DOES A LATERAL GRADIENT OF MEMBRANE POTENTIAL ON THE PLASMA MEMBRANE OF GROWING POLLEN TUBE OF GERMINATING POLLEN GRAIN EXIST?
I. M. Andreev
K. A. Timiryazev Institute of Plant Physiology RAS, Moscow;
e-mail: pmembrane@ippras.ru
The data presented in the article by Breigina et al. (2009) "Changes in the membrane potential during pollen grain germination and pollen tube growth" (Tsitologiya. 51 (10) : 815–823)
and concerning the measurement of electric membrane potential (ΔΨ) on the plasma membrane of growing pollen tube of germinating pollen grain with the use of fluorescent
potential-sensitive dye, di-4-ANEPPS, were critically analyzed in order to clarify whether a lateral gradient of ΔΨ on this membrane indeed exists. This analysis showed that the
main conclusion of the authors of the above article on the existence of polar distribution of ΔΨ along the pollen tube plasma membrane is not in accordance with a number of known
peculiarities of di-4-ANEPPS behavior in biological membranes and requires a significant revision. The findings in question reported by the authors, in my opinion, might be interpreted as
evidence for the presence on the plasma membrane of growing pollen tube not only the membrane potential ΔΨ but also lateral gradient of so called intra-membrane dipole potential.
Based on the comments made, another interpretation of the experimental results described by Breigina et al. has been offered. In addition, some drawbacks in the methodology used by the
authors for measurement of ΔΨ with other fluorescent potential-sensitive dye, DiBAC3(3), are also shortly considered.
Key words: plasma membrane, membrane potential, pollen tube, potential-sensitive dye
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