Identification and characterization of the VPE gene family and its expression in response to Fusarium oxysporum infection in Musa acuminata

Abstract

Panama disease, caused by Fusarium oxysporum f. sp. Cubense tropical race 4 (Foc TR4) has been the major threat for global banana production. The only effective measure to counteract the disease is by planting edible resistant cultivars which only limited to resistant Cavendish banana generated through somaclonal variation. Hence, understanding on the molecular events during Foc infection are crucial in order to develop protection strategies against panama disease. This research was undertaken to study the molecular characteristic of Musa acuminata vacuolar processing enzyme (MaVPE) – a cysteine proteinase that mediates programmed cell death; during FocTR4 infection. A total of seven MaVPE genes (designated as MaVPE1 through MaVPE7) were successfully identified through systemic in-silico analysis of DH-Pahang (AA group) banana genome. Phylogenetic study and tissues  specific analysis showed that MaVPEs could be divided into seed type or vegetative type. Real-time quantitative polymerase chain reaction (RT-qPCR) further revealed that most of MaVPE genes expression was induced after FocTR4 infection, specifically at 24 and 48 hours post inoculation (hpi). Moreover, induction of caspase-1 activity through caspase assay studies and increase of MaVPE expression through comparative proteomic analysis were also detected after inoculation with FocTR4. Consistently, inhibition of MaVPE activity through caspase-1 inhibitor reduced vacuolar membrane disintegration and decreased lesion formation of FocTR4 infected banana root. Further functional analysis in Arabidopsis VPE-null mutant, exhibited higher tolerance to FocTR4 infections and decreased cell death incidence. Taken together, our findings suggest that VPE act as a key molecule in modulating susceptibility response in FocTR4-infected plant.

Keywords: : Musa acuminata (M. acuminata); Fusarium oxysporum f. sp. Cubense (Foc); vacuolar processing enzyme (VPE); programmed cell death (PCD); panama disease.