Plant Science

Pared to the Essentials

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Science  08 Feb 2008:
Vol. 319, Issue 5864, pp. 699
DOI: 10.1126/science.319.5864.699b

The RNA world is alive and well—deeply embedded in plants. Plant viruses, traveling messenger RNAs, gene-silencing RNAs, these and more are the various guises of RNA in plants. For infectious RNAs, structural motifs—sequences that form hairpins and loops and bulges—are necessary both for RNA replication and for RNA trafficking between cells. Using a genome-wide mutational analysis of potato spindle tuber viroid (PSTVd), which replicates in the host cell's nucleus, Zhong et al. have investigated what these two processes share in terms of structural motifs. Potatoes produced by plants infected by this viroid are smaller and lumpier than usual, and the viroids move through the leaf cells, into the phloem, and then on to distant parts. The PSTVd RNA adopts a rod-shaped structure, and all of the loops were essential for fully successful replication and trafficking. Loops toward one end of the rod and in the middle were critical for replication; damage to loop 11 produced viroids able to travel well but not so apt to replicate; finally, one loop in its native state actually seemed to repress replication. Comparisons with other types of viroid RNAs hint at a conservation of structure-function relationships for some loops. — PJH

Plant Cell 20, 10.1105/tpc.107.056606 (2008).

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