Ca2+ dynamics in a pollen grain and papilla cell during pollination of Arabidopsis |
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| Authors: | Iwano Megumi Shiba Hiroshi Miwa Teruhiko Che Fang-Sik Takayama Seiji Nagai Takeharu Miyawaki Atsushi Isogai Akira |
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| Affiliation: | Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0101, Japan. m-iwano@bs.naist.jp |
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| Abstract: | Ca2+ dynamics in the growing pollen tube have been well documented in vitro using germination assays and Ca2+ imaging techniques. However, very few in vivo studies of Ca2+ in the pollen grain and papilla cell during pollination have been performed. We expressed yellow cameleon, a Ca2+ indicator based on green fluorescent protein, in the pollen grains and papilla cells of Arabidopsis (Arabidopsis thaliana) and monitored Ca2+ dynamics during pollination. In the pollen grain, Ca2+]cyt increased at the potential germination site soon after hydration and remained augmented until germination. As in previous in vitro germination studies, Ca2+]cyt oscillations were observed in the tip region of the growing pollen tube, but the oscillation frequency was faster and Ca2+]cyt was higher than had been observed in vitro. In the pollinated papilla cell, remarkable increases in Ca2+]cyt occurred three times in succession, just under the site of pollen-grain attachment. Ca2+]cyt increased first soon after pollen hydration, with a second increase occurring after pollen protrusion. The third and most remarkable Ca2+]cyt increase took place when the pollen tube penetrated into the papilla cell wall. |
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