PULLMAN, Wash. — A recent, fundamental discovery about communication within plants, made by a research group that includes Washington State University botany professor Vincent Franceschi, is featured in the January 1999 issue of Science magazine.
Franceschi, in collaboration with a group led by his colleague William Lucas of the University of California, Davis, helped solve part of the mystery of how plants are able to move large, messenger molecules from adjacent cells into phloem tubes through tiny holes called plasmodesmata in the phloem walls. Phloem tubes carry nutrients and information to and from distant plant parts. Growing shoots of a plant, for instance, get information from the leaves about day length that triggers the switch from making leaves to growing flowers instead.
The research team identified a “movement protein” that temporarily increases the size exclusion limit of the plasmodesmata holes in the phloem walls so that certain large molecules can move through. It was known that viruses use movement proteins to spread infection to other parts of plants, but this is the first time a movement protein coded by the plant itself has been found. Earlier work in 1997 by Franceschi and colleagues in Germany, also published in Science, indicated that proteins and mRNA did move into phloem cells, but this latest research is the first to suggest the mechanism by which it happens.
The initial high-resolution electron microscope imaging that showed the localization of these molecules in the phloem was done at the WSU Electron Microscopy Center. Franceschi, director of the EMC, said, “The combination of molecular biology and new cell imaging techniques, and now being able to work with living cells, has resulted in an explosion of knowledge. It’s just incredible.”
Franceschi has an international reputation for his work in the cell biology of transport, including phloem transport. He is a member of the American Association for the Advancement of Science, and has been on the WSU faculty since 1982.
Science magazine, the nation’s leading science journal, is published by the AAAS.

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