CAPSELLA RUBELLA TGA4, A BZIP TRANSCRIPTION FACTOR, CAUSES DELAYED FLOWERING IN ARABIDOPSIS THALIANA

Flowering time is usually regulated by many environmental factors and endogenous signals. TGA family members are bZIP transcription factors that bind to the octopine synthase element, which has been closely linked to defense/stress responses. Most TGA factors interact with non-expressor of PR1 (NPR1) and plant defense responses are strengthened by this interaction. TGA1 and TGA4 factors bind to NPR1 only in salicylic acid (SA)-induced leaves, suggesting that TGA4 has another function during plant development. Here, we isolated a bZIP transcription factor gene, TGA4, from Capsella rubella. TGA4 transcripts were detected in most tissues, with high expression in leaves, low expression in stems and flowering buds, and undetectable in siliques. CruTGA4 was overexpressed in Arabidopsis thaliana wild type Col-0 plants. Flowering time and total leaf number in the transgenic plants showed that overexpression of CruTGA4 could delay flowering in A. thaliana. Our findings suggest that TGA4 may act as flowering regulator that controls plant flowering.