Publication Type: | Journal Article |
Year of Publication: | 2010 |
Authors: | Iven, T, Strathmann, A, Böttner, S, Zwafink, T, Heinekamp, T, Guivarc’h, A, Roitsch, T, Dröge-Laser, W |
Journal: | The Plant Journal |
Volume: | 63 |
Issue: | 1 |
Date Published: | 2010 |
ISBN Number: | 1365-313X |
Keywords: | auxin, bZIP transcription factors, invertase, Nicotiana, Nicotiana tabacum, NIN88, pollen development, tobacco |
Abstract: | Expression of BZI-1ΔN, a dominant-negative form of the tobacco (Nicotiana tabacum) basic leucine zipper (bZIP) transcription factor BZI-1 leads to severe defects in pollen development which coincides with reduced transcript abundance of the stamen specific invertase gene NIN88 and decreased extracellular invertase enzymatic activity. This finding suggests a function of BZI-1 in regulating carbohydrate supply of the developing pollen. BZI-1 heterodimerises with the bZIP factors BZI-2, BZI-3 and BZI-4 in vitro and in planta. Whereas BZI-1 exhibits only weak activation properties, BZI-1/BZI-2 heterodimers strongly activate transcription. Consistently, approaches leading to reduced levels of functional BZI-1 or BZI-2 both significantly interfere with pollen development, auxin responsiveness and carbohydrate partitioning. In situ hybridisation studies for BZI-1 and BZI-2 confirmed temporal and spatial overlapping expression patterns in tapetum and pollen supporting functional cooperation of these factors during pollen development. Plants over-expressing BZI-4 produce significantly reduced amounts of intact pollen and are also impaired in NIN88 transcription and enzymatic activity. BZI-4 homodimer efficiently binds to a G-box located in the NIN88 promoter but exhibits almost no transcriptional activation capacity. As BZI-4 does not actively repress transcription, we propose that its homodimer blocks G-box mediated transcription. In summary, these data support a regulatory model in which BZI-4 homodimers and BZI-1/BZI-2 heterodimers perform opposing functions as negative or positive transcriptional regulators during pollen development. |
URL: | http://dx.doi.org/10.1111/j.1365-313X.2010.04230.x |
Short Title: | The Plant Journal |
Homo- and heterodimers of tobacco bZIP proteins counteract as positive or negative regulators of transcription during pollen development
Taxonomic name: