Novel roles for phospholipase C in plant stress signalling and development

For many years, efforts have been made to explore PLC signaling in plants. Compared to the classical PLC signaling pathway, a different picture is emerging for plants. Several roles for PLC in plant development and stress responses have been claimed but genetic evidence for this is mostly missing. In this thesis, we functionally characterized the role of PLC3, PLC5 and PLC7 in Arabidopsis.
PLC3 (Chapter 2) was mainly expressed in vasculature. Loss-of-function mutants showed delayed seed germination, shorter primary root, fewer lateral roots, and decreased sensitivity to ABA. PIP2 increase was triggered by ABA, however, no difference in PLC substrate- or product levels in plc3 were found. Overexpression of PLC3 increased the tolerance to drought and decreased stomatal aperture. PLC5 (Chapter 3) was also predominantly expressed in vasculature. plc5 mutant displayed similar root phenotype as plc3. Overexpression of PLC5 enhanced drought tolerance and reduced stomatal aperture but stunted root-hair growth. No differences in PPI and PA between wt and plc5 seedlings, however, decreased PIP and PIP2 and increased PA levels were found in PLC5-OE lines. Inducible overexpression of PIP5K3 in PLC5-OE line rescued the root hair phenotype. PLC7 (Chapter 4) was another phloem-expressed PLC. KO or KD of PLC7 had no effect on root development but was less responsive to ABA. plc3/7 double-knockout mutant was lethal, whereas plc5/7 was viable and revealed several new phenotypes. Overexpression of PLC7 also led to an enhanced drought-tolerant phenotype. Together, these results reveal several novel functions for PLC in plant stress and development.