Fernandez, M. B. | Search bioRxiv

bioRxiv2022

A bifunctional CPD/(6-4)- photolyase from the cyanobacteria Synechococcus sp. PCC 7335 constitutes an UV-B inducible operon: new insights into photolyases phylogenetic evolution

Photosynthetic organisms are continuously exposed to solar ultraviolet radiation-B (UV-B) because of their autotrophic lifestyle. UV-B provokes DNA damages, as cyclobutane pyrimidine dimers (CPD) or pyrimidine (6-4) pyrimidone photoproducts (6-4 PPs). The cryptochrome/ photolyase family (CPF) comprises flavoproteins that are able to bind damaged or undamaged DNA. Photolyases (PHRs) are enzymes that repair either CPDs or 6-4 PPs. A natural bifunctional CPD/(6-4)- PHR (PhrSph98) was recently isolated from the UV-resistant bacteria Sphingomonas UV9. In this work, phylogenetic studies of bifunctional CPD/(6-4)- photolyases and its evolutionary relationship with other CPF members were performed. Amino acids involved in electron transfer and binding to FAD cofactor and DNA lesions were conserved in proteins from proteobacteria, planctomycete, bacteroidete, acidobacteria and cyanobacteria clades. Genome analysis revealed that the cyanobacteria Synechococcus sp. PCC 7335 encodes a two-gene assembly operon coding for a PHR and a bifunctional CPD/(6-4)- PHR. Operon structure was validated by RT-qPCR analysis and the polycistronic transcript accumulated after 15 minutes of UV-B irradiation. Conservation of structure and evolution is discussed. This is the first report of an UV-B inducible PHRs operon which encodes a CPD/(6-4)- photolyase with putative bifunctional role in the repair of CPDs and 6-4 PPs damages in oxygenic photosynthetic organisms.

evolutionary biology↗

bioRxiv2019

Molecular Cloning and Functional Analysis of the UV-B Photoreceptor Gene ZmUVR8 (UVR8 Response locus), from Zea Mays.

Low UV-B fluence is a signaling stimulus that regulates various physiological processes and induces photomorphogenic responses in plants. The specific UV-B receptor UVR8 is a key component in these processes. Although UVR8 sequence is conserved, few homologs have been cloned and reported to be functional. Here we show the cloning and functional analysis of Zea mays UVR8 (ZmUVR8). ZmUVR8 presents 73% of identity with AtUVR8, maintaining the key tryptophan responsible of UV-B perception. ZmUVR8 also contains the VP domain, involved in the interaction with the proteins CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) and REPRESSOR OF UV-B PHOTOMOPHOGENESIS 1 (RUP1). Whereas UVR8 was expressed in non-irradiated Arabidopsis and maize leaves, after 2h of UV-B irradiation, its expression was reduced. The expression of chalcone synthase (CHS), involved in flavonoid biosynthesis and regulated by UVR8, was increased in irradiated Arabidopsis and maize leaves. Arabidopsis uvr8-1 null mutant was complemented with ZmUVR8 driven by the CaMV-35S promoter and fused to eGFP. ZmUVR8-eGFP fusion was mainly localized in nuclei of transgenic lines, irrespective of UV-B treatments. UV-B suppressed hypocotyl elongation in WT Arabidopsis plants, whereas in uvr8-1 hypocotyl growth was observed. However, hypocotyl elongation was reduced in UV-B irradiated transgenic lines complemented with ZmUVR8. Moreover, CHS and transcription factor HY5 (ELONGATED HYPOCOTYL 5) expression were also restored in these plants. These results confirm that ZmUVR8 is similar enough to AtUVR8 to restore UV-B perception and signaling in Arabidopsis mutant uvr8-1, thus being a functional UV-B photoreceptor.

plant biology↗