Transport of Cl^- across the Plasma Membrane during Pollen Grain Germination in Tobacco

N. P. Matveyeva^*, D. S. Andreyuk, and I. P. Yermakov

Department of Plant Physiology, Faculty of Biology, Lomonosov Moscow State University, Moscow 119899, Russia; fax: (7-095) 939-4309; E-mail: plantphys@biophys.msu.ru

^* To whom correspondence should be addressed.

Received November 28, 2002; Revision received May 12, 2003

---

The role of Cl^- transport across the plasma membrane was studied in an early step of pollen grain germination in tobacco Nicotiana tabacum L. The Cl^- channel blockers, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and niflumic acid, completely suppress the germination with IC₅₀ ~ 8 µM. At this concentration NPPB reduces the rate of Cl^- efflux out of pollen grain by 1.8-fold in the interval 5-12 min, and niflumic acid reduces the rate 1.2-fold. 4,4´-Diisothiocyanatostilbene-2,2´-disulfonic acid, a known inhibitor of Cl^- channels and antiporters, completely suppresses germination as well (IC₅₀ = 240 µM), but has no effect on the rate of Cl^- efflux. Inhibitors of chloride co-transporters, such as furosemide, bumetanide, and bis(1,3-dibutylbarbituric acid)pentamethine oxonol, suppress the germination by less than 50%. This set of data suggests that NPPB-sensitive anion channels are involved in the activation of pollen grains in the early stage of germination.

---

KEY WORDS: anion channel, anion co-transporter, NPPB, DIDS, furosemide, bumetanide, DiBAC₄(5), pollen germination

---