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CELL BIOLOGY AND SIGNAL TRANSDUCTION

The Pollen Receptor Kinase LePRK2 Mediates Growth-Promoting Signals and Positively Regulates Pollen Germination and Tube Growth^1,[W],[OA]

Shanghai Institutes for Biological Sciences-University of California at Berkeley Center of Molecular Life Sciences, National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (D.Z., C.-P.G., W.-H.T.); Instituto de Ingeniería Genética y Biología Molecular, CONICET Departamento de Fisiología y Biología Molecular y Celular FCEN, Universidad de Buenos Aires, Obligado 2490, 1428 Buenos Aires, Argentina (D.W., J.M.); and Plant Gene Expression Center, United States Department of Agriculture/Agricultural Research Service, and Department of Plant and Microbial Biology, University of California at Berkeley, Albany, California 94710 (D.W., B.S., S.M., W.-H.T.)

In flowering plants, the process of pollen germination and tube growth is required for successful fertilization. A pollen receptor kinase from tomato (Solanum lycopersicum), LePRK2, has been implicated in signaling during pollen germination and tube growth as well as in mediating pollen (tube)-pistil communication. Here we show that reduced expression of LePRK2 affects four aspects of pollen germination and tube growth. First, the percentage of pollen that germinates is reduced, and the time window for competence to germinate is also shorter. Second, the pollen tube growth rate is reduced both in vitro and in the pistil. Third, tip-localized superoxide production by pollen tubes cannot be increased by exogenous calcium ions. Fourth, pollen tubes have defects in responses to style extract component (STIL), an extracellular growth-promoting signal from the pistil. Pollen tubes transiently overexpressing LePRK2-fluorescent protein fusions had slightly wider tips, whereas pollen tubes coexpressing LePRK2 and its cytoplasmic partner protein KPP (a Rop-GEF) had much wider tips. Together these results show that LePRK2 positively regulates pollen germination and tube growth and is involved in transducing responses to extracellular growth-promoting signals.

² These authors contributed equally to the article.

³ Present address: Department of Biological Sciences, Wichita State University, Wichita, KS 67260.

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: Wei-Hua Tang (whtang{at}sibs.ac.cn).

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.124420

^* Corresponding author; e-mail whtang{at}sibs.ac.cn.

Received June 11, 2008; accepted September 10, 2008; published September 17, 2008.

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