The effect of UV-B on freezing tolerance in Arabidopsis thaliana

Abstract

Cold stress causes significant crop losses each year. Some plants can withstand this stress through the upregulation of genes which result in cold acclimation. This process involves the C-REPEAT BINDING FACTOR (CBF) regulon and COLD RESPONSE (COR) gene expression which protect the plant from low temperature damage. The signalling pathway that leads to cold acclimation is therefore of interest when investigating how to protect plants from low temperature stress. When multiple signalling pathways converge in a process known as crosstalk, enhanced resistance to a stress can result. Previous studies have shown that UV-B can enhance the survivability of Rhododendron at low temperatures and increase expression of protective enzymes involved in cold resistance in Triticum aestivum. This phenomenon has not been investigated in the model species, Arabidopsis thaliana. Here, the interaction of UV-B and cold acclimation in Arabidopsis is explored. An enhancement of COR15a and COR47 transcript abundance was observed when cold acclimation occurred in the presence of UV-B, but this was not accompanied by increased plant survival following freezing stress at -6 oC. The role of flavonoids in cold and UV-B signalling was also analysed as flavonoids are known to be involved in both plant freezing tolerance and UV-B protection. Mutants deficient in flavonoid biosynthesis, transparent testa 4 (tt4) and tt7 showed decreased survival following a freezing stress. This response was further exacerbated by UV-B treatment. The combination of cold and UV-B resulted in greater levels of CHALCONE SYNTHASE (CHS) transcript and flavonoid accumulation than either treatment alone, suggesting a synergistic interaction. Together, these data suggest that crosstalk exists between low temperature and UV-B signalling and that UV-B could be used conditionally to enhance cold acclimation and increase freezing tolerance in Arabidopsis.

Date of Award	28 Nov 2019
Original language	English
Awarding Institution	The University of Bristol
Supervisor	Antony Dodd (Supervisor) & Keara A Franklin (Supervisor)