Molecular Identification of Cytosolic, Patatin-Related Phospholipases A from Arabidopsis with Potential Functions in Plant Signal Transduction

Abstract

Rapid activation of phospholipase A (PLA) by auxin or plant-pathogen interaction suggests a function in signal transduction for this enzyme, but the molecular identification of a cytosolic PLA carrying out this function remains open. We isolated four cDNA sequences from Arabidopsis (ecotype Columbia), AtPLA I, AtPLA IIA, AtPLA IVA, and AtPLA IVC, which are members of the patatin-related PLA gene family in plants and which are homologous to the animal Ca 2ϩ -independent PLA 2 gene family. Expression was measured by reverse transcriptase-polymerase chain reaction, and AtPLA I transcripts were found preferentially in shoots, AtPLA IIA and AtPLA IVA in roots, and AtPLA IVC in flowers. Transient expression of the four PLA-green fluorescent protein fusion proteins in tobacco (Nicotiana tabacum) leaves showed they were located in the cytosol and not in the vacuoles. Surprisingly, AtPLA::green fluorescent protein was also localized to chloroplasts. The enzymatic activity of the purified recombinant AtPLA IVA toward phosphatidylcholine was dependent on Ca 2ϩ , saturated at 0.5 mm, and had a pH optimum of about 7.0. It had both PLA 1 and PLA 2 specificity. The enzyme showed in vitro highest sensitivity toward the PLA 2 inhibitors palmitoyltrifluoromethyl ketone (PACOCF 3 , K i approximately 30 nm), arachidonyltrifluoromethyl ketone (AACOCF 3 , K i approximately 25 m), and tetrahydro-3-(1-naphtalenyl)-2H-pyran-2-one (K i approximately 200 nm) and was also sensitive to other previously used inhibitors 5,8,11,14-eicosatetraynoic acid (K i approximately 3 m) and nordihydroguajaretic acid (K i approximately 15 m). The influence of these PLA 2 inhibitors on elongation in etiolated Arabidopsis seedlings was tested, and tetrahydro-3-(1-naphtalenyl)-2H-pyran-2-one and 5,8,11,14-eicosatetraynoic acid inhibited hypocotyl elongation maximally at concentrations close to their K i in vitro.

SOBER1 phospholipase activity suppresses phosphatidic acid accumulation and plant immunity in response to bacterial effector AvrBsT

“…A number of PLA 2 enzymes have been linked to plant defense signaling (33). The majority of theses proteins are patatinrelated plant PLAs (34)(35)(36)(37). Interestingly, AtPLP2 is a plant susceptibility factor during fungal and bacterial infection (37).…”

“…Interestingly, AtPLP2 is a plant susceptibility factor during fungal and bacterial infection (37). By contrast, other PLA 2 s promote cell death associated with defense and development (34)(35)(36)38). SOBER1, however, is not homologous to any members in the Arabidopsis PLA family (33).…”

Lipid and oxylipin profiles during aging and sprout development in potato tubers (Solanum tuberosum L.)

“…These data suggest that the lipase(s) that produce the free fatty acids used as LOX substrates must have removed the fatty acids from both the sn1 and sn2 positions of polar lipids, without accumulation of lysoPC or lysoPE. In fact, lipases found in potato tuber vacuoles, the patatins, have low specificity; recently it was demonstrated that a recombinant patatin-like Arabidopsis enzyme is capable of hydrolysing acyl groups from both sn1 and sn2 positions of phospholipids [37]. Between 60 and 90 days of aging, PA, lysoPC, and lysoPE levels all increased 2 -3-fold.…”

Transcriptional Profiling of Sorghum Induced by Methyl Jasmonate, Salicylic Acid, and Aminocyclopropane Carboxylic Acid Reveals Cooperative Regulation and Novel Gene Responses

“…4). Patatin also exhibits phospholipase A2 functionality (Dhondt et al, 2000;Holk et al, 2002), and expression of a number of sorghum patatin homologs was induced sharply by MeJA and also moderately by SA (Fig. 4).…”