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

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

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84 Scopus citations


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
Issue number2
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.


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


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