Spatial Localization of Germin-Like Oxalate Oxidase Genes in Developing Wheat Shoots

ABSTRACT

When quiescent embryos in dry grains of ripened wheat are isolated and provided with ample water and oxygen at an appropriate temperature, they begin to grow very rapidly. The onset of the growth is signaled by nascent synthesis of germin genes which encodes a relatively rare, water-soluble homop entameric glycoprotein. Germin is resistant to pepsin digestion under conditions that lead to hydrolysis of virtually all other proteins in wheat embryos. Germin proteins have oxalate oxidase activity, an activity that degrades oxalic acid to generate hydrogen peroxide which involves in many aspects of plant development.

Following 48-hour imbibition on water, wheat embryos give rise to distinguishable shoot and roots. Shoots comprise coleoptile, leaf primordium and shoot apex. In the current study, non-radioactively labeled germin riboprobes were prepared by in vitro transcription. The riboprobes were used to search and localize germin mRNAs in sections taken from throughout of shoots. The results revealed that although leaf primordium and shoot apex did not show any signals of the presence of germin mRNAs, coleoptiles as a whole tissue displayed germin gene expression on epidermal cells and vascular bundle sheath cells. Among the sections taken from different parts of shoots, the sections from middle part gave the strongest signals on coleoptile cells.