Poster: Reproductive Development

Abs # 464: The role of phospholipase c in pollen development and pollen tube growth

Presenter:	Dowd, Peter E, peb7@psu.edu
Authors	Dowd, Peter E (A)   Coursol, Sylvie  (B)   Skirpan, Andrea L (A)   Kao, Teh-hui  (A)   Gilroy, Simon  (C)
Affiliations:	(A): The Pennsylvania State University, Biochemistry and Molecular Biology (B): Station de Génétique Végétale (C): The Pennsylvania State University, Biology

Phosphatidylinositols, PI, are a class of membrane phospholipids that are substrates for phosphoinositide-specific phospholipase C (PI-PLC). The biological activity of PIs has been mostly studied in animal cells where they are involved in an array of processes. For example, PIs regulate the activity of phospholipases (such as phospholipase D, PI-PLC itself and protein kinases). In addition, PIs participate in the regulation of vesicle trafficking and in the activity of actin binding proteins. Despite the role of PLC in signal transduction in animals, there is little understanding of the role and regulation of the plant PLCs. PLC cleaves membrane phospholipids to produce diacyl glycerol and a head group product, such as inositol-1,4,5-trisphosphate (IP₃). In pollen, it has been proposed that IP₃ participates in regulating the Ca²⁺ dynamics to control pollen tube elongation. However, the pollen PLC implied by such IP₃ production has not been molecularly identified. We have isolated a full-length PLC cDNA, PetPLC1 (Petunia inflata phosphatidylinositol-specific phospholipase C1) from a pollen/pollen tube cDNA library of P. inflata. When compared to the animal PLC gene family PetPLC1 is most similar to the mammalian d isoform. Like other plant PLCs, it also contains a C2 Ca²⁺/phospholipid binding domain the conserved X and Y catalytic domains, and a region homologous to the 2^nd loop of the Ca²⁺-binding EF hand of PLCd, the "EF loop". PetPLC1 lacks the PH domain involved in membrane targeting and processive catalysis in most animal PLCs. PetPLC1 shows similarity with a number of PLCs in plants (e.g., tobacco, soybean, Arabidopsis). Among Arabidopsis homologs, AtPLC2 is most similar to PetPLC1, sharing 69% amino acid sequence identity