Coordination between growth and stress responses by DELLA in the liverwortMarchantia polymorpha

Summary Plant survival depends on the optimal use of resources under variable environmental conditions. Among the mechanisms that mediate the balance between growth, differentiation and stress responses, the regulation of transcriptional activity by DELLA proteins stands out. In angiosperms, DELLA accumulation promotes defense against biotic and abiotic stress and represses cell division and expansion, while loss of DELLA function is associated with increased plant size and sensitivity towards stress 1 . Given that DELLA protein stability is dependent on gibberellin (GA) levels 2 , and GA metabolism is influenced by the environment 3 , this pathway is proposed to relay environmental information to the transcriptional programs that regulate growth and stress responses in angiosperms 4,5 . However, DELLA genes are also found in bryophytes, whereas canonical GA receptors appeared only in vascular plants 6–10 . Thus, it is not clear whether these regulatory functions of DELLA predated or emerged with typical GA signaling. Here we show that, as in vascular plants, the only DELLA in the liverwort Marchantia polymorpha also participates in the regulation of growth and key developmental processes, and promotes the tolerance towards oxidative stress. Moreover, part of these effects is likely caused by the conserved physical interaction with the MpPIF transcription factor. Therefore, we suggest that the role in the coordination of growth and stress responses was already encoded in DELLA from the common ancestor of land plants, and the importance of this function is justified by its conservation over the past 450 M years.