Ureides are similarly accumulated in response to UV-C irradiation and wound but differently remobilized during recovery in Arabidopsis leaves

Abstract

To examine a role of purine degraded metabolites in response to wounding or UV-C stress, the Arabidopsis wild-type and Atxdh1 KO mutants, defective in xanthine dehydrogenase1 (XDH1), were exposed to wounding and UV-C irradiation stress. In Atxdh1 mutant, wounding or UV-C stresses resulted in lower fresh-weight, increased senescence symptoms and higher tissue cell death rate compared to Wild-type. Additionally, Wild-type exhibited lower levels of oxidative stress indicators; reactive oxygen species and malondialdehyde than Atxdh1 mutant leaves. Notably, purine degradation transcripts and proteins were orchestrated to lead to enhanced ureide levels in Wild-type leaves 24 h after applying UV-C or wound stress. Yet, different remobilization of the accumulated ureides was noticed 72 h after stresses application. In plants treated with UV-C the allantoin level was highest in young leaves, whereas in wounded plants it was lowest in the young leaves, accumulated mainly in the middle and wounded leaves. The results indicate that in UV-C treated Wild-type, during the recovery period from stress, ureides are remobilized from the lower older leaves to support young leaf growth. In contrast, after wounding, the ureides are remobilized to the young leaves, yet more to the middle wounded leaves, to function as antioxidants and/or healing agents.