Abstract
Cytosolic free calcium ([Ca2+]cyt), which is essential during pollen germination and pollen tube growth, can be sensed by calmodulin-like proteins (CMLs). The Arabidopsis thaliana genome encodes over 50 CMLs, the physiological role(s) of most of which are unknown. Here we show that the gene AtCML24 acts as a regulator of pollen germination and pollen tube extension, since the pollen produced by loss-of-function mutants germinated less rapidly than that of wild-type (WT) plants, the rate of pollen tube extension was slower, and the final length of the pollen tube was shorter. The [Ca2+]cyt within germinated pollen and extending pollen tubes produced by the cml24 mutant were higher than their equivalents in WT plants, and pollen tube extension was less sensitive to changes in external [K+] and [Ca2+]. The pollen and pollen tubes produced by cml24 mutants were characterized by a disorganized actin cytoskeleton and lowered sensitivity to the action of latrunculin B. The observations support an interaction between CML24 and [Ca2+]cyt and an involvement of CML24 in actin organization, thereby affecting pollen germination and pollen tube elongation.
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Acknowledgments
We thank Janet Braam (Biochemistry and Cell Biology, Rice University, Texas, USA) for providing the cml24-4 mutants used in our experiments, and ABRC for supplying the cml24-T1 T-DNA insertion line. We are grateful to Timothy E. Gookin for critical reading of the manuscript. This work was supported by the Natural Science Foundation of China (31170236 and 31271506 to W.Z.) and open fund of State Key Laboratory of Plant Physiology and Biochemistry (SKLPPBKF11003 to W.Z.).
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Yang, X., Wang, SS., Wang, M. et al. Arabidopsis thaliana calmodulin-like protein CML24 regulates pollen tube growth by modulating the actin cytoskeleton and controlling the cytosolic Ca2+ concentration. Plant Mol Biol 86, 225–236 (2014). https://doi.org/10.1007/s11103-014-0220-y
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DOI: https://doi.org/10.1007/s11103-014-0220-y