Caulimoviridae

Caulimoviridae

Diagram of the Cauliflower mosaic virus RNA structure

Caulimoviridae is a family of viruses known as the plant pararetroviruses. These viruses are characterized by their double-stranded DNA genomes and their ability to replicate through an RNA intermediate, similar to the retrovirus replication cycle. Members of this family are known to infect a wide range of plant species, causing various plant diseases that can have significant agricultural impacts.

Structure

The virions of Caulimoviridae are non-enveloped and have an icosahedral symmetry. The capsid is composed of a single type of protein and encloses the double-stranded DNA genome. The genome is circular and ranges from 7.5 to 8.0 kilobases in length. The replication of these viruses involves reverse transcription, a process that is also utilized by retroviruses.

Genome

The genome of Caulimoviridae is organized into several open reading frames (ORFs) that encode proteins necessary for the virus's replication and assembly. One of the most studied members of this family is the Cauliflower mosaic virus (CaMV), which has a well-characterized genome. The CaMV genome includes a promoter known as the 35S promoter, which is widely used in genetic engineering of plants due to its strong and constitutive expression in plant cells.

Life Cycle

The life cycle of Caulimoviridae involves both nuclear and cytoplasmic phases. The virus enters the plant cell and releases its DNA into the nucleus, where it is transcribed into RNA. This RNA serves as a template for reverse transcription, producing new viral DNA genomes. These genomes are then packaged into new virions, which can spread to other cells and plants.

Transmission

Caulimoviridae are primarily transmitted by insect vectors, such as aphids and leafhoppers, in a non-circulative manner. This means that the virus does not replicate within the insect vector but is carried on the surface of the insect's mouthparts. The virus can also be transmitted through mechanical means, such as contaminated tools or by grafting.

Economic Impact

Infections by Caulimoviridae can lead to significant crop losses, affecting the yield and quality of important agricultural products. The symptoms of infection can include mosaic patterns on leaves, stunted growth, and reduced fruit production. Effective management of these viruses involves controlling the insect vectors and using resistant plant varieties.

Related Pages

• Virus
• Retrovirus
• Plant pathology
• Genetic engineering
• Cauliflower mosaic virus