Abstract
We previously reported that pumpkin phloem RNA-binding proteins, CmPP16-1 and CmPP16-2, have distinctive direction-selectivity in their long-distance movement (LDM) in the rice sieve tube. We are currently interested in elucidating the mechanisms controlling the selectivity. By using stylet-assisted introduction (MUSI) method, GFP was co-introduced with probe protein as an internal standard. Given that GFP represents the bulk flow transport, a comparative analysis of GFP and CmPP16s indicates that CmPP16 proteins are not just passively carried by the phloem bulk flow. Comparison of various CmPP16 preparations (with whole phloem proteins, purified native protein, or recombinant protein alone) implies the presence of *LDM factors* in the pumpkin phloem sap that help the selective LDM of CmPP16s, and the presence of amino acid sequence necessary for LDM. Analysis of arabidopsis expressing CmPP16s-GFP in the phloem implied that post-phloem movement is a part of control mechanisms of selective LDM.
