Poster: Oxidative Stress

Abs # 127: Expression analysis of a germin-like protein with Mn-superoxide dismutase activity in a moss, Barbula unguiculata

Presenter:	Nakata, Masaru , bozikun@hiroshima-u.ac.jp
Authors	Nakata, Masaru  (A)   Shiono, Tadahiko  (A)   Watanabe, Yayoi  (A)   Hashimoto, Yuka  (A)   Satoh, Toshio  (A)
Affiliations:	(A): Dept. Biol.Sci., Grad. Sch. Sci., Hiroshima Univ.

Germins and germin-like proteins (GLPs) have been found in various plants. Although the expressions of some germins and GLPs were induced by environmental stresses and pathogen infections, their physiological functions have not been clarified yet. We first isolated a germin-like protein with Mn-SOD activity from a moss, Barbula unguiculata, and designated BuGLP. Our purpose in this study is to bring out physiological roles of BuGLP taking note of its SOD activity. When NaCl was added into the cells the BuGLP mRNA levels increased, but most of BuGLP protein was released into the medium. On the other hand, the addition of methyl viologen as a generator of superoxide or H₂O₂ decreased the BuGLP mRNA levels dose dependently. The addition of H₂O₂ in the presence of NaCl decreased the BuGLP mRNA levels compared with those in the presence of NaCl alone, followed by the release of BuGLP protein into the medium, too. These results suggest that H₂O₂ generated from superoxide by BuGLP plays an important role in regulation of BuGLP expression. In order to clarify the mechanisms that cause these regulations, the promoter region of BuGLP gene was cloned. Analysis of databases of plant cis-acting regulatory elements revealed that there are some plant hormone or light responsive elements as well as environmental stresses-responsive elements. The addition of abscisic acid (ABA) decreased BuGLP mRNA levels like the effect of H₂O₂, being in agreement with the results that reactive oxygen species are induced by ABA and essential intermediates in ABA signaling.