Comparative Analysis of the Begomovirus AL2 Protein and the Curtovirus C2 Protein

Abstract

Geminiviruses are a group of plant-infecting viruses that include the genera Begomovirus and Curtovirus. Although members of these two genera are similar in regards to their mechanisms of replication and encapsidation, they exhibit differences in movement as well as in transcriptional activation of late gene promoters. This study evaluated protein-protein interactions of the begomovirus AL2 protein and a curtovirus C2 protein using the yeast two-hybrid system. The AL2 proteins of TGMV, BGMV, and CabLCV were evaluated for their ability to self-interact, as well as to interact with heterologous AL2 proteins, and host proteins. The AL2 proteins tested were all shown to contain the ability to self-interact and to interact heterologously with one another. However, interactions between the AL2 proteins and the host proteins could not be assayed due to lack of expression of certain AL2 'bait' proteins. The BCTV C2 protein was also evaluated for self-interaction and interaction with the begomovirus AL2 proteins. Unlike AL2, C2 was not shown to contain the property of self-interaction and the preponderance of the evidence demonstrated that it also did not interact with AL2. However, the BCTV C2 protein was shown for the first time to possess transcriptional activation activity. In addition, self-interaction of TGMV AL2 was tested using a biochemical assay. However, technical problems prevented the detection of TGMV AL2 self-interaction using an immunocapture approach, although such self-interaction was observed using the yeast two-hybrid system.