Organ-specificity and inducibility of patatin class I promoter from potato in transgenic arabidopsis plants

Abstract

Patatin class I promoter (B33 promoter) is a tissue-specific potato (Solanum tuberosum L.) promoter expressing the patatin gene mainly in tubers. However, it can be induced in other organs by sucrose or light. We compared the activity of this promoter fused with the reporter gene during heterological expression in B33::GUS transgenic arabidopsis (Arabidopsis thaliana L.) plants and homological expression of the same DNA construct in potato. Promoter activity was estimated from quantification of β-glucuronidase (GUS) activity. It was shown that, during heterological expression in arabidopsis seedlings, B33 promoter manifested a tissue-specificity and inducibility, although in a different manner than during homological expression in potato. In noninduced arabidopsis seedlings, B33 promoter was most active in the roots, whereas, after induction with sucrose treatment, it became most active in cotyledons. 10 mM sucrose was sufficient for a manifold activation of B33 promoter in intact seedlings. The degree of B33 promoter induction by sucrose in arabidopsis seedlings was strictly organ-specific and increased in the following sequence: root < hypocotyl < cotyledons. 150–200 mM sucrose enhanced B33 promoter activity in cotyledons by 200 to 300 times, i.e., much stronger than in potato organs. Glucose and fructose were less efficient than sucrose. Phytohormones affecting tuber formation in potato (gibberellins, auxins, and cytokinins) did not affect significantly B33 promoter activity in arabidopsis. A lag period of approximately 6 h preceded sucrose-induced B33 promoter activation. This indicates that the patatin promoter is not the primary target for the sucrose signal. The quantitative examination of heterological expression of patatin class I promoter further clarifies its basic functional characteristics and permits a better prognosis of its behavior after transferring into other plant species.