The antagonistic effect of Banana bunchy top virus multifunctional protein B4 against Fusarium oxysporum.

The viral-induced banana bunchy top disease and the fungal-induced banana blight are two major causes of concern for industrial scale production of bananas. Banana blight is particularly troublesome, affecting ∼80% of crops worldwide. Strict guidelines and protocols are in place in order to ameliorate the effects of this devastating disease, yet little success has been achieved. From the data presented here, we have found that Banana bunchy top virus (BBTV)-infected bananas are more resistant to Fusarium oxysporum f. sp. cubense (Foc). BBTV appears to be antagonistic towards Foc, thus improving the survivability of plants against blight. The BBTV suppressor of RNA silencing, namely protein B4, displays fungicidal properties in vitro. Furthermore, transgenic tomatoes expressing green fluorescent protein (GFP)-tagged protein B4 demonstrate enhanced resistance to F. oxysporum f. sp. lycopersici (Fol). Differential gene expression analysis indicates that increased numbers of photogenesis-related gene transcripts are present in dark-green leaves of B4-GFP-modified tomato plants relative to those found in WT plants. Conversely, the transcript abundance of immunity-related genes is substantially lower in transgenic tomatoes compared with WT plants, suggesting that plant defences may be influenced by protein B4. This viral-fungal interaction provides new insights into microbial community dynamics within a single host and has potential commercial value for the breeding of transgenic resistance to Fusarium-related blight/wilt.