Association of six YFP-myosin XI-tail fusions with mobile plant cell organelles

We investigated 6 of the 13 class XI Arabidopsis myosins. cDNAs corresponding to the tail region of 6 myosin genes were generated and incorporated into a vector to encode YFP-myosin tail fusion proteins lacking the motor domain. Chimeric genes incorporating tail regions of myosin XI-5 (At MYA1), myosin XI-6 (At MYA2), myosin XI-8 (At XI-B), myosin XI-15 (At XI-I), myosin XI-16 (At XI-J) and myosin XI-17 (At XI-K) were expressed transiently. All YFP-myosin-tail fusion proteins were targeted to small organelles ranging in size from 0.5 to 3.0 μm. Despite the absence of a motor domain, the fluorescently-labeled organelles were motile in most cells. Tail cropping experiments demonstrated that the coiled-coil region was required for specific localization and shorter tail regions were inadequate for targeting. Myosin XI-6 (At MYA2), previously reported to localize to peroxisomes by immunofluorescence, labeled both peroxisomes and vesicles when expressed as a YFP-tail fusion. None of the 6 YFP-myosin tail fusions interacted with chloroplasts, and only one YFP-tail fusion appeared to sometimes co-localize with fluorescent proteins targeted to Golgi and mitochondria.6 myosin XI tails, extending from the coiled-coil region to the C-terminus, label specific vesicles and/or organelles when transiently expressed as YFP fusions in plant cells. Although comparable constructs lacking the motor domain result in a dominant negative effect on organelle motility in animal systems, the plant organelles remained motile. YFP-myosin tail fusions provide specific labeling for vesicles of unknown composition, whose identity can be investigated in future studies.Intracellular motility of organelles and transport vesicles is critical for optimization of photosynthesis and metabolism. The dynamic nature of mitochondria [1,2], chloroplasts [3], non-green plastids [4], peroxisomes [5,6], and Golgi bodies [7] has been documented through chlorophyll or fluorescent protein labeling of the organelles