Temperature effects on UV-B induced DNA damage and repair in plants and a lichen

Abstract

All living organisms have DNA and since DNA is essential to life it must be repaired when damaged. UV radiation is one of the major DNA damaging agents, which photosynthetic organisms cannot avoid. The major UV-induced DNA lesions are cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts (6-4PPs) and the main repair pathways of theses lesions involve photolyases and various excision repair systems. Photolyases require longer wavelength UV-A or blue light to induce repair.



This thesis summarises a series of investigations on the effect of temperature (0-30°C) on induction of UV-B induced DNA damage, the photorepair of those UV-lesions and on the activity of purified photolyase in tobacco (<i>Nicotiana tabacum</i>) BY-2 cells and leaves, lingonberry (<i>Vaccinium vitis-idaea</i>) leaves, and <i>Cladonia arbuscula</i> ssp. <i>mitis</i> thalli.



Several studies described here show that the induction of CPDs and 6-4PPs is temperature dependent, with more lesions at higher temperatures. There is variation between species with the most remarkable being that almost no induction of CPDs was detectable in lingonberry at 0°C after 60 minutes of UV-B radiation. Greenhouse grown tobacco showed larger induction of CPDs than naturally growing lingonberry under the same temperature and light conditions. The temperature dependence of the subsequent photorepair <i>in vivo</i> was measured using two different approaches. In the first approach samples were irradiated with UV-B at a given temperature resulting in a constant amount of lesions at the start of the subsequent photorepair experiment under varying temperatures. In the second approach the temperature utilised for induction of damage was the same as that of the following repair, resulting in varying amount of lesions at the start of photorepair. More lesions were generally repaired at higher temperatures than at lower. However, the repair was more efficient at lower temperatures in lingonberry, compared to tobacco leaves. Measurements of CPD-photolyase activity <i>in vitro</i> from tobacco and lingonberry showed little response to temperature increases, indicating that the photochemical reaction is rate-limiting under the conditions used here. The temperature effects on induction and repair <i>in vivo</i> are suggested to be mainly due to effects on the interaction between DNA and other cellular components such as the nucleosomes and the transcriptional apparatus.

Abstract (Swedish)

Popular Abstract in Swedish

Alla levande organismer har DNA, och eftersom DNA är livsnödvändigt måste det repareras om det blir skadat. Ultraviolett (UV) strålning från solen är en av de vanligaste orsakerna till att DNA skadas. De flesta skador på DNA som orsakas av UV-strålning utgörs av cyklobutan-pyrimidindimerer (CPD) eller (6-4)-fotoprodukter. Dessa skador består av två intilliggande baser som binder till varandra, istället för att binda till baserna på den motsatta strängen av DNAt. Båda skadorna är allvarliga eftersom de stoppar produktionen av nya proteiner och blockerar celldelningen.



Växter och andra fotosyntetiserande organismer kan inte helt undvika UV-strålningen eftersom de vill komma åt energin i det synliga ljuset. Däremot har de, i likhet med de flesta andra organismer, ett flertal sätt att reparera uppkomna skador. De vanligaste reparationsmetoderna är med de specifika fotolyaserna eller med mer generella utskärningsenzymer. Utskärningsenzymerna skär bort den skadade delen inklusive en del av DNAts ”ryggrad”, detta hål fylls senare med nytt material. Fotolyaserna är enzymer som endast kan reparera ”sin” typ av skada, CPD-fotolyaserna kan bara reparera CPD:er och (6-4)-fotolyaserna kan bara reparera (6-4)-fotoprodukter. Fotolyaserna binder till skadan och bryter den felaktiga bindningen mellan baserna med hjälp av ljus, de reparerar alltså skadan utan att ta bort de skadade baserna och därför är denna metod alltid felfri.



Länge har man trott att bildandet av DNA-skador orsakade av UV-strålning har varit lika stor oberoende av vid vilken temperatur de uppkommit på. Det har nu visats i ett flertal studier, varav flera finns i denna avhandling, att bestrålning med UV-strålning vid högre temperaturer ger fler DNA-skador än vid lägre, åtminstone mellan 0 och 30°C. Däremot har man länge vetat att reparationen av skadorna har varit temperaturberoende, med mer reparation vid högre temperaturer. Detta motverkar de uppkomna skadorna och tar näst intill ut temperatureffekterna i både skadebildningen och reparationen. I denna avhandling visas dock att detta bara gäller för hela blad och inte för extraherat fotolyas. Dessutom visas det att fotolyaserna inte är så temperaturkänsliga som man tidigare trott, därmed är de tidigare farhågorna angående fotolyasernas känslighet för växthuseffekten överdriven.

• author: Paulsson, Markus
• supervisor: [unknown] [unknown]
• opponent: Professor Breeman, Anneke, Department of Marine Biology, University of Groningen, The Netherlands
• organization: Department of Biology
• publishing date: 2003
• type: Thesis
• publication status: published
• subject: Biological Sciences
• keywords: Tobacco (Nicotiana tabacum), Temperature, Subarctic, Plants, Photoreactivation, Photolyase, Lichen, DNA damage, Cyclobutane pyrimidine dimers (CPD), 6-4 Photoproducts, Cladonia arbuscula ssp. mitis, Ultraviolet radiation, UV-B, Vaccinium vitis-idaea, Plant genetics, Växtgenetik
• pages: 83 pages
• defense location: 5 June 2003, Lecture hall, Biology building, Sölvegatan 35, Lund
• defense date: 2003-06-05 10:15:00
• ISBN: 91-85067-03-2
• language: English
• LU publication?: yes
• additional info: Article: Li S, Paulsson M & Björn L O (2002) Temperature-dependent formation and photorepair of DNA damage induced by UV-B radiation in suspension-cultured tobacco cells. Journal of Photochemistry and Photobiology B: Biology. 66: 67–72. Article: Buffoni Hall R S, Paulsson M, Duncan K, Tobin A K, Widell S & Bornman J F (2003) Water- and temperature-dependence of DNA damage and repair in the fruticose lichen Cladonia arbuscula ssp. mitis exposed to UV-B radiation. Physiologia Plantarum (in press). Article: Paulsson M, Björn L O & Widell S (2003) Temperature effects on UV induced DNA damage and photoreactivation in lingonberry and tobacco leaves. Photochemical and Photobiological Sciences (submitted). The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Department of Cell and Organism Biology (Closed 2011.) (011002100)
• id: 3d17d193-721c-48a3-a297-b25b71b57968 (old id 465937)
• date added to LUP: 2016-04-04 10:03:30
• date last changed: 2018-11-21 20:56:28