Search

Southern rice black-streaked dwarf virus (SRBSDV) is a recently emerged rice virus that has spread across Asia. This devastating virus causes rice plants to produce a variety of symptoms during different growth stages. MicroRNAs (miRNAs) comprise a large group of 21-24-nt RNA molecules that are important regulators of plant development processes and stress responses. In this study, we used microarray profiling to investigate rice miRNAs responding to SRBSDV infection at 3, 9, 15, and 20 days post-inoculation (dpi). Expression levels of 56 miRNAs were altered in SRBSDV-infected rice plants, with these changes classified into eight different regulation patterns according to their temporal expression dynamics. Fourteen miRNAs belonging to six families (miR164, R396, R530, R1846, R1858, and R2097) were significantly regulated at 20 dpi. We used RT-qPCR to search for expression level correlations between members of these families and their putative targets at 3, 9, and 15 dpi. Some members of the miR164, R396, R530, and R1846 families were found to be positively or negatively correlated with their respective targets during 3-15 days after SRBSDV infection, whereas in more cases the rice miRNAs were not in correlation with their targets along the post-inoculation period, suggesting that some additional factors may be involved in rice miRNA-target interactions. The reported functions of rice genes targeted by the miR164, R396, R530, R1846, and R1858 families indicated that these genes are associated with symptom development. These results provide insights into miRNA-mediated SRBSDV-rice interactions.

A celery isolate of Apium virus Y (ApVY-Ce) from diseased plants in a commercial field in California was characterized. The experimental host range of the virus included 13 plant species in the families Apiaceae , Chenopodiaceae and Solanaceae . Almost all infected plant species showed foliar chlorosis and distortion or severe stunting and systemic chlorosis. ApVY-Ce was transmitted to all 10 host species in the Apiaceae by green peach aphids. It reacted with the potyvirus group antibody and Celery mosaic virus (CeMV) antiserum. The complete genomic sequence of ApVY-Ce was determined to be 9917 nucleotides, excluding the 3′ poly(A) tail, and it comprises a large open reading frame encoding a polyprotein of 3184 amino acid residues. Its genomic organization is typical of potyviruses, and contains conserved motifs found in the genus Potyvirus . Comparisons with available genomic sequences of other potyviruses indicate that ApVY-Ce shares 26.1–52.9% identities with species of the existing genera and unassigned viruses in the Potyviridae at the polyprotein sequence level. Extensive phylogenetic analysis based on the 3′-partial sequences confirms that ApVY-Ce is most closely related to CeMV and is a distinct species of the genus Potyvirus .