Properties of the complementary RNA sequences associated with infection by the citrus exocortis viroid.

The citrus exocortis disease, caused by the low molecular weight viroid RNA, has recently been shown to include viroid complementary RNA in nucleic acid extracts. Purification procedures indicate the presence of viroid complementary sequences in both 2 M LiCl precipitate and 2 M LiCl supernatant fractions. These complementary sequences are detected in preparations from both the high and the low molecular weight regions of polyacrylamide gels. This population heterogeneity coupled with the subcellular distribution indicates viroid-related structures which may be involved in the processes of replication and pathogenesis.