Evolutionary conservation of structure and function of the UVR8 photoreceptor from the liverwort Marchantia polymorpha and the moss Physcomitrella patens

Abstract

The ultraviolet-B (UV-B) photoreceptor UV RESISTANCE LOCUS 8 (UVR8) mediates photomorphogenic responses to UV-B in Arabidopsis through differential gene expression, but little is known about UVR8 in other species. Bryophyte lineages were the earliest diverging embryophytes, thus being the first plants facing the UV-B regime typical of land. We therefore examined whether liverwort and moss species have functional UVR8 proteins and whether they are regulated similarly to Arabidopsis UVR8. We examined the expression, dimer/monomer status, cellular localisation and function of Marchantia polymorpha and Physcomitrella patens UVR8 in experiments with bryophyte tissue and expression of green fluorescent protein (GFP)-UVR8 fusions in Nicotiana leaves and transgenic Arabidopsis. P. patens expresses two UVR8 genes that encode functional proteins, whereas the single M. polymorpha UVR8 gene expresses two transcripts by alternative splicing that encode functional UVR8 variants. P. patens UVR8 proteins form dimers that monomerise and accumulate in the nucleus following UV-B exposure, similar to Arabidopsis UVR8, but M. polymorpha UVR8 has weaker dimers and the proteins appear more constitutively nuclear. We conclude that liverwort and moss species produce functional UVR8 proteins. Although there are differences in expression and regulation of P. patens and M. polymorpha UVR8, the mechanism of UVR8 action is strongly conserved in evolution.

UVR8‐mediated induction of flavonoid biosynthesis for UVB tolerance is conserved between the liverwort Marchantia polymorpha and flowering plants

“…Both the P. patens and marchantia UVR8 sequences were able to functionally complement the Arabidopsis uvr8 mutant. However, while the P. patens UVR8 protein characteristics closely resembled those of Arabidopsis, marchantia UVR8 had notable differences (Soriano et al ., ). In contrast to Arabidopsis and P. patens , in marchantia dimeric UVR8 was barely detectable, and the monomer was present in both the cytoplasm and nucleus with or without UVB exposure.…”

“…The UVR8 protein sequence is strongly conserved in the plant lineage (Rizzini et al ., ; Fernández et al ., ; Soriano et al ., ), and UVR8 of the Chlorophyceae green alga Chlamydomonas reinhardtii shows conservation of action with Arabidopsis UVR8 (Allorent et al ., ; Tilbrook et al ., ). Recently, Soriano et al .…”

“…Recently, Soriano et al . () examined conservation of UVR8 structure and function in P. patens and the liverwort model species Marchantia polymorpha (hereafter, ‘marchantia’). Both the P. patens and marchantia UVR8 sequences were able to functionally complement the Arabidopsis uvr8 mutant.…”

“…Most research on UVR8 undertaken to date has been on Arabidopsis, and it is important to explore the function of UVR8 and the UVB response pathways in diverse plant species (Jenkins, 2017;Yin and Ulm, 2017). There is an increasing interest in the UVB responses of basal plants such as the bryophyte divisions, liverworts, hornworts and mosses Niemi et al, 2002;Clarke and Robinson, 2008;Newsham and Robinson, 2009;Wolf et al, 2010;Soriano et al, 2018). Not only do bryophytes dominate major climate change-vulnerable ecosystems such as those of the polar regions, but also as the proposed closest extant relatives of the first land plants they can provide information on characters of early evolutionary origin.…”

Pivotal roles of environmental sensing and signaling mechanisms in plant responses to climate change

“…Integration of different climate change-related cues can be greatly hampered by conflicting interferences, dysfunctional signaling, and inappropriate or maladaptive responses (Van Kleunen & Fischer, 2005), thus resulting in contrasted scenarios of enhanced acclimation or oversensitization to climate change (Bräutigam et al, 2013;Burggren, 2018;Duputié et al, 2015;Lande, 2009). The signaling capacities of plant species should therefore be assessed in light of their evolutionary history and of past planetary and climate conditions (Soriano et al, 2017). Signaling conflicts may be connected to evolutionary history of plant species and evolutionary dynamics of their signaling components (Schlichting, 2008).…”