Effects of geminivirus infection on population dynamics, growth and photosynthesis of Eupatorium makinoi

Abstract

Viruses are one of the most important biotic stresses not only for cultivated plants, but also for wild plants. Recent advances in molecular biological techniques have clarified many aspects of viruses. However, only a few studies have been conducted about responses of host plants to viruses, especially for wild plants. I examined the responses of host plants to virus infection using the Eupatorium makinoi-geminivirus system to point out the importance of plant viruses in natural plant communities. Variegated E. makinoi plants caused by geminivirus infection are prevalent in fields in Japan. The natural population of E. makinoi plants rapidly declined after a virus epidemic to the state of near extinction for 8 years. Under controlled environments, inferior performances of virus-infected plants were attributed both to impaired photosynthesis and to a decrease in photosynthetic photon flux density which plants received. Photosynthetic properties of virus-infected leaves were characterized by a preferential loss of LHCII. The preferential loss of LHCII was caused by a decrease in the activity of chlorophyll synthesis. These studies demonstrated that geminivirus plays an important role in determining fitness of E. makinoi plants, which would underlie various ecological and evolutionary processes. It is necessary to link the studies on plant responses and those on viruses to understand the role of plant viruses in ecological and evolutionary processes in natural plant communities.