Unequal distribution of ubiquitinated proteins during Pinus bungeana pollen development |
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Authors: | Xianyong Sheng Xiaoling Dong Shasha Zhang Liping Jiang Lingling Tan Xue Li |
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Institution: | (1) College of Life Science, Capital Normal University, North Xisanhuan 105, 100048 Beijing, China;(2) College of Life Science, Qingdao Agricultural University, 266109 Qingdao, China |
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Abstract: | The production of gametogenesis is a charming and complicated event in higher plants, during that stage the protein population
undergoes substantial alterations. But few attentions have been paid to the possible roles of the UPP in gymnosperm gametogenesis.
In the present study, DNA-specific probe 4′,6-dimidino-phenylindole was employed to assess Pinus bungeana pollen developmental stage. It was revealed that the division of pollen mother cell occurred in late April. The uninucleate
microspore then underwent three asymmetric divisions, forming a mature pollen grain including a tube cell and a generative
cell together with two degenerated prothallial cells in early May. Immunofluorescence labeling of ubiquitinated proteins (UbPs)
with an anti-ubiquitin antibody indicated that fluorescence signal was detected in both cytosol and nuclear of the microspore
at the uninucleate stage. In the two-cell pollen grain, a brighter fluorescence was always detected in the first prothallial
when compared with that in central cell. Similarly, unequal distribution of UbPs was observed again during the division of
the central cell into the antheridial initial and the second prothallial cell. The high intensity of the fluorescence in the
two degenerated prothallial cells remained in the mature pollen grain, but only a faint signal could be detected in the tube
cell or the generative cell deriving from the division of the antheridial initial. The unequal distribution of UbPs was further
unveiled by immunogold labeling among prothallial cells, generative cells and tube cells in mature pollen grains. Besides,
Coomassie brilliant blue cytochemistry was also performed to illustrate the general subcellular distribution of total proteins
in the two-cell and matured pollen grains. All these results indicated that the prothallial cells have high ratio of UbPs,
and that the ubiquitin-mediated proteolysis might have an important role during pine pollen development. |
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