Subcellular distribution and tissue expression of phospholipase Dα, Dβ, and Dγ in Arabidopsis

Three phospholipase Ds (PLDs; EC 3.1.4.4) have been cloned from Arabidopsis, and they exhibit two distinct types of activities: polyphosphoinositide-requiring PLD beta and PLD gamma, and polyphosphoinositide-independent PLD alpha. In subcellular fractions of Arabidopsis leaves, PLD alpha and PLD gamma were both present in the plasma membrane, intracellular membranes, mitochondria, and clathrin-coated vesicles, but their relative levels differed in these fractions. In addition, PLD gamma was detected in the nuclear fraction. In contrast, PLD beta was not detectable in any of the subcellular fractions. PLD alpha activity was higher in the metabolically more active organs such as flowers, siliques, and roots than in dry seeds and mature leaves, whereas the polyphosphoinositide-dependent PLD activity was greater in older, senescing leaves than in other organs. PLD beta mRNA accumulated at a lower level than the PLD alpha and PLD gamma transcripts in most organs, and the expression pattern of the PLD beta mRNA also differed from that of PLD alpha and PLD gamma in different organs. Collectively, these data demonstrated that PLD alpha, PLD beta, and PLD gamma have different patterns of subcellular distribution and tissue expression in Arabidopsis. The present study also provides evidence for the presence of an additional PLD that is structurally more closely related to PLD gamma than to the other two PLDs.