Promoter Analysis for Three Types of EUL-Related Rice Lectins in Transgenic Arabidopsis

In this study, the promoter activity for three types of Euonymus-related lectins (EUL) from rice, further referred to as OrysaEULS2, OrysaEULS3, and OrysaEULD1A was analyzed. In silico promoter analyses showed that the EUL promoters from rice contain next to the typical promoter elements some motifs that are considered to be stress-responsive elements. Furthermore, Arabidopsis thaliana plants were transformed with a promoter::β-glucuronidase (GUS) construct for each of the proteins under study. Subsequently, one-insertion homozygous lines were selected and analyzed for GUS activity. Experiments were performed under normal growth conditions or after application of different stress conditions, in particular treatments with 150 mM NaCl, 100 mM mannitol, and 100 μM abscisic acid (ABA) for 24 h. GUS activity was detected with the OrysaEULS3 and OrysaEULD1A promoters especially in the cotyledons and the young true leaves, respectively, but not with the OrysaEULS2 promoter. The activity of OrysaEULS3 and OrysaEULD1A promoters was increased after ABA and mannitol treatments but decreased after NaCl treatment. We hypothesize that the Euonymus-related rice proteins have a role in sensing and responding to external stresses as well as in the growth of the plant.