In plants, high temperatures induce thermo-morphogenesis, which reprograms growth and development. In their latest study, Sibum Sung and colleagues investigate the role of VIL1, a Polycomb-associated protein required for regulating the response to cold temperatures (vernalisation), in heat adaptation. The authors show that, unlike wild-type Arabidopsis, vil1 mutants do not exhibit heat responses, such as accelerated flowering, when grown at 27°C rather than 22°C. Using transcriptomic and epigenetic profiling, they reveal that VIL1 localises at temperature-responsive loci and is required for Histone 3 lysine 27 trimethylation (H3K27me3) accumulation at high temperatures. In addition, the researchers compare the phenotypes of vil1 and arp6 mutants, in which thermo-morphogenesis is constitutively active. They reveal that loss of VIL1 function suppresses the arp6 mutant phenotype and these two proteins antagonistically regulate a shared pool of differentially expressed genes, with arp6vil1 double mutants exhibiting a wild-type-like transcriptome. Furthermore, ARP6 is required for the deposition of H2A.Z, which is evicted from temperature-sensitive loci at high temperatures. The authors determine that VIL1 indirectly regulates H2A.Z eviction specifically at high temperatures and independently of its function in H3K27me3. Together, these data provide new mechanistic insight in thermo-morphogenesis, with implications for climate change.
