MADS1 maintains barley spike morphology at high ambient temperatures

Temperature stresses affect plant phenotypic diversity. The developmental stability of the inflorescence, required for reproductive success, is tightly regulated by the interplay of genetic and environmental factors. However, the mechanisms underpinning how plant inflorescence architecture responds to temperature are largely unknown. We demonstrate that the barley SEPALLATA MADS-box protein HvMADS1 is responsible for maintaining an unbranched spike architecture at high temperatures, while the loss-of-function mutant forms a branched inflorescence-like structure. HvMADS1 exhibits increased binding to target promoters via A-tract CArG-box motifs, which change conformation with temperature. Target genes for high-temperature-dependent HvMADS1 activation are predominantly associated with inflorescence differentiation and phytohormone signalling. HvMADS1 directly regulates the cytokinin-degrading enzyme HvCKX3 to integrate temperature response and cytokinin homeostasis, which is required to repress meristem cell cycle/division. Our findings reveal a mechanism by which genetic factors direct plant thermomorphogenesis, extending the recognized role of plant MADS-box proteins in floral development. In barley, a MADS transcription factor regulates inflorescence morphogenesis in response to warm temperature. MADS1 maintains unbranched spike morphology through repression of cell division in the spike meristem. A loss-of-function mutant forms branch-like spikes.

Automated summary

In response to temperature stress, a MADS transcription factor in barley regulates inflorescence morphology. HvMADS1 maintains unbranched spike morphology by repressing cell division in the spike meristem. A loss-of-function mutant results in the formation of branch-like spikes.