Plant Molecular Biology

, Volume 41, Issue 2, pp 207–216

Nectarin I is a novel, soluble germin-like protein expressed in the nectar of Nicotiana sp.

  • Clay Carter
  • Richard A. Graham
  • Robert W. Thornburg
Article

DOI: 10.1023/A:1006363508648

Cite this article as:
Carter, C., Graham, R.A. & Thornburg, R.W. Plant Mol Biol (1999) 41: 207. doi:10.1023/A:1006363508648

Abstract

We have identified a limited number of proteins secreted into the nectar of tobacco plants. Nectarin I is the most highly expressed nectar protein and has a monomer molecular mass of 29 kDa. The other major nectar proteins are expressed at lower levels and have monomer molecular masses of 41, 54, and 65 kDa respectively. Nectarin I was purified and antiserum was raised against the protein. Under nondenaturing conditions, Nectarin I has an apparent molecular mass of >120 kDa. The expression of Nectarin I was restricted to nectary tissues and to a much lower level in the ovary. No Nectarin I was found in petals, stems, leaves, or roots or other floral tissues. The expression of Nectarin I was also developmentally regulated. It is expressed in nectary tissues only while nectar is being actively secreted. Subsequently, the N-terminus of purified Nectarin I was sequenced. Sequence identity showed Nectarin I is related to wheat germin. Although hydrogen peroxide is readily detectable in tobacco floral nectar, we were unable to demonstrate any oxalate oxidase activity for Nectarin I. A partial cDNA encoding the mature Nectarin I N-terminus was isolated and used to probe a Nicotiana plumbaginifolia genomic library. The Nectarin I gene was isolated and the translated sequence was consistent with both N-terminal and internal cyanogen bromide-derived amino acid sequence. The gene contains a single 386 nt intron and encodes a mature protein of 197 amino acids.

germin germin-like proteins nectar Nicotiana oxalate oxidase 

Copyright information

© Kluwer Academic Publishers 1999

Authors and Affiliations

  • Clay Carter
    • 1
  • Richard A. Graham
    • 1
  • Robert W. Thornburg
    • 1
  1. 1.Department of Biochemistry and BiophysicsIowa State UniversityAmesUSA

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