A histone H4 gene prevents premature bolting by attenuating
photoperiodic flowering genes under drought conditions in Chinese
cabbage
Abstract
Flowering is one of the most important traits in Chinese cabbage because
premature flowering reduces yield and quality of the harvested products.
Water deficit, caused by drought or other environmental conditions, can
induce early flowering. Drought resistance involves global reprogramming
of transcription, hormone signaling, and chromatin modification. How
these regulatory responses are coordinated via the various pathways is
largely unknown. We show that a histone H4 protein, BrHIS4.A04,
physically interacts with a homeodomain protein BrVIN3.1 that was
selected during the domestication of late-bolting Chinese cabbages.
Over-expression of BrHIS4.A04 resulted in drought hypersensitivity and
premature flowering under normal conditions but prevented premature
bolting under drought conditions. We show that the expression of key ABA
signaling genes (ABI1, MYC2, ABA1, and NCED3), and also photoperiodic
flowering genes (GI, FT, and SOC1) was attenuated by BrHIS4.A04 under
drought conditions. Furthermore, the level of H4-acetylation at these
gene loci was hampered in BrHIS4.A04OE plants. BrHIS4.A04 prevents
premature bolting by attenuating photoperiodic flowering genes under
drought conditions through the ABA signaling pathway. Since BrHIS4.A04OE
plants displayed no phenotypes related to vegetative or reproductive
development under drought, our findings will contribute to fine-tuning
of the flowering time in crops with no growth penalty through genetic
engineering.