Extracellular ATP is involved in the initiation of pollen germination and tube growth in Picea meyeri
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Gymnosperm pollen grains release ATP to the extracellular matrix which is essential for the initiation of pollen germination and tube growth.
Extracellular ATP (eATP) is an important signaling compound involved in various processes of animal and angiosperm cells. However, the role played by eATP in gymnosperm cells remains unclear. Using a bioluminescence assay, we found that pollen grains of Picea meyeri released ATP to the extracellular matrix before germination and during tube elongation. The addition of further exogenous ATP or an apyrase inhibitor to pollen suspensions inhibited germination and pollen tube elongation. Exogenous apyrase (which hydrolyzes eATP released from pollen per se) exerted a similar inhibitory effect. Moreover, incubation of pollen suspensions with purinoceptor inhibitors prevented germination. ATP intensified the influx of Ca2+ after germination, which was abrogated by purinoceptor inhibitors. Confocal microscopy revealed that the microfilament pattern became disorganized in pollen tubes when exposed to ATP. Together, our findings suggest that optimum concentration of eATP is essential for initiation of pollen germination, and eATP signaling regulates pollen tube growth by activating purinoceptors to increase Ca2+ influx, thus modulating microfilament organization, which, in turn, is essential for pollen germination and tube growth. Hence, we provide a mechanistic framework for the role played by eATP in pollen germination and tube growth.
KeywordsPicea meyeri Pollen germination Pollen tube growth eATP Gymnosperm
Author contribution statement
Yanping Jing and Junhui Zhou designed the experiment, Junhui Zhou performed most of the experimental work, Kai Liu carried out ATP assay experiment, Junhui Zhou and Chengyu Fan wrote the paper. All authors read and approved the final manuscript.
This work was supported by grants from the National Natural Science Foundation of China (No. 31371348), Program for Changjiang Scholars and Innovative Research Team in University (No. IRT13047).
Conflict of interest
We declare that we have no conflict of interest.