Effect of a 24 bp homopolymeric region on the silencing of PDS in N. benthamiana leaves. (a) Position and length of NbPDS cDNA fragments used for silencing relative to the full-length NbPDS cDNA. All inserts were in the antisense orientation relative to the TRV coat protein. (b) Chlorophyll a levels in the aerial parts of plants infected with TRV-NbPDS constructs. Buffer control plants received infiltration buffer only and empty TRV plants were infected with TRV lacking a silencing insert. Chlorophyll a values for buffer, empty TRV and some constructs are also shown in Figure 1B and 2B. Bars represent mean ± SD (n = 3). (c) Photographs of representative leaves from TRV infected plants showing the extent of the photobleaching. Leaves from 345 bp and 257 bp constructs are also shown in Figure 2C.