Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering, Faisalabad, Pakistan.
Virus Res. 2010 Sep;152(1-2):153-63. doi: 10.1016/j.virusres.2010.06.019. Epub 2010 Jun 26.
Cotton leaf curl disease (CLCuD) is the major limitation to cotton production across Pakistan and northwestern India. The disease first appeared in epidemic form in the 1980s and was shown to be caused by monopartite begomoviruses (seven distinct species have thus far been shown to be involved), frequently as multiple infections. Additionally, the viruses are associated with a specific satellite, the CLCuD betasatellite Cotton leaf curl Multan betasatellite (CLCuMB), which is responsible for the distinctive disease symptoms, and a satellite-like molecule (termed an alphasatellite), the function of which is unclear. During the late 1990s, cotton varieties with conventional resistance were introduced, alleviating losses to cotton production. However, during 2001 a resistance breaking strain of CLCuD (known as the "Burewala" strain) appeared which spread across most cotton producing areas of Pakistan. We have conducted an analysis of the Burewala strain and show that, contrary to the earlier (Multan) strain, it consists of a single begomovirus. The virus is associated with a recombinant betasatellite, derived from the Multan strain, but we were unable to detect the presence of an alphasatellite. Sequence comparisons show the virus to be a new recombinant species, consisting of sequences derived from two of the viruses associated with the first epidemic, for which we propose the name Cotton leaf curl Burewala virus (CLCuBuV). Surprisingly the virus lacks an intact C2 gene, encoding the transcriptional activator protein, which is invariably present in begomoviruses. The possible mechanisms for the selection of a "defective" begomovirus are discussed.
棉花曲叶病（CLCuD）是巴基斯坦和印度西北部棉花生产的主要限制因素。这种疾病在 20 世纪 80 年代首次以流行形式出现，被证明是由单分体伴生病毒引起的（迄今为止已显示有七种不同的物种参与），通常是多重感染。此外，这些病毒与一种特定的卫星（称为 CLCuD betasatellite Cotton leaf curl Multan betasatellite，即 CLCuMB）相关联，该卫星负责独特的疾病症状，以及一种类似卫星的分子（称为 alphasatellite），其功能尚不清楚。在 20 世纪 90 年代末，引入了具有常规抗性的棉花品种，缓解了棉花生产的损失。然而，在 2001 年，一种抗断裂的 CLCuD 菌株（称为“Burewala”菌株）出现，并在巴基斯坦大部分棉花种植区传播。我们对 Burewala 菌株进行了分析，结果表明，与早期（Multan）菌株不同，它只由一种单分体伴生病毒组成。该病毒与一种重组的 betasatellite 相关联，该 betasatellite 源自 Multan 菌株，但我们未能检测到 alphasatellite 的存在。序列比较表明，该病毒是一种新的重组种，由与第一次流行相关的两种病毒的序列组成，我们建议将其命名为棉花曲叶病 Burewala 病毒（CLCuBuV）。令人惊讶的是，该病毒缺乏一个完整的 C2 基因，该基因编码转录激活蛋白，这在伴生病毒中是普遍存在的。我们讨论了选择“缺陷”伴生病毒的可能机制。
