Conserved and divergent roles of DELLA proteins in Physcomitrium (Physcomitrella) patens

DELLA proteins are master growth regulators that repress responses to the phytohormones gibberellins (GAs). Manipulation of DELLA signalling was instrumental in the development of high‐yielding crop varieties that saved millions from starvation during the “Green Revolution”. In order to infer how DELLA signalling has evolved within the land plant lineage, the functions of DELLA proteins in the bryophyte Physcomitrium (Physcomitrella) patens were examined in the present study. It was found that PpDELLAs are regulated differently from flowering DELLA proteins, as they are not degraded by diterpenes, they do not interact with GID1 homologues, they are not directly regulated by the 26S proteasome and they do not regulate abiotic stress responses. However, similarly to flowering plant DELLAs, they are involved in the regulation of reproductive development and they act as transcriptional ‘hubs’, possibly interacting with transcription factors belonging to similar families as flowering plant DELLA interactors. Using IP-MS and yeast two-hybrid, three photoreceptors were identified as PpDELLA protein-protein interactors, however no involvement of PpDELLAs in light responses was observed. In addition, while the Arabidopsis DELLA AtRGA1 did not interact with the seed dormancy regulator AtDOG1, PpDELLAs interacted with PpDOG1s, and the two proteins displayed similar functions in spore germination. This work shows that DELLA proteins in P. patens have both conserved and divergent functions. Unravelling how PpDELLAs function at the molecular level may provide novel ways of genetic modification that can be used to engineer better crops and contribute towards mitigating the effects of global warming and achieving global food security

Evolution of DELLA function and signaling in land plants

DELLA proteins are master growth regulators that repress responses to a group of plant growth hormones called gibberellins (GAs). Manipulation of DELLA function and signaling was instrumental in the development of high‐yielding crop varieties that saved millions from starvation during the “Green Revolution.” Despite decades of extensive research, it is still unclear how DELLA function and signaling mechanisms evolved within the land plant lineage. Here, we review current knowledge on DELLA protein function with reference to structure, posttranslational modifications, downstream transcriptional targets, and protein–protein interactions. Furthermore, we discuss older and recent findings regarding the evolution of DELLA signaling within the land plant lineage, with an emphasis on bryophytes, and identify future avenues of research that would enable us to shed more light on the evolution of DELLA signaling. Unraveling how DELLA function and signaling mechanisms have evolved could enable us to engineer better crops in an attempt to contribute to mitigating the effects of global warming and achieving global food security

The promiscuity of DELLA proteins was acquired during early land plant evolution

Trabajo presentado en el congreso EMBO Workshop An Integrated View of Land Plant Evolution, celebrado en el National Institute of Science Education and Research en Bhubaneswar (India) del 8 al 11 de noviembre de 2022DELLA proteins are land-plant speci%c transcriptional regulators that transduce environmental information to multiple processes throughout a plant’s life. The molecular basis for this critical function in angiosperms has been linked to the regulation of DELLA stability by gibberellins and to the capacity of DELLA proteins to interact with hundreds of transcription factors (TFs). However, it is not clear whether this promiscuity is an ancestral property of DELLA proteins or it is associated with their role in gibberellin signaling. We have found that representative DELLAs from the main plant lineages display a conserved ability to interact with multiple TFs. However, we have detected an extensive diversi%cation in the output target genes and biological processes regulated by these interactions, by comparing the DELLA-dependent transcriptomes across different land-plant lineages. We propose that promiscuity was already encoded in the ancestral DELLA protein, and that this molecular property has been largely maintained, while the lineage-dependent diversi%cation of DELLA- dependent biological functions mostly re#ects the functional evolution of their interacting partners

DELLA functions evolved by rewiring of associated transcriptional networks

DELLA proteins are land-plant specific transcriptional regulators that transduce environmental information to multiple processes throughout a plant’s life1–3. The molecular basis for this critical function in angiosperms has been linked to the regulation of DELLA stability by gibberellins and to the capacity of DELLA proteins to interact with hundreds of transcription factors4,5. Although bryophyte orthologues can partially fulfil functions attributed to angiosperm DELLA6,7, it is not clear whether the capacity to establish interaction networks is an ancestral property of DELLA proteins or is associated with their role in gibberellin signalling8–10. Here we show that representative DELLAs from the main plant lineages display a conserved ability to interact with multiple transcription factors. We propose that promiscuity was encoded in the ancestral DELLA protein, and that this property has been largely maintained, whereas the lineage-dependent diversification of DELLA-dependent functions mostly reflects the functional evolution of their interacting partners