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.
Leibniz University of Hannover, Institute of Floriculture and Wood Science, Section of Applied Molecular Physiology, Herrenhäuser Strasse 2, D-30419 Hannover, Germany.
Rinukshi
R
Wimalasekera
Premysl
P
Pejchar
André
A
Holk
Jan
J
Martinec
Günther F E
GF
Scherer
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