Engineering for virus resistance in rice
We would like to thank research teams from the International Laboratory for Tropical Agricultural Biotechnology (ILTAB), Scripps Research Institute, USA (E. Sivamani, P. Shen, C.A. Ong, H. Huet, A. de Kochko, C. Fauquet, and R. Beachy), from CIAT, Colombia (Z. Lentini, L. Calvert, I. Lozano, E. Tabres, M. Cuervo, and E. Restrepo), and from ITH Jurich, Switzerland (J. Fütterer and I. Potrykus), for allowing access to their unpublished information. We would also like to thank W. Kositratana, Kasetsart University, Thailand, for collaboration on the RRSV genome organization study, K. Ramm, J.Gaudron, J. Gellately, M. Yang, and E. Zinkowsky for technical support, Andrew Eamens for technical editing, and Roger Hull for valuable comments on the manuscript. We gratefully acknowledge financial support from the Rockefeller Foundation for our RRSV research.
Plant viruses together with their insect vectors cause considerable losses in rice production. Several viruses attack rice plants. Resistance sources are limited or the available resistance genes are either difficult to transfer into cultivated rice or are under threat of being overcome by evolving viral strains. Pathogen-derived resistance (PDR), the expression of pathogen-derived transgenes in plants to interrupt the virus infection cycle, has been employed as an alternative strategy. This approach has given resistance in rice against rice stripe virus (RSV), rice tungro spherical virus (RTSV), rice tungro bacilliform virus (RTBV), rice ragged stunt virus (RRSV), rice hoja blanca virus (RHBV), and rice yellow mottle virus (RYMV). PDR for viruses was originally achieved using gene constructs designed to express wild-type or dysfunctional viral proteins. In many cases, however, these PDR genes appear to be operating at the RNA level associated with posttranscriptional gene silencing. Our latest research shows that viral immunity can be efficiently obtained using constructs that produce dsRNA. This approach has great promise for producing virus resistance in rice. Our experiences and those of other research groups in engineering virus resistance are also discussed.
