Plant Physiology 133: 1445-1452 (2003)

Distinct ultraviolet-signaling pathways in bean leaves. DNA damage is associated with ß-1,3-glucanase gene induction, but not with flavonoid formation

Kucera B, Leubner-Metzger G, Wellmann E

Institut für Biologie II, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany Received July 3, 2003; returned for revision August 17, 2003; accepted September 16, 2003.

Abstract. The enzyme ß-1,3-glucanase (ßGlu) was found to be strongly induced by ultraviolet (UV-B; 280-320 nm) radiation in primary leaves of French bean (Phaseolus vulgaris). This was demonstrated on the level of gene transcription, protein synthesis, and enzyme activity and was due to the expression of bean class I ßGlu (ßGlu I). In contrast to other proteins of the family of pathogenesis-related proteins, the induction of ßGlu I by UV correlated with the formation of photoreversible DNA damage, i.e. pyrimidine dimer formation. In conditions that allowed photorepair of this damage, ßGlu I induction was blocked. Therefore, UV-induced DNA damage seems to constitute a primary signal in the pathway leading to the induction of the ßGlu I gene(s). The induction was a local response because in partly irradiated leaves ßGlu I was selectively found in leaf parts exposed to UV. Although short wavelength UV ( < 295 nm) was most efficient in ßGlu I induction, longer wavelength UV ( > 295 nm) as present in natural radiation was still effective. In contrast to UV induction of ßGlu I, the induction of flavonoids in bean leaves was optimally triggered by much more moderate fluences from the UV wavelength range no longer effective in ßGlu I induction. UV induction of the flavonoid pathway shows no correlation with DNA damage and thus should be mediated via a different signal transduction pathway. Key words: Flavonoids, Gene expression, ß-1,3-Glucanase, Phaseolus, Ultraviolet radiation Hyperlink to a UVB receptor: Rizzini et al. (2011)

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