Plant phosphatidylcholine-hydrolyzing phospholipases C NPC3 and NPC4 with roles in root development and brassinolide signaling in Arabidopsis thaliana.
Phosphatidylcholine-hydrolyzing phospholipase C (PC-PLC) catalyzes the hydrolysis of phosphatidylcholine (PC) to generate phosphocholine and diacylglycerol (DAG). PC-PLC has a long tradition in animal signal transduction to generate DAG as a second messenger besides the classical phosphatidylinositol splitting phospholipase C (PI-PLC). Based on amino acid sequence similarity to bacterial PC-PLC, six putative PC-PLC genes (NPC1 to NPC6) were identified in the Arabidopsis genome. RT-PCR analysis revealed overlapping expression pattern of NPC genes in root, stem, leaf, flower, and silique. In auxin-treated P(NPC3):GUS and P(NPC4):GUS seedlings, strong increase of GUS activity was visible in roots, leaves, and shoots and, to a weaker extent, in brassinolide-treated (BL) seedlings. P(NPC4):GUS seedlings also responded to cytokinin with increased GUS activity in young leaves. Compared to wild-type, T-DNA insertional knockouts npc3 and npc4 showed shorter primary roots and lower lateral root density at low BL concentrations but increased lateral root densities in response to exogenous 0.05-1.0 μM BL. BL-induced expression of TCH4 and LRX2, which are involved in cell expansion, was impaired but not impaired in repression of CPD, a BL biosynthesis gene, in BL-treated npc3 and npc4. These observations suggest NPC3 and NPC4 are important in BL-mediated signaling in root growth. When treated with 0.1 μM BL, DAG accumulation was observed in tobacco BY-2 cell cultures labeled with fluorescent PC as early as 15 min after application. We hypothesize that at least one PC-PLC is a plant signaling enzyme in BL signal transduction and, as shown earlier, in elicitor signal transduction.
Wimalasekera
Rinukshi
R
Leibniz University of Hannover, Institute of Floriculture and Wood Science, Section of Applied Molecular Physiology, Herrenhäuser Strasse 2, D-30419 Hannover, Germany.
Pejchar
Premysl
P
Holk
André
A
Martinec
Jan
J
Scherer
Günther F E
GF
D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D060406:Brassinosteroids; D002460:Cell Line; D002777:Cholestanols / Q000494:pharmacology*; D010802:Phylogeny; D018517:Plant Roots / Q000254:growth & development* / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013260:Steroids, Heterocyclic / Q000494:pharmacology*; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism; D010738:Type C Phospholipases / Q000145:classification / Q000235:genetics / Q000378:metabolism*
D060406:Brassinosteroids; D002777:Cholestanols; D013260:Steroids, Heterocyclic; D010738:Type C Phospholipases; C105598:phosphatidylcholine-specific phospholipase C; C023623:brassinolide