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First published online October 13, 2006; 10.1104/pp.106.087882 Plant Physiology 142:1460-1468 (2006) © 2006 American Society of Plant Biologists NAD(P)H Oscillates in Pollen Tubes and Is Correlated with Tip Growth1Department of Biology and Plant Biology Graduate Program, University of Massachusetts, Amherst, Massachusetts 01003 (J.G.K., P.K.H.); Departamento de Biologia Molecular de Plantas, Instituto de Biotecnologia, Universidad Nacional Autónoma de México, Morelos 62271, Mexico (L.C.); and Department of Biology, Long Island University, Brooklyn, New York 11201 (S.T.M.)
The location and changes in NAD(P)H have been monitored during oscillatory growth in pollen tubes of lily (Lilium formosanum) using the endogenous fluorescence of the reduced coenzyme (excitation, 360 nm; emission, >400 nm). The strongest signal resides 20 to 40 µm behind the apex where mitochondria (stained with Mitotracker Green) accumulate. Measurements at 3-s intervals reveal that NAD(P)H-dependent fluorescence oscillates during oscillatory growth. Cross-correlation analysis indicates that the peaks follow growth maxima by 7 to 11 s or 77° to 116°, whereas the troughs anticipate growth maxima by 5 to 10 s or 54° to 107°. We have focused on the troughs because they anticipate growth and are as strongly correlated with growth as the peaks. Analysis of the signal in 10-µm increments along the length of the tube indicates that the troughs are most advanced in the extreme apex. However, this signal moves basipetally as a wave, being in phase with growth rate oscillations at 50 to 60 µm from the apex. We suggest that the changes in fluorescence are due to an oscillation between the reduced (peaks) and oxidized (troughs) states of the coenzyme and that an increase in the oxidized state [NAD(P)+] may be coupled to the synthesis of ATP. We also show that diphenyleneiodonium, an inhibitor of NAD(P)H dehydrogenases, causes an increase in fluorescence and a decrease in tube growth. Finally, staining with 5-(and-6)-chloromethyl-2',7'-dichlorohydrofluorescein acetate indicates that reactive oxygen species are most abundant in the region where mitochondria accumulate and where NAD(P)H fluorescence is maximal.
1 This work was supported by the National Science Foundation (grant nos. MCB–0055799 and MCB–0516852 to P.K.H.) and by Dirección General de Asuntos para el Personal Académico/Universidad Nacional Autónoma de México (grant no. IN–228903 and postdoctoral research to L.C.). The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Luis Cárdenas (luisc{at}ibt.unam.mx). www.plantphysiol.org/cgi/doi/10.1104/pp.106.087882 * Corresponding author; e-mail luisc{at}ibt.unam.mx; fax 52–7773136600. Received August 16, 2006; accepted October 10, 2006; published October 13, 2006. Related articles in Plant Physiol.:
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