A subclass of plant heat shock cognate 70 chaperones carries a motif that facilitates trafficking through plasmodesmata.
Plasmodesmata establish a pathway for the trafficking of non-cell-autonomously acting proteins and ribonucleoprotein complexes. Plasmodesmal enriched cell fractions and the contents of enucleate sieve elements, in the form of phloem sap, were used to isolate and characterize heat shock cognate 70 (Hsc70) chaperones associated with this cell-to-cell transport pathway. Three Cucurbita maxima Hsc70 chaperones were cloned and functional and sequence analysis led to the identification of a previously uncharacterized subclass of non-cell-autonomous chaperones. The highly conserved nature of the heat shock protein 70 (Hsp70) family, in conjunction with mutant analysis, permitted the characterization of a motif that allows these Hsc70 chaperones to engage the plasmodesmal non-cell-autonomous translocation machinery. Proof of concept that this motif is necessary for Hsp70 gain-of-movement function was obtained through the engineering of a human Hsp70 that acquired the capacity to traffic through plasmodesmata. These results are discussed in terms of the roles likely played by this subclass of Hsc70 chaperones in the trafficking of non-cell-autonomous proteins.
Aoki
Koh
K
Section of Plant Biology, Division of Biological Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA.
Kragler
Friedrich
F
Xoconostle-Cazares
Beatriz
B
Lucas
William J
WJ
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002473:Cell Wall / Q000378:metabolism*; D028464:Cucurbita / Q000235:genetics*; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000145:classification / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D005810:Multigene Family; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000145:classification / Q000502:physiology*; D031425:Plasmodesmata / Q000378:metabolism*; D015202:Protein Engineering; D020033:Protein Isoforms / Q000737:chemistry / Q000502:physiology; D021381:Protein Transport / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014026:Nicotiana / Q000235:genetics*; D014170:Transformation, Genetic; D014178:Translocation, Genetic
D018840:HSP70 Heat-Shock Proteins; D010446:Peptide Fragments; D010940:Plant Proteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins