Poster: Lipids & Related Molecules

Abs # 853: cDNA cloning and gene expression of phospholipase A₂

Presenter:	Fujikawa, Ritsuko , rfuji@hiroshima-u.ac.jp
Authors	Fujikawa, Ritsuko  (A)   Fujikawa, Yukichi  (A)   Saneoka, Hirofumi  (A)   Iijima, Noriaki  (A)   Esaka, Muneharu  (A)
Affiliations:	(A): Graduate School of Biosphere Science, Hiroshima University

Phosholipase A₂(PLA₂) hydrolyzes glycerophospholipids to produce free fatty acids and lysophospholipids. A number of different PLA₂s have been characterized in animal tissues. Secretory PLA₂(sPLA₂) family has low molecular weight, requires Ca²⁺, and is implicated in a number of biological processes, such as modification of eicosanoid generation, inflammation, and host defense. In plants, little is known about the biological functions of sPLA₂, although there are some reports of purification and cDNA cloning of sPLA₂. We investigated the change in PLA₂ activity during seed germination in pearl millet(Pennisetum glaucum). PLA₂ activity was shown to increase during seed germination. Next, we attempted to isolate cDNA for sPLA₂ from pearl millet. Two partial cDNAs encoding pearl millet sPLA2 were isolated by RT-PCR using transcripts from cotyledon and root of pearl millet as templates. The deduced amino acid sequences have high identities to those from other plant PLA₂s. In order to investigate biological function of sPLA₂ in plants, we cloned two full-length sPLA₂ cDNAs from tobacco(Nicotiana tabacum). Two tobacco PLA₂ proteins encoded by the cDNA have putative signal peptides for translocation into endoplasmic reticulum(ER). Interestingly, one of two PLA₂s contains a possible ER retention signal(KLEL). The PLA₂ may be localized in ER and have some function in ER, without the secretion into extracellular space. RT-PCR analysis showed that two mRNAs were expressed in flower and several developmentally different leaves. Both of sPLA₂ mRNAs were highly expressed in younger leaves. At present, we attempt to investigate response of sPLA₂s expression against environmental stresses in tobacco.