A Geminivirus Replication Protein Interacts with a Protein Kinase and a Motor Protein That Display Different Expression Patterns during Plant Development and Infection

Abstract

The geminivirus protein AL1 initiates viral DNA replication, regulates its own expression, and induces plant gene transcription. To better understand how AL1 interacts with host proteins during these processes, we used yeast two-hybrid library screening and a baculovirus protein interaction system to identify plant proteins that interact with AL1. These studies identified a Ser/Thr kinase, a kinesin, and histone H3 as AL1 partners. The kinase is autophosphorylated and can phosphorylate common kinase substrates in vitro. The kinesin is phosphorylated in insect cells by a cyclin-dependent kinase. Immunostaining of Nicotiana benthamiana and Arabidopsis showed that kinase protein levels and subcellular location are regulated during plant development and geminivirus infection. By contrast, the kinesin is ubiquitous even though it is associated with the spindle apparatus in mitotic cells. Together, our results establish that AL1 interacts with host proteins involved in plant cell division and development. Possible functions of these host factors in healthy and geminivirus-infected plants are discussed.

ArabidopsisRETINOBLASTOMA-RELATED Is Required for Stem Cell Maintenance, Cell Differentiation, and Lateral Organ Production

“…In analogy to the better understood interactions between animal viruses and pRB (Felsani et al, 2006), it is likely that expression of plant viral proteins, which can interact with RBR (Kong and Hanley-Bowdoin, 2002), may interfere with RBR functions specific for cell cycle regulation or regulation of DNA replication. On the other hand, E2F/DP overexpression was associated with a strong increase in RBR expression (De Veylder et al, 2002) and might lead to enhanced E2F/DP-independent RBR functions.…”

Geminivirus Infection Up-Regulates the Expression of Two Arabidopsis Protein Kinases Related to Yeast SNF1- and Mammalian AMPK-Activating Kinases

“…AL1 and AL3 recruit host replication machinery by binding to PCNA and RFC, the clamp and clamp loader of the host DNA polymerase d (Luque et al, 2002;Castillo et al, 2003;Bagewadi et al, 2004). AL1 binding to a mitotic kinesin and histone H3 may also play a direct role in viral replication (Kong and Hanley-Bowdoin, 2002). The ability of AL3 to enhance viral DNA replication is mediated in part through its interaction with a host NAC1 transcription factor (Selth et al, 2005).…”

A single amino acid change in a geminiviral Rep protein differentiates between triggering a plant defence response and initiating viral DNA replication

“…This process is mainly mediated by Rep (Ach et al, 1997;Egelkrout et al, 2001;Kong et al, 2000;Nagar et al, 1995). Moreover, efficient viral DNA replication also depends on interactions between Rep and the virus-encoded replication-enhancing protein and coat protein (Malik et al, 2005;Settlage et al, 2005), as well as with several other host factors (Bagewadi et al, 2004;Castillo et al, 2003;Kong & Hanley-Bowdoin, 2002;Luque et al, 2002;Settlage et al, 2001;Singh et al, 2007;Xie et al, 1999Xie et al, , 1995. Second, Rep of ACMV and related begomoviruses can elicit HR (Hong et al, 2003;Selth et al, 2004;van Wezel et al, 2002a).…”