Small RNA profiling of Cavendish banana roots inoculated with Fusarium oxysporum f. sp. cubense race 1 and tropical race 4

Abstract

Abstract Fusarium wilt, caused by the soil-borne fungal pathogen, Fusarium oxysporum f. sp. cubense (Foc), is considered as one of the most threatening diseases of banana. The Cavendish variety, resistant to Foc race 1 (R1), is susceptible to tropical race 4 (TR4), an aggressive race of the pathogen which is of increasing concern worldwide. Previous studies have revealed that plant small RNAs (sRNAs) play crucial roles in the host response to pathogen infection. To investigate the roles of sRNAs involved in the interaction of the banana-Foc pathosystem, small RNA profiles of Cavendish banana roots inoculated with Foc TR4 and Foc R1 were obtained and analyzed in the present study using Next-Generation Sequencing (NGS) technology. A total of 112 discrete mature microRNAs (miRNAs) belonging to 22 known miRNA families were found across all constructed sRNA libraries. The expression of miR166, miR159 and miR156 was up-regulated in TR4-inoculated samples as compared to mock-inoculated samples, while the expression of these miRNAs was approximately the same in R1-inoculated and mock-inoculated samples. Consistent with the sequencing data, qRT-PCR results demonstrated up-regulation of these miRNAs and down-regulation of their target genes in TR4-inoculated samples, but not in R1-inoculated samples. Considering Cavendish banana is resistant to R1 and susceptible to TR4, it is possible that these sRNAs and their target genes are involved in particular plant defence pathways such as salicylic acid-based defence. The findings will pave way for future investigations of the defence mechanism and potential approaches of resistance improvement.

Keywords

• Banana
• Foc
• R1
• TR4
• Inoculation
• Small RNA