Inducing bract-like leaves in Arabidopsis through ectopically expressing an ASR gene from the dove tree

Abstract

Bract, or inflorescence leaf, is cryptic in most model plants due to a conserved suppression mechanism. While, bract is present in some ornamental plants and plays an important role in their reproductive growth. The huge and long-standing bract of an ancient species, the dove tree (Davidia), implies the existence of a distinctive pathway of bract development. However, compared to bract suppression, little is known about the regulators during bract promoting. Here, a gene named DiASR1 involved into bract development regulation in Davidia is reported. During bract development, the expression profile of the DiASR1 gene was bract-specific, and increased along with the bract growth. The DiASR1 gene was activated by environmental cues including high temperature, strong light and abscisic acid, while inhibited by low temperature, dark, gibberellin. Remarkably, ectopic expression of the DiASR1 gene resulted in bract-like leaves, besides early flowering, abnormal floral development, and aborted pollens in transgenic Arabidopsis lines. The bract-like Arabidopsis leaves exhibited a similar fading process and cell architecture to those of Davidia bract. The ectopic induction of bract-like leaves confirmed the critical function of the DiASR1 gene for bract development, and provided new insights to understand the regulation mechanism underlying the process of leaf metamorphosis.