Contribution of the satellite encoded gene βC1 to cotton leaf curl disease symptoms

Cotton leaf curl disease (CLCuD) is caused by one of seven begomoviruses in conjunction with a specific satellite; CLCuD DNA P. Associated with some monopartite begomoviruses, DNA beta components encode a single gene (beta C1) which mediates satellite functions. We have investigated the contribution the satellite, specifically beta C1, makes to CLCuD symptoms in the absence of the helper begomovirus. Systemic expression of CLCuD-beta C1 from a Potato virus X (PVX) vector induces bona fide CLCuD disease symptoms in Nicotiana tabacum plants, including enations, swollen veins and vein darkening. These contrast with the mild symptoms of PVX in this host. Analysis of thin sections across enations induced by PVX expressing beta C1 shows the structure of the enation to be identical to those induced by CLCuD DNA P in conjunction with a helper begomovirus. These results demonstrate that CLCuD beta C1 is the major determinant of symptoms for the CLCuD complex. (C) 2007 Elsevier B.V. All rights reserved.