by Candidatus Liberibacter asiaticus (CLas) has caused tremendous losses to the citrus industry. No resistant genotypes have been identified in citrus species or close relatives. Among citrus varieties, rough lemon (Citrus jambhiri) has been considered tolerant due to its ability to produce a healthy flush of new growth after infection. The difference between tolerance and susceptibility is often defined by the speed and intensity of a plant’s response to a pathogen, especially early defense responses. RNA-seq data were collected from three biological replicates of CLas- and mock-inoculated rough lemon and sweet orange (C. sinenesis) at week 0 and 7 following infection. Functional analysis of the differentially expressed genes (DEGs) indicated that genes involved in the mitogen activated protein kinase (MAPK) signaling pathway were highly upregulated in rough lemon. MAPK induces of the transcription of WRKY and other transcription factors which potentially turn on multiple defense-related genes. A Subnetwork Enrichment Analysis further revealed different patterns of regulation of several functional categories, suggesting DEGs with different functions were subjected to reprogramming. In general, the amplitude of the expression of defense-related genes is much greater in rough lemon than in sweet orange. A quantitative disease resistance response may contribute to the durable tolerance level to HLB observed in rough lemon.