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Overexpression of PwTUA1, a pollen-specific tubulin gene, increases pollen tube elongation by altering the distribution of alpha-tubulin and promoting vesicle transport.

Yu Y, Li Y, Li L, Lin J, Zheng C, Zhang L - J. Exp. Bot. (2009)

Bottom Line: Here, a TUA1 gene from Picea wilsonii, which is specifically expressed in pollen, was isolated.Transient expression analysis in P. wilsonii pollen indicated that PwTUA1 improved pollen germination and pollen tube growth.The possible role of PwTUA1 in microtubule dynamics and organization was discussed.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong 271018, PR China.

ABSTRACT
Tubulin genes are intimately associated with cell division and cell elongation, which are central to plant secondary cell wall development. However, their roles in pollen tube polar growth remain elusive. Here, a TUA1 gene from Picea wilsonii, which is specifically expressed in pollen, was isolated. Semi-quantitative RT-PCR analysis showed that the amount of PwTUA1 transcript varied at each stage of growth of the pollen tube and was induced by calcium ions and boron. Transient expression analysis in P. wilsonii pollen indicated that PwTUA1 improved pollen germination and pollen tube growth. The pollen of transgenic Arabidopsis overexpressing PwTUA1 also showed a higher percentage of germination and faster growth than wild-type plants not only in optimal germination medium, but also in medium supplemented with elevated levels of exogenous calcium ions or boron. Immunofluorescence and electron microscopy showed alpha-tubulin to be enriched and more vesicles accumulated in the apex region in germinating transgenic Arabidopsis pollen compared with wild-type plants. These results demonstrate that PwTUA1 up-regulated by calcium ions and boron contributes to pollen tube elongation by altering the distribution of alpha-tubulin and regulating the deposition of pollen cell wall components during the process of tube growth. The possible role of PwTUA1 in microtubule dynamics and organization was discussed.

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Effects of PwTUA1 overexpression on plant pollen germination and pollen tube growth exposed to different concentrations of boron and Ca2+. (A) Comparison of tube growth of wild-type (WT) and transgenic plant pollen cultured in medium with 0.1% H3BO3 for 6 h. Only the pollen tubes of germinated pollen grains were measured. (B) Arabidopsis pollen was incubated in the germination medium with the indicated amounts of Ca2+. After 6 h of incubation, the percentage of germinating pollen grains was determined. To establish the pollen germination percentage, the percentage germination of pollen grains in at least 10 aliquots per treatment was determined and experiments were repeated three times. (C) Statistical analysis of pollen tube length after 6 h of incubation. Only the pollen tubes of germinated pollen grains were measured. Average lengths of >100 tubes from each line are shown. The experiments were repeated three times, and consistent results were obtained in all repeat experiments.
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fig6: Effects of PwTUA1 overexpression on plant pollen germination and pollen tube growth exposed to different concentrations of boron and Ca2+. (A) Comparison of tube growth of wild-type (WT) and transgenic plant pollen cultured in medium with 0.1% H3BO3 for 6 h. Only the pollen tubes of germinated pollen grains were measured. (B) Arabidopsis pollen was incubated in the germination medium with the indicated amounts of Ca2+. After 6 h of incubation, the percentage of germinating pollen grains was determined. To establish the pollen germination percentage, the percentage germination of pollen grains in at least 10 aliquots per treatment was determined and experiments were repeated three times. (C) Statistical analysis of pollen tube length after 6 h of incubation. Only the pollen tubes of germinated pollen grains were measured. Average lengths of >100 tubes from each line are shown. The experiments were repeated three times, and consistent results were obtained in all repeat experiments.

Mentions: To investigate the function of PwTUA1 during pollen development, this gene was ectopically expressed in Arabidopsis pollen exclusively by using the pollen-specific promoter Lat52. The development of transgenic Arabidopsis pollen was consistent with the results observed for the transformed P. wilsonii pollen grains. Both pollen germination and pollen tube growth were enhanced in the transgenic lines when compared with wild-type Arabidopsis, even at the non-optimal boron or Ca2+ concentrations present in the culture medium (Figs 5, 6A). Pollen expressing the PwTUA1 gene exhibited earlier germination than wild-type pollen exposed to 0.1% H3BO3 (w/v), but resulted in the same germination rate as observed for wild-type pollen. However, pollen germination of the transgenic and wild-type plants was severely and completely inhibited in 1% H3BO3 (data not shown). Furthermore, the pollen tube growth rate of the wild-type plants showed a significant decrease compared with that of transgenic plants. The mean growth rate of wild-type plant pollen tubes was 16.7 μm h−1 compared with 35.6 μm h−1 for pollen tubes of transgenic plants cultured in medium containing 0.1% H3BO3 (Fig. 6A). In the above medium, the concentration of Ca2+ was 0.2 mM.


Overexpression of PwTUA1, a pollen-specific tubulin gene, increases pollen tube elongation by altering the distribution of alpha-tubulin and promoting vesicle transport.

Yu Y, Li Y, Li L, Lin J, Zheng C, Zhang L - J. Exp. Bot. (2009)

Effects of PwTUA1 overexpression on plant pollen germination and pollen tube growth exposed to different concentrations of boron and Ca2+. (A) Comparison of tube growth of wild-type (WT) and transgenic plant pollen cultured in medium with 0.1% H3BO3 for 6 h. Only the pollen tubes of germinated pollen grains were measured. (B) Arabidopsis pollen was incubated in the germination medium with the indicated amounts of Ca2+. After 6 h of incubation, the percentage of germinating pollen grains was determined. To establish the pollen germination percentage, the percentage germination of pollen grains in at least 10 aliquots per treatment was determined and experiments were repeated three times. (C) Statistical analysis of pollen tube length after 6 h of incubation. Only the pollen tubes of germinated pollen grains were measured. Average lengths of >100 tubes from each line are shown. The experiments were repeated three times, and consistent results were obtained in all repeat experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2692020&req=5

fig6: Effects of PwTUA1 overexpression on plant pollen germination and pollen tube growth exposed to different concentrations of boron and Ca2+. (A) Comparison of tube growth of wild-type (WT) and transgenic plant pollen cultured in medium with 0.1% H3BO3 for 6 h. Only the pollen tubes of germinated pollen grains were measured. (B) Arabidopsis pollen was incubated in the germination medium with the indicated amounts of Ca2+. After 6 h of incubation, the percentage of germinating pollen grains was determined. To establish the pollen germination percentage, the percentage germination of pollen grains in at least 10 aliquots per treatment was determined and experiments were repeated three times. (C) Statistical analysis of pollen tube length after 6 h of incubation. Only the pollen tubes of germinated pollen grains were measured. Average lengths of >100 tubes from each line are shown. The experiments were repeated three times, and consistent results were obtained in all repeat experiments.
Mentions: To investigate the function of PwTUA1 during pollen development, this gene was ectopically expressed in Arabidopsis pollen exclusively by using the pollen-specific promoter Lat52. The development of transgenic Arabidopsis pollen was consistent with the results observed for the transformed P. wilsonii pollen grains. Both pollen germination and pollen tube growth were enhanced in the transgenic lines when compared with wild-type Arabidopsis, even at the non-optimal boron or Ca2+ concentrations present in the culture medium (Figs 5, 6A). Pollen expressing the PwTUA1 gene exhibited earlier germination than wild-type pollen exposed to 0.1% H3BO3 (w/v), but resulted in the same germination rate as observed for wild-type pollen. However, pollen germination of the transgenic and wild-type plants was severely and completely inhibited in 1% H3BO3 (data not shown). Furthermore, the pollen tube growth rate of the wild-type plants showed a significant decrease compared with that of transgenic plants. The mean growth rate of wild-type plant pollen tubes was 16.7 μm h−1 compared with 35.6 μm h−1 for pollen tubes of transgenic plants cultured in medium containing 0.1% H3BO3 (Fig. 6A). In the above medium, the concentration of Ca2+ was 0.2 mM.

Bottom Line: Here, a TUA1 gene from Picea wilsonii, which is specifically expressed in pollen, was isolated.Transient expression analysis in P. wilsonii pollen indicated that PwTUA1 improved pollen germination and pollen tube growth.The possible role of PwTUA1 in microtubule dynamics and organization was discussed.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong 271018, PR China.

ABSTRACT
Tubulin genes are intimately associated with cell division and cell elongation, which are central to plant secondary cell wall development. However, their roles in pollen tube polar growth remain elusive. Here, a TUA1 gene from Picea wilsonii, which is specifically expressed in pollen, was isolated. Semi-quantitative RT-PCR analysis showed that the amount of PwTUA1 transcript varied at each stage of growth of the pollen tube and was induced by calcium ions and boron. Transient expression analysis in P. wilsonii pollen indicated that PwTUA1 improved pollen germination and pollen tube growth. The pollen of transgenic Arabidopsis overexpressing PwTUA1 also showed a higher percentage of germination and faster growth than wild-type plants not only in optimal germination medium, but also in medium supplemented with elevated levels of exogenous calcium ions or boron. Immunofluorescence and electron microscopy showed alpha-tubulin to be enriched and more vesicles accumulated in the apex region in germinating transgenic Arabidopsis pollen compared with wild-type plants. These results demonstrate that PwTUA1 up-regulated by calcium ions and boron contributes to pollen tube elongation by altering the distribution of alpha-tubulin and regulating the deposition of pollen cell wall components during the process of tube growth. The possible role of PwTUA1 in microtubule dynamics and organization was discussed.

Show MeSH
Related in: MedlinePlus