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

Clay Carter, Richard A. Graham, Robert W. Thornburg

Research output: Contribution to journalArticlepeer-review

77 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)207-216
Number of pages10
JournalPlant molecular biology
Volume41
Issue number2
DOIs
StatePublished - Sep 1999

Bibliographical note

Funding Information:
This work was sponsored by funds from the Carver Trust, the Hatch Act, and State of Iowa funds. The authors would like to thank Ms Michelle Ward for technical assistance.

Keywords

  • Germin
  • Germin-like proteins
  • Nectar
  • Nicotiana
  • Oxalate oxidase

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