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Papers in Pathology Plant Pathology Department

1984

Book Review: Plant Infectious Agents

Myron K. Brakke University of Nebraska-Lincoln

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Brakke, Myron K., "Book Review: Plant Infectious Agents" (1984). Papers in Plant Pathology. 183. https://digitalcommons.unl.edu/plantpathpapers/183

This Article is brought to you for free and open access by the Plant Pathology Department at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Papers in Plant Pathology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Published in SCIENCE, New Series, Vol. 223, No. 4631 (Jan. 6, 1984), p. 45.

ology. The ideas and results are current, found in infected cells has no gaps and and some of them have not been pub- serves as the template for lished elsewhere. The emphasis is on the of four RNA's. One of these RNA's is molecular biology of plant , and genomic-sized and may be a replicative most work on this aspect of the subject is intermediate. Cauliflower mosaic included. Other aspects, such as pathol- thus has similarities to the retro- ogy, epidemiology, and control, are not viruses and possibly to hepatitis in hav- covered. There is some repetition among ing both RNA and DNA stages in the reports, and there are a few errors, but replication of its . Absence of a neither are serious drawbacks. DNA replication origin will limit its use- Among the of most interest fulness in recombinant DNA technology. to molecular biologists are the , The single-stranded DNA plant virus- which are small infectious RNA's about es are the gemini viruses. They have two 250 to 400 long. Viroids genomic DNA's of similar size, except cause serious plant diseases, such as those from Australia, which have only potato spindle tuber, citrus exocortis, one. Perhaps the Australian tradition for and cadang cadang of coconut. There are unusual flora and fauna extends to virus- no cures, and prevention is the only es. known control. Similar disease agents This book also contains research re- have not yet been found in . ports on some of the better-known plant Viroids apparently do not code for pro- viruses. Notable is the recent progress in teins or polypeptides. The mechanism by the purification of template-dependent, which they cause disease is unknown, virus-specific RNA-dependent RNA rep- though it has been postulated that they licases from infected with brome interfere with messenger RNA splicing mosaic and cowpea mosaic viruses, the or some regulatory process. Multimeric confirmation of mutations induced in forms, possibly replicative intermedi- maize by barley stripe mosaic virus, and ates, have been found in infected cells, encapsidation of RNA tran- and DNA polymerase I1 has been impli- scripts in pseudovirions of tobacco mo- cated in their replication. The demon- saic virus. As many as nine subgenomic stration by Diener and his colleagues RNA's of tobacco mosaic virus have that cloned complementary DNA dimer been reported, but published evidence of potato spindle tuber is infec- for some is scanty, and Zaitlin and co- tious opens the way for studying the workers suggest that six may be arti- effect of directed base changes on their facts. These and other observations function. promise progress in studies of interac- Virusoids are small RNA's with a tions of plant viruses and their hosts. structure similar to that of viroids, but An appendix contains 15 base se- they are always associated with a larger quences of plant viruses, viroids, viru- viral RNA. Three of the four known soids, and satellites. virusoids are reported to be necessary This is not the book to go to for for the replication of the larger RNA and exhaustive coverage or detailed experi- to be a part of the virus genome. The mental protocol, but it is excellent for a fourth virusoid appears to be more like a concise version of recent developments , that is, an extra RNA associat- in the molecular biology of plant viruses. Plant Viruses ed with a virus that is only able to MYRON K. BRAKKE replicate in cells infected by the virus. Department of Plant Pathology, Plant Infectious Agents. Viruses, Viroids, Vi- Virusoids have only been known for a University of Nebraska, rusoids, and Satellites. HUGHD. ROBERTSON,few years and have been found only in Lincoln 68583 STEPHENH. HOWELL,MILTON ZAITLIN, and Australasia. They have already been se- RUSSELLL. MALMBERG,Eds. Cold Spring quenced by Symons and colleagues, but Harbor Laboratory, Cold Spring Harbor. information on their biological activity is N.Y., 1983. x, 230 pp., illus. Paper, $23. Current Communications in Molecular Biolo- incomplete. gy. From a conference, Feb. 1983. DNA-containing plant viruses were not discovered until the late 1960's, and Traditionally, few biochemists and only a few of them have been described. molecular biologists have investigated Along with the Ti of Agrobacte- plant viruses. The number who do has rium tumefaciens, they are considered as increased during the past decade, how- possible vectors for introducing DNA ever, because of the discoveries of new into plants. Cauliflower mosaic virus is and unusual viruses, unsuspected prop- representative of the single group with a erties of well-known viruses, and vi- double-stranded DNA genome. It has roids, which are smaller than viruses. circular double-stranded DNA with one This book of summaries of reports given gap in one DNA strand and two gaps in at a meeting contains many ideas, some the other. However, a supercoiled form results, and a little history and method- in a minichromosome-like structure 6 JANUARY 1984