Isolation and functional analysis of sulfite oxidase gene AtSO promoter from Arabidopsis thaliana.

Sulfite oxidase(SO),one of the known mo- lybdenum co-factor-containing enzymes,plays important roles in diverse metabolic processes such as sulfur detoxi- fication and purine catabolism in mammals.But much less is known about the expression and regulatory char- acterization of sulfite oxidase gene in higher plants.In this report,expression of Arabidopsis SO is character- ized in detail by semi-quantitative RT-PCR and his- tochemical staining.The results showed that the tran- scripts of AtSO were predominantly detected in Arabidopsis aerial tissues including stems,young leaves, young inflorescences and immature siliques at higher level,but in roots with a lower level.To monitor AtSO expression in plant,the promoter region containing a 1 562-bp genomic sequence from AtSO was isolated and analyzed using methods of bioinformatics.Basing on the distribution of beta-glucuronidase(GUS)activities shown by histochemical staining in transgenic Arabidopsis plants harboring the promoter-uidA fusion construct,it can be concluded that AtSO is expressed mainly in the green tissues/organs in a light-dependent way.In addition, its expression is up-regulated during sulfite treatment. The information from this study may provide useful clue for further functional analysis of plant SO homologs dur- ing light-induced development of leaf tissue and/or ex- cessive sulfite/SO_2 gas stresses in higher plants.