Transcriptome analysis reveals key genes involved in the resistance to Cryphonectria parasitica during early disease...

Chestnut blight, one of the most serious branch diseases in Castanea caused by Cryphonectria parasitica, which has ravaged across American chestnut and most of European chestnut since the early twentieth century. Interestingly, the Chinese chestnut is strongly resistant to chestnut blight, shedding light on restoring the ecological status of Castanea plants severely affected by chestnut blight. To better explore the early defense of Chinese chestnut elicited in response to C. parasitica, the early stage of infection process of C. parasitica was observed and RNA sequencing-based transcriptomic profiling of responses of the chestnut blight-resistant wild resource 'HBY-1' at 0, 3 and 9 h after C. parasitica inoculation was performed.

First, we found that 9 h was a critical period for Chinese chestnut infected by C. parasitica, which was the basis of further study on transcriptional activation of Chinese chestnut in response to chestnut blight in the early stage. In the transcriptome analysis, a total of 283 differentially expressed genes were identified between T9 h and Mock9 h, and these DEGs were mainly divided into two clusters, one of which was metabolism-related pathways including biosynthesis of secondary metabolites, phenylpropanoid biosynthesis, amino sugar and nucleotide sugar metabolism, and photosynthesis; the other was related to plant-pathogen interaction and MAPK signal transduction. Meanwhile, the two clusters of pathways could be connected through junction among phosphatidylinositol signaling system, phytohormone signaling pathway and α-Linolenic acid metabolism pathway. It is worth noting that genes associated with JA biosynthesis and metabolic pathway were significantly up-regulated, revealing that the entire JA metabolic pathway was activated in Chinese chestnut at the early stage of chestnut blight infection.

We identified the important infection nodes of C. parasitica and observed the morphological changes of Chinese chestnut wounds at the early stage of infection. In response to chestnut blight, the plant hormone and MAPK signal transduction pathways, plant-pathogen interaction pathways and metabolism-related pathways were activated at the early stage. JA biosynthesis and metabolic pathway may be particularly involved in the Chinese chestnut resistance to chestnut blight. These results contributes to verifying the key genes involved in the resistance of Chinese chestnut to C. parasitica.