This paper originates from a presentation at the International Conference on Assimilate Transport and Partitioning, Newcastle, NSW, August 1999
Recent studies support the concept that long-distance signals are involved in
the regulation of resource allocation among the various plant organs.
Following the finding that viral movement proteins (MPs) can exert an effect
on sugar metabolism and resource allocation at sites distant from their
expression, we suggested that the MPs interfere with an element(s) involved in
the plant’s endogenous long-distance signal network. To provide
experimental support for this hypothesis, several unique procedures were
employed to identify interactions between viral MPs and phloem sap proteins
(PSPs) collected from cut petioles of squash
(Cucurbita pepo L. subsp. pepo)
and melon (Cucumis melo L.) plants. Far-western
experiments with blotted PSPs, using both bacteria-overexpressed and
in vitro-translated CMV- and TMV-MPs, revealed that the
two virally encoded proteins react specifically with more than one PSP.
Moreover, isolation of the naturally folded phloem protein in an affinity
column containing a TMV-MP-maltose-binding protein indicated, once again, an
interaction between the viral protein and similar PSPs. Two melon PSPs with
molecular masses of 8 and 23 kDa were found to specifically interact with both
the CMV- and TMV-MPs. The possible effects of this interaction in terms of
altering the process of phloem transport and resource allocation are
discussed.
Two Plant–Viral Movement Proteins Traffic in the Endocytic Recycling Pathway
