Flores R, Navarro J A, de la Peña M, Navarro B, Ambrós S, Vera A
Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Spain.
Biol Chem. 1999 Jul-Aug;380(7-8):849-54. doi: 10.1515/BC.1999.104.
Viroids, subviral pathogens of plants, are composed of a single-stranded circular RNA of 246-399 nucleotides. Within the 27 viroids sequenced, avocado sunblotch, peach latent mosaic and chrysanthemum chlorotic mottle viroids (ASBVd, PLMVd and CChMVd, respectively) can form hammerhead structures in both of their polarity strands. These ribozymes mediate self-cleavage of the oligomeric RNAs generated in the replication through a rolling circle mechanism, whose two other steps are catalyzed by an RNA polymerase and an RNA ligase. ASBVd, and presumably PLMVd and CChMVd, replicate and accumulate in the chloroplast, whereas typical viroids replicate and accumulate in the nucleus. PLMVd and CChMVd do not adopt a rod-like or quasi rod-like secondary structure as typical viroids do but have a highly branched conformation. A pathogenicity determinant has been mapped in a defined region of the CChMVd molecule.
类病毒是植物的亚病毒病原体，由246 - 399个核苷酸的单链环状RNA组成。在已测序的27种类病毒中，鳄梨日斑类病毒、桃潜隐花叶类病毒和菊花褪绿斑驳类病毒（分别为ASBVd、PLMVd和CChMVd）在其两条极性链中均可形成锤头状结构。这些核酶通过滚环机制介导复制过程中产生的寡聚RNA的自我切割，该机制的另外两个步骤由RNA聚合酶和RNA连接酶催化。ASBVd，可能还有PLMVd和CChMVd，在叶绿体中复制和积累，而典型的类病毒在细胞核中复制和积累。PLMVd和CChMVd不像典型类病毒那样具有杆状或准杆状二级结构，而是具有高度分支的构象。一个致病性决定因素已定位在CChMVd分子的一个特定区域。
