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TY - JOUR AU - Carter, Clay AU - Graham, Richard A. AU - Thornburg, Robert W. PY - 1999 DA - 1999/09/01 TI - Nectarin I is a novel, soluble germin-like protein expressed in the nectar of Nicotiana sp. JO - Plant Molecular Biology SP - 207 EP - 216 VL - 41 IS - 2 AB - 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. SN - 1573-5028 UR - https://doi.org/10.1023/A:1006363508648 DO - 10.1023/A:1006363508648 ID - Carter1999 ER -