The V‐PLC3 gene encodes a putative plasma membrane‐localized phosphoinositide‐specific phospholipase C whose expression is induced by abiotic stress in mung bean (Vigna radiata L.)¹

Abstract

Phosphoinositide-speci¢c phospholipase C (PI-PLC) catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate to generate inositol 1,4,5-trisphosphate and diacylglycerol, both of which act as secondary messengers in animal cells. In this report, we identi¢ed in Vigna radiata L. (mung bean) three distinct partial cDNAs (pVr-PLC1, pVr-PLC2, and pVr-PLC3), which encode forms of putative PI-PLC. All three Vr-PLC genes were transcriptionally active and displayed unique patterns of expression. The Vr-PLC1 and Vr-PLC2 transcripts were constitutively expressed to varying degrees in every tissue of mung bean plants examined. In contrast, the Vr-PLC3 mRNA level was very low under normal growth conditions and was rapidly induced in an abscisic acid-independent manner under environmental stress conditions (drought and high salinity). An isolated genomic clone, about 8.2 kb in length, showed that Vr-PLC1 and Vr-PLC3 are in tandem array in the mung bean genome. The predicted primary sequence of Vr-PLC3 (M r = 67.4 kDa) is reminiscent of the N N-isoform of animal enzymes which contain core sequences found in typical PI-PLCs, such as the catalytic domain comprising X and Y motifs, a lipid-binding C2 domain, and the less conserved EFhand domain. Results of in vivo targeting experiment using a green £uorescent protein (GFP) showed that the GFP-Vr-PLC3 fusion protein was localized primarily to the plasma membrane of the Arabidopsis protoplast. The C2 domain was essential for Vr-PLC3 to be targeted to the plasma membrane. The possible biological functions of stress-responsive Vr-PLC3 in mung bean plants are discussed.

Pollen Tube Tip Growth Depends on Plasma Membrane Polarization Mediated by Tobacco PLC3 Activity and Endocytic Membrane Recycling

“…It has been suggested that the C2 domain of plant PI-PLCs alone may mediate the membrane association of these proteins (MuellerRoeber and Pical, 2002). Consistent with this proposal, deletion of the C2 domain abolished the membrane association of mung bean (Vigna radiata) PLC3 (Kim et al, 2004), and the EF hands of Arabidopsis thaliana PLC2 (which correspond to EF hands 3 and 4 of animal PI-PLC-ds) were not required for lipid binding in vitro, although they were essential for catalytic activity (Otterhag et al, 2001).…”

“…Interestingly, plant PI-PLCs, although they appear to be at least partially membrane-associated (Shi et al, 1995;Kim et al, 2004), are missing the PH domain and the first two EF hands required for membrane targeting of animal PI-PLC-ds. It has been suggested that the C2 domain of plant PI-PLCs alone may mediate the membrane association of these proteins (MuellerRoeber and Pical, 2002).…”

“…Whereas little is known about the physiological functions of animal PI-PLC-ds, the expression of different plant PI-PLCs has been shown to be induced under stress conditions (Kopka et al, 1998;Kim et al, 2004;Vergnolle et al, 2005). Abscisic acid induction of seed dormancy (Sanchez and Chua, 2001) and stomatal closure (Staxé n et al, 1999;Hunt et al, 2003) was blocked by reducing PI-PLC activity using genetic knockdown or the specific inhibitor U-73122, which establishes a function of PIPLCs in abscisic acid signaling.…”

Zea mays Annexins Modulate Cytosolic Free Ca2+ and Generate a Ca2+-Permeable Conductance

“…The C2 domain mediates Ca 2+ -dependent phospholipid binding (Nalefski and Falke, 1996). Although few C2-containing proteins have been characterized in plants, the domain has been shown to be essential for plasma membrane association of a mung bean (Vigna radiata) phospholipase C (Kim et al, 2004) and a novel bell pepper protein (Kim et al, 2008). To date, plant C2 domain proteins appear to be involved in (a)biotic stress responses and development (Kim et al, 2004(Kim et al, , 2008Yang et al, 2008), suggesting that the novel maize p23 protein could be involved in such Ca 2+ -dependent processes.…”

Differential gene expression and mitotic cell analysis of the drought tolerant soybean (Glycine max L. Merrill Fabales, Fabaceae) cultivar MG/BR46 (Conquista) under two water deficit induction systems

“…However, under dehydration many authors suggest that the lowering of turgor caused by water loss causes conformational changes in membrane sensory proteins, altering linkage of hormones (produced in other dehydrated cells) and also altering functionality of transfer proteins such as PITP. Changes in cytsolic Ca 2+ level can activate many response genes to drought (Kim et al, 2004;Har et al, 1996). Studies in higher plants have produced evidence that variations in cytosolic Ca 2+ can be related to transduction signal mechanisms during drought and high salinity stress.…”