Subcellular effects of broad bean wilt virus 1 infection in Nicotiana benthamiana and broad bean plants

Broad bean wilt virus 1 (BBWV-1) from the genus Fabavirus (family Secoviridae) infects many important crops worldwide. We have studied the subcellular alterations in leaf tissues of Nicotiana benthamiana and broad bean (Vicia faba) plants infected by BBWV-1 using transmission electron microscopy (TEM). In addition, we have studied the effect at the subcellular level of the BBWV-1 VP37 protein, which is a pathogenicity and host specificity determinant. For this, we agroinfiltrated N. benthamiana, and broad bean plants with two BBWV-1 infective clones, the wild type pBBWV1-wt and pBBWV1-G492C defective for VP37. Mesophyll cells infected with BBWV1-wt showed many subcellular alterations such as starch accumulation and plastoglobuli in chloroplasts, cytoplasmic vesiculation, plasmalemmasomes, vacuolar inclusion bodies, and presence of virus-like particles (VLPs) scattered in the cytoplasm in both N. benthamiana and broad bean. As differential effects, aggregated VLPs in vacuolar inclusion bodies and mitochondrial proliferation were observed in N. benthamiana but not in broad bean. TEM observation of pBBWV1-G492C infected tissues suggested that VP37 could be involved in the starch accumulation in both N. benthamiana and broad bean, and with the presence of aggregated VLPs in vacuolar inclusion bodies, plasmalemmasomes, and mitochondrial proliferation in N. benthamiana. Thus, subcellular alterations induced by BBWV-1 depended on the host species and the effect of VP37 expression was higher in N. benthamiana than in broad bean.