<i>VERNALIZATION1</i> controls developmental responses of winter wheat under high ambient temperatures

Abstract

Low temperatures are required to regulate the transition from vegetative to reproductive growth via a pathway called vernalization. In wheat, vernalization predominantly involves the cold upregulation of the floral activator <i>VERNALIZATION1</i> (<i>VRN1</i>). Here, we have used an extreme vernalization response, identified through studying ambient temperature responses, to reveal the complexity of temperature inputs into <i>VRN-A1</i>, with allelic inter-copy variation at a gene expansion of <i>VRN-A1</i> modulating these effects. We find that the repressors of the reproductive transition, <i>VERNALIZATION2</i> (<i>VRN2</i>) and <i>ODDSOC2</i>, are re-activated when plants experience high temperatures during and after vernalization. In addition, this re-activation is regulated by photoperiod for <i>VRN2</i> but was independent of photoperiod for <i>ODDSOC2</i> We also find this warm temperature interruption affects flowering time and floret number and is stage specific. This research highlights the important balance between floral activators and repressors in coordinating the response of a plant to temperature, and that the absence of warmth is essential for the completion of vernalization. This knowledge can be used to develop agricultural germplasm with more predictable vernalization responses that will be more resilient to variable growth temperatures.