Pumpkin phloem lectin genes are specifically expressed in companion cells

Dwight E. Bostwick, Joanne M. Dannenhoffer, Megan I. Skaggs, Richard M. Lister, Brian A. Larkins, Gary A. Thompson

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130 Scopus citations

Abstract

Pumpkin phloem exudate contains two abundant phloem proteins: PP1 is a 96-kD protein that forms polymeric filaments in vivo, and PP2 is a 48-kD dimeric lectin. Polyclonal antibodies raised against pumpkin phloem exudate were used to isolate several cDNAs corresponding to PP1 and PP2. RNA gel blot analysis indicated that PP1 is encoded by an mRNA of ∼2500 nucleotides, whereas PP2 subunits are encoded by an mRNA of 1000 nucleotides. Sequence analysis of PP2 cDNAs revealed a 654-bp open reading frame encoding a 218-amino acid polypeptide; this polypeptide had the carbohydrate binding characteristics of a PP2 subunit. The PP2 mRNA was localized within the phloem of pumpkin hypocotyl cross-sections based on in situ hybridization of a digoxigenin-labeled antisense probe. PP2 mRNA was found within the companion cells in both the bicollateral vascular bundles and the extrafascicular phloem network.

Original languageEnglish (US)
Pages (from-to)1539-1548
Number of pages10
JournalPlant Cell
Volume4
Issue number12
DOIs
StatePublished - Dec 1992

All Science Journal Classification (ASJC) codes

  • Plant Science
  • Cell Biology

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