Structure and Sequence Analyses of the Determinants Required for Satellite RNA-mediated Interference with Bamboo Mosaic Virus Replication

• Main Authors: Hsin-Chuan Chen, 陳信全
• Other Authors: Na-Sheng Lin
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/76761148855597671973

博士 === 國防醫學院 === 生命科學研究所 === 95 === Satellite RNAs associated with Bamboo mosaic virus (satBaMV) are subviral agents depending on BaMV for replication, encapsidation and systemic movement. Natural satBaMV isolates can be categorized into 2 major phylogenetic groups. A hypervariable (HV) region with divergence of up to 20% in the 5’ untranslated region (UTR) of satBaMV isolates, folds into a conserved apical hairpin stem loop (AHSL) structure containing an apical loop and 2 internal loops. Among the satBaMV isolates, BSL6 reduces the accumulation of BaMV RNAs and attenuates the BaMV-induced symptoms in co-inoculated plants, whereas BSF4 does not. The determinants of the downregulation of BaMV replication were mapped to the 5’ UTR of BSL6. In this study, we confirmed the predicted secondary structure of BSL6 5’ UTR by enzymatic probing and demonstrated that the major determinants of satellite RNA-mediated interference were in the HV region. The integrity of the AHSL structure of interfering satBaMV was essential for the interference of BaMV accumulation. Concurrent analyses of natural satBaMV isolates revealed that all of the interfering isolates contained the same structures and sequences in the internal loops. Refined analyses indicated that, besides the AHSL structure, C60 and 81UGC83 in the internal loops play a crucial role in the downregulation. Given that interfering satBaMV is more competent than noninterfering satBaMV and BaMV during replication, and the 5’ end of BaMVs harboring satBaMV co-evolved the AHSL-like structure with satBaMV, we propose that the 5’ AHSL of BSL6 may be a potent determinant for recruiting the limited quantities of cellular and/or viral factors required for the replication of BaMV and satBaMV. Moreover, the downregulation event by satBaMV was not affected by a viral gene-silencing suppressor inserted into BaMV or satBaMV RNA.