Derrick P M, Barker H
Scottish Crop Research Institute, Invergowrie, Dundee, UK.
J Gen Virol. 1997 Jan;78 ( Pt 1):243-51. doi: 10.1099/0022-1317-78-1-243.
Potato leafroll luteovirus (PLRV) movement through phloem of PLRV-resistant potato clones was examined in experiments in which stem pieces were grafted either between infected rootstocks and virus-free susceptible scions or between infected scions and virus-free susceptible rootstocks. These test plants permitted either upwards or downwards virus movement into the susceptible tissue. Resistant potato clones had either host gene-mediated resistance (H-MR) or transgene-mediated resistance (T-NR, conferred by transformation with the PLRV coat protein gene) to PLRV accumulation. The rate of PLRV movement was similar whether stem tissue was taken from H-MR, T-MR or susceptible potato clones. Virus movement through two graft unions began around 7 days after grafting and was generally complete by about 14 to 16 days. Virus movement occurred soon after acquiring functional phloem continuity across grafts as demonstrated by tracing with 6(5)-carboxyfluorescein, a phloem-mobile dye. Most of the delay in virus detection after grafting probably resulted from the time necessary to develop new phloem strands across graft unions; subsequent movement of PLRV was rapid suggesting a passive process. PLRV infection was largely excluded from external phloem bundles in stem tissue of clones with either H-MR or T-MR. This trait was less pronounced as tissue aged. The mechanism limiting PLRV invasion of external phloem bundles of the T-MR clones appears to be similar to that operating in the H-MR clones. Results are discussed in the context of a proposed model of PLRV movement.
在实验中，研究了马铃薯卷叶黄化病毒（PLRV）在抗PLRV马铃薯无性系韧皮部中的移动情况。实验中，将茎段分别嫁接到受感染的砧木与无病毒的感病接穗之间，或受感染的接穗与无病毒的感病砧木之间。这些试验植株允许病毒向上或向下移动到感病组织中。抗性马铃薯无性系对PLRV积累具有宿主基因介导的抗性（H-MR）或转基因介导的抗性（T-NR，通过用PLRV外壳蛋白基因转化获得）。无论茎组织取自H-MR、T-MR还是感病马铃薯无性系，PLRV的移动速率相似。病毒通过两个嫁接结合处的移动在嫁接后约7天开始，通常在约14至16天完成。如用韧皮部可移动染料6(5)-羧基荧光素追踪所示，在嫁接后获得跨嫁接处的功能性韧皮部连续性后不久，病毒就开始移动。嫁接后病毒检测的大部分延迟可能是由于在嫁接结合处发育新的韧皮部束所需的时间；随后PLRV的移动很快，表明这是一个被动过程。在具有H-MR或T-MR的无性系茎组织中，外部韧皮部束基本排除了PLRV感染。随着组织老化，这一特性不太明显。限制T-MR无性系外部韧皮部束中PLRV入侵的机制似乎与H-MR无性系中起作用的机制相似。在提出的PLRV移动模型的背景下对结果进行了讨论。
