Stubborn GFPs in Nicotiana tabacum vacuoles

Green fluorescent protein (GFP) allows the direct visualization of gene expression and sub cellular localization of fusion proteins in living cells. Many GFP variants have been developed to solve stability and emission problems. In this report the localization of different GFP fusion proteins, targeted to vacuoles, was studied in Nicotiana tabacum cv SRI. Even if a strong emission variant of the plant adapted GFP was used, no fluorescence was detected in differentiated tissues of N. tabacum with few exceptions. This model plant does not appear a good experimental system for the use of GFPs as vacuolar markers compared to Arabidopsis thaliana. In spite of this, our observations have evidenced a peculiar pattern of separated vacuoles in guard cells, providing new elements in the understanding of the vacuolar system organization.