Briddon Rob W, Bull Simon E, Amin Imran, Idris Ali M, Mansoor Shahid, Bedford Ian D, Dhawan Poonam, Rishi Narayan, Siwatch Surender S, Abdel-Salam Aly M, Brown Judith K, Zafar Yusuf, Markham Peter G
Department of Disease and Stress Biology, John Innes Centre, Colney Lane, Norwich, NR4 7UH, UK.
Virology. 2003 Jul 20;312(1):106-21. doi: 10.1016/s0042-6822(03)00200-9.
DNA beta molecules are symptom-modulating, single-stranded DNA satellites associated with monopartite begomoviruses (family Geminiviridae). Such molecules have thus far been shown to be associated with Ageratum yellow vein virus from Singapore and Cotton leaf curl Multan virus from Pakistan. Here, 26 additional DNA beta molecules, associated with diverse plant species obtained from different geographical locations, were cloned and sequenced. These molecules were shown to be widespread in the Old World, where monopartite begomoviruses are known to occur. Analysis of the sequences revealed a highly conserved organization for DNA beta molecules consisting of a single conserved open reading frame, an adenine-rich region, and a region of high sequence conservation [the satellite conserved region (SCR)]. The SCR contains a potential hairpin structure with the loop sequence TAA/GTATTAC; similar to the origins of replication of geminiviruses and nanoviruses. Two major groups of DNA beta satellites were resolved by phylogenetic analyses. One group originated from hosts within the Malvaceae and the second from a more diverse group of plants within the Solanaceae and Compositae. Within the two clusters, DNA beta molecules showed relatedness based both on host and geographic origin. These findings strongly support coadaptation of DNA beta molecules with their respective helper begomoviruses.
DNAβ分子是与单组分双生病毒（双生病毒科）相关的症状调节性单链DNA卫星分子。迄今为止，此类分子已被证明与来自新加坡的藿香蓟黄脉病毒以及来自巴基斯坦的棉花曲叶木尔坦病毒有关。在此，克隆并测序了另外26个与来自不同地理位置的多种植物物种相关的DNAβ分子。这些分子在已知存在单组分双生病毒的旧大陆广泛分布。序列分析揭示了DNAβ分子高度保守的结构，其由一个单一的保守开放阅读框、一个富含腺嘌呤的区域以及一个高度序列保守区域[卫星保守区域（SCR）]组成。SCR包含一个潜在的发夹结构，其环序列为TAA/GTATTAC；类似于双生病毒和纳米病毒的复制起点。通过系统发育分析解析出了两大类DNAβ卫星分子。一类起源于锦葵科植物宿主，另一类起源于茄科和菊科中更为多样的植物类群。在这两个聚类中，DNAβ分子基于宿主和地理起源显示出相关性。这些发现有力地支持了DNAβ分子与其各自的辅助双生病毒的共同适应。
