A mutation in ELA1, an age-dependent negative regulator of PAP1/MYB75, causes UV- and cold stress-tolerance in Arabidopsis thaliana seedlings

UV light is one of several severe abiotic stresses encountered by terrestrial plants. It is impairing cellular metabolism and causing cell death by damaging DNA, proteins, and lipids. Phenolics including various flavonoids serve as "sunscreens" to UV exposure; in particular, flavonoids play pivotal roles in absorbing free radicals, quenching singlet oxygen, and decomposing peroxides. Here, we screened Arabidopsis thaliana for a UV-tolerant mutant with elevated flavonoid levels, and identified the recessive ela1 mutant. We demonstrate that the enhanced UV stress-tolerance shown in the ela1 mutant seems to be conferred by high levels of UV-absorbing pigments such as anthocyanins. The ela1 mutant exhibited novel characteristics as a negative regulator of PAP1 and cold stress-tolerance, and its role is specific to early stages of A. thaliana development. Our results clearly suggest that flavonoid biosynthesis is regulated by a developmental program where ELA1 participates as an important regulatory component.