Basic LEUCINE ZIPPER TRANSCRIPTION FACTOR 67 transactivates DELAY OF GERMINATION 1 to establish primary seed dormancy in Arabidopsis.

Seed dormancy governs the timing of germination; one of the most important developmental transitions in a plant's life cycle. The DELAY OF GERMINATION 1 (DOG1) gene is a key regulator of seed dormancy and a major quantitative trait locus in Arabidopsis thaliana. DOG1 expression is under tight developmental and environmental regulation, but the transcription factors involved are not known. Here we show that basic LEUCINE ZIPPER TRANSCRIPTION FACTOR 67 (bZIP67) acts downstream of the central regulator of seed development LEAFY COTYLEDON 1 to transactivate DOG1 during maturation and help to establish primary dormancy. We show that bZIP67 overexpression enhances dormancy and bZIP67 protein (but not transcript) abundance is increased in seeds matured in cool conditions, providing a mechanism to explain how temperature regulates DOG1 expression. We also show that natural allelic variation in the DOG1 promoter affects bZIP67-dependent transactivation, providing a mechanism to explain ecotypic differences in seed dormancy that are controlled by the DOG1 locus.