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A small anaerobically induced tomato transcription factor was isolated from a subtractive library. This factor, desig-nated ABZ1 (anaerobic basic leucine zipper), is anaerobi-cally induced in fruits, leaves and roots and encodes a nuclear localized protein. ABZ1 shares close structural and sequence homology with the S-family of small basic leucine zipper (bZIP) transcription factors that are implicated in stress response.Nuclear localizationofABZ1 ismediatedby the basic region and occurs under normoxic conditions. ABZ1 binds to G-box-like target sites as a dimer. . | Eur. J. Biochem. 271 4534-4544 2004 FEBS 2004 doi 10.1111 j.1432-1033.2004.04413.x Functional dissection of a small anaerobically induced bZIP transcription factor from tomato Simone Sell and Reinhard Hehl Institut fur Genetik Technische Universitat Braunschweig Germany A small anaerobically induced tomato transcription factor was isolated from a subtractive library. This factor designated ABZ1 anaerobic basic leucine zipper is anaerobically induced in fruits leaves and roots and encodes a nuclear localized protein. ABZ1 shares close structural and sequence homology with the S-family of small basic leucine zipper bZIP transcription factors that are implicated in stress response. Nuclear localization of ABZ1 is mediated by the basic region and occurs under normoxic conditions. ABZ1 binds to G-box-like target sites as a dimer. Binding can be abolished by heterodimerization with a truncated protein retaining the leucine zipper but lacking the DNA binding domain. The protein binds in a sequence specific manner to the CaMV 35S promoter which is down regulated when ABZ1 is coexpressed. This correlates with the anaerobic down regulation of the 35S promoter in tomato and tobacco. These results may suggest that small bZIP proteins are involved in the negative regulation of gene expression under anaerobic conditions. Keywords anaerobiosis bZIP DNA binding Lycopersicon esculentum transcription factor. Plant survival under adverse environmental situations is largely dependent on their adaptation strategies. Anaero-biosis or low oxygen conditions occur when plants are subjected to flooding or to waterlogging of the soil. Under these conditions oxygen is rapidly consumed by microorganisms and plant roots 1 . Plants react to these conditions with a variety of responses. To compensate the decrease in energy production and the lack of NADH regeneration the rate of glycolysis is increased and fermentative pathways are induced 1 . Furthermore plants can respond to flooding with the .
