Plant Cell, Tissue and Organ Culture (PCTOC)

, Volume 104, Issue 2, pp 199–207

Comparison of expression of three different sub-cellular targeted GFPs in transgenic Valencia sweet orange by confocal laser scanning microscopy

Original Paper

DOI: 10.1007/s11240-010-9819-0

Cite this article as:
Xu, SX., Cai, XD., Tan, B. et al. Plant Cell Tiss Organ Cult (2011) 104: 199. doi:10.1007/s11240-010-9819-0


The green fluorescent protein (GFP) has become an ideal visual marker to monitor and quantify the expression of the transgene. It can be targeted to specific subcellular locations, including the endoplasmic reticulum, mitochondria, actin cytoskeleton and nuclei through the addition of signal peptides. Our previous work has resulted in transgenic citrus plants expressing cytoplasmic targeted GFP (Cy-GFP) or endoplasmic reticulum targeted GFP (Er-GFP) gene. To evaluate the localization of three different subcellular targeted GFP, i.e., Cy-GFP, Er-GFP and mitochondria targeted GFP (Mt-GFP) in citrus tissues and to utilize cell lines containing Mt-GFP for basic research in cell fusion, the plasmid pBI-mgfp4-coxIV encoding the Mt-GFP gene was successfully transferred into embryogenic callus of Valencia sweet orange (Citrus sinensis (L.) Osbeck) via Agrobacterium tumefaciens-mediated transformation. Furthermore, we compared the specific expression of these three different subcellular localized GFP constructs in cells of different mature leaf tissues (upper epidermis, palisade parenchyma, spongy parenchyma and lower epidermis) by a confocal laser scanning microscope (CLSM). Cytoplasmic-localized GFP expression was observed throughout the cytoplasm but appeared to accumulate within the nucleoplasm. The Er-GFP occurred within a layer very close to the cell wall. In addition, a stable fluorescence on the ER network throughout the guard cells was detected. Interestingly, the Mt-GFP specifically expressed in the guard cells to particles of about 1–2 μm within the cytoplasm in this case. To verify that the fluorescent particles observable in the guard cells are indeed mitochondria, we co-localize the Mt-GFP fusion protein with a mitochondrial-specific dye in citrus protoplasts. These results demonstrate that the subcellular distribution of the three subcellular targeted GFP is very distinct in citrus leaf cells and the cell lines containing Mt-GFP gene can be further used in citrus basic cell fusion research.


Agrobacterium tumefaciensCitrusCo-localizationConfocal laser scanning microscopeGreen fluorescent protein





Confocal laser scanning microscope


Cytoplasmic targeted GFP


An endoplasmic reticulum targeted GFP


Green fluorescent protein

MT medium

Murashige and Tucker (1969)


Mitochondrial targeted GFP


Neomycin phosphotransferase II

Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • Shi-Xiao Xu
    • 1
  • Xiao-Dong Cai
    • 1
  • Bin Tan
    • 1
  • Wen-Wu Guo
    • 1
  1. 1.Key Laboratory of Horticultural Plant Biology (Ministry of Education)National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural UniversityWuhanChina