Deep RNA-seq analysis reveals key responding aspects of wild banana relative resistance to Fusarium oxysporum f. sp. cubense tropical race 4.

Tropical race 4 of Fusarium oxysporum f. sp. cubense (FocTR4) is seriously threatening the banana industry worldwide. Resistant genotypes are present in wild relatives of banana, but little is known about the genetic and molecular mechanisms driving resistance responses. In this work, through in-depth expression analysis, we compared the responses of the resistant wild relative Musa acuminata ssp. burmanicoides (WTB) with the susceptible banana cultivar "Brizilian" (CAV, as it belongs to the Cavendish subgroup) to FocTR4 infection. Our findings showed that 1196 defense-related genes in the resistant WTB were differentially expressed genes (DEGs); only 358 defense-related DEGs were detected in CAV. DEGs related to pattern recognition receptors (PRRs) and disease resistance (R genes) were found in both genotypes, indicating the onset of both basal and specific defenses to FocTR4. Genes associated with cell wall modification exhibited a more remarkable upregulation in WTB than in CAV and might be involved in resistance during penetration steps. Our data also suggested that the high resistance of WTB is quantitatively driven with larger numbers and higher expression levels of defense-related DEGs. Fine-tuning studies to understand the resistance responses of WTB at early stages should be conducted to better support banana breeding programs. Further investigations are also required to validate the role of key genes screened in this study.