Tobacco Nectarin III is a Bifunctional Enzyme with Monodehydroascorbate Reductase and Carbonic Anhydrase Activities

Tobacco Nectarin III is a Bifunctional Enzyme with Monodehydroascorbate Reductase and Carbonic... Tobacco plants secrete a limited array of proteins (nectarins) into their floral nectar. N-terminal sequencing of the Nectarin II (NEC2; 35kD) and the Nectarin III (NEC3; 40kD) proteins revealed that they both share identity with dioscorin, the major soluble protein of yam tubers. These sequences also revealed that NEC2 is a breakdown product of NEC3. Using these N-terminal peptide sequences, degenerate oligonucleotides were designed that permitted the isolation of a partial NEC3 cDNA. This cDNA was then used to probe a nectary specific cDNA library and a full-length NEC3 cDNA clone was isolated. Complete sequence analysis confirmed the identity of NEC3 as a dioscorin-like protein. MALDI-TOF mass spectrometric fingerprinting of tryptic peptides derived from the purified NEC3 confirmed that this protein was encoded by the isolated cDNA. NEC3 was shown to possess both carbonic anhydrase and monodehydroascorbate reductase activities. RT-PCR based expression analyses demonstrated that NEC3 transcript is expressed throughout nectary development as well as in other floral organs. A proposed function in the maintenance of pH and oxidative balance in nectar is discussed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Molecular Biology Springer Journals

Tobacco Nectarin III is a Bifunctional Enzyme with Monodehydroascorbate Reductase and Carbonic Anhydrase Activities

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Publisher
Kluwer Academic Publishers
Copyright
Copyright © 2004 by Kluwer Academic Publishers
Subject
Life Sciences; Biochemistry, general; Plant Sciences; Plant Pathology
ISSN
0167-4412
eISSN
1573-5028
D.O.I.
10.1023/B:PLAN.0000036373.84579.13
Publisher site
See Article on Publisher Site

Abstract

Tobacco plants secrete a limited array of proteins (nectarins) into their floral nectar. N-terminal sequencing of the Nectarin II (NEC2; 35kD) and the Nectarin III (NEC3; 40kD) proteins revealed that they both share identity with dioscorin, the major soluble protein of yam tubers. These sequences also revealed that NEC2 is a breakdown product of NEC3. Using these N-terminal peptide sequences, degenerate oligonucleotides were designed that permitted the isolation of a partial NEC3 cDNA. This cDNA was then used to probe a nectary specific cDNA library and a full-length NEC3 cDNA clone was isolated. Complete sequence analysis confirmed the identity of NEC3 as a dioscorin-like protein. MALDI-TOF mass spectrometric fingerprinting of tryptic peptides derived from the purified NEC3 confirmed that this protein was encoded by the isolated cDNA. NEC3 was shown to possess both carbonic anhydrase and monodehydroascorbate reductase activities. RT-PCR based expression analyses demonstrated that NEC3 transcript is expressed throughout nectary development as well as in other floral organs. A proposed function in the maintenance of pH and oxidative balance in nectar is discussed.

Journal

Plant Molecular BiologySpringer Journals

Published: Oct 10, 2004

References

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