Molecular Plant Advance Access originally published online on September 18, 2009
Molecular Plant 2009 2(6):1262-1272; doi:10.1093/mp/ssp078
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Myosin XI Is Required for Actin-Associated Movement of Plastid Stromules
a Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
b Present address: Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
c Present address: School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
1 To whom correspondence should be addressed. E-mail jcg2{at}cam.ac.uk, fax +44 1223 333953, tel. +44 1223 333925.
Stromules are highly dynamic stroma-filled tubules extending from the surface of plastids and occasionally interconnecting individual plastids, allowing the movement of complex biological molecules between the interconnected plastids. Experiments with inhibitors of cytoskeleton assembly have indicated the involvement of an actin-based system in stromule movement. However, the motor protein associated with the system had not been identified. Here, we present direct evidence that myosin XI is involved in the formation and movement of stromules in tobacco leaves. Application of 2,3-butanedione 2-monoxime, an inhibitor of myosin ATPase activity, resulted in the loss of stromules from tobacco leaf epidermal cells. Transient RNA interference of myosin XI in leaves of Nicotiana benthamiana also resulted in the loss of stromules from epidermal cells, without any effect on transcripts for actin or myosin VIII. Transient expression of a GFP-tagged myosin XI tail domain in tobacco leaf epidermal cells showed that the fusion protein localized to the chloroplast envelope, as well as to mitochondria and other organelles. Our findings identify myosin XI as a key protein involved in the formation and movement of stromules.
Key Words: Chloroplast biology cytoskeleton organelle biogenesis/function tobacco