Figure 4.

Identification of the Minimal TGMV Sequences Required to Confer a Mesophyll-Invasive Phenotype.

(A) Mesophyll invasion efficiency of viruses with various combinations of the BRi noncoding region and AL23 or BL1/BR1 ORFs from either TGMV (T) or BGMV (B). Mesophyll invasion data for wild-type and hybrid viruses were taken from Table 1. All possible combinations of the three genetic elements were tested in TGMV-based hybrid viruses (TGMV genetic background, open bars) and in BGMV-based hybrid viruses (BGMV genetic background, solid bars). Wild-type TGMV and hybrid viruses that efficiently invade the mesophyll contain TGMV BRi paired with TGMV AL23 ORFs, TGMV BL1/BR1 ORFs, or both.

(B) Schematic illustration of the two BGMV-based hybrid viruses with the minimal TGMV sequences required for mesophyll invasion. The viral DNA components are shown as if linearized at the (+) strand origin of replication, with the A component on top and the B component beneath. The ORFs and noncoding regions are depicted with the symbols used in Figure 1. BGMV-specific sequences are shown with open symbols, and TGMV-specific sequences are shown with solid symbols. The mesophyll-invasive BGMV-based hybrid viruses contain either TGMV AL23 and TGMV BRi (top) or TGMV BRi and TGMV BL1/BR1 (bottom).