|
|
||||||||
|
Characterization and Immunolocalization of a Cytosolic Calcium-Binding Protein from Brassica napus and Arabidopsis Pollen1
Department of Molecular Biology and Genetics (K.R., L.J., S.J.R.) and Department of Botany (J.G.), University of Guelph, Guelph, Ontario, Canada N1G 2W1; University of Guelph, Guelph, Ontario, Canada N1G 2W1Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Road, Saskatoon, Saskatchewan, Canada S7N 0W9 (R.Z., T.H., S.M.H.); and Glaxo Research Laboratories, 5 Moore Drive, Research Triangle Park, North Carolina 27709 (W.E.B.) Two low-molecular-weight proteins have been purified from Brassica napus pollen and a gene corresponding to one of them has been isolated. The gene encodes an 8.6-kD protein with two EF-hand calcium-binding motifs and is a member of a small gene family in B. napus. The protein is part of a family of pollen allergens recently identified in several evolutionarily distant dicot and monocot plants. Homologs have been detected in Arabidopsis, from which one gene has been cloned in this study, and in snapdragon (Antirrhinum majus), but not in tobacco (Nicotiana tabacum). Expression of the gene in B. napus was limited to male tissues and occurred during the pollen-maturation phase of anther development. Both the B. napus and Arabidopsis proteins interact with calcium, and the potential for a calcium-dependent conformational change was demonstrated. Given this affinity for calcium, the cloned genes were termed BPC1 and APC1 (B. napus and Arabidopsis pollen calcium-binding protein 1, respectively). Immunolocalization studies demonstrated that BPC1 is found in the cytosol of mature pollen. However, upon pollen hydration and germination, there is some apparent leakage of the protein to the pollen wall. BPC1 is also concentrated on or near the surface of the elongating pollen tube. The essential nature of calcium in pollen physiology, combined with the properties of BPC1 and its high evolutionary conservation suggests that this protein plays an important role in pollination by functioning as a calcium-sensitive signal molecule. 1 This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC) to S.J.R. K.L.R was supported by graduate scholarships from NSERC and by the Ontario Graduate Scholarship program. 2 Present address: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, Saskatchewan, Canada S7N 0X2. * Corresponding author; e-mail rozwadowskik{at}em.agr.ca; fax 1-306-956-7247.
Plant Physiol. (1999) 120: 787-798
This article has been cited by other articles:
|
|||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ASPB Publications | PLANT PHYSIOLOGY® | THE PLANT CELL | |
|---|---|---|---|