Thursday, June 16, 2016
Encoding nuclear-associated calcium oscillations required for legume
John Innes Centre, CDB department, Norwich, UK
Nuclear calcium (Ca2+) signals transduce a variety of stimuli in animal and plant cells. Although the autonomy of the nucleus for Ca2+ release has been demonstrated in plants, the nature of the channels responsible for this nuclear Ca2+ release are not known. A wide variety of plant genomes reveal the absence of the canonical nuclear localised Ca2+ channels present in animals, implying alternative mechanisms for nuclear Ca2+ release in plants. Nuclear-associated Ca2+ oscillations play a critical role in plants that respond to beneficial microbial partners: nitrogen-fixing rhizobial bacteria that colonise legume roots and arbuscular mycorrhizal fungi that colonise the vast majority of plant species. Here we show that three cyclic nucleotide gated channels (CNGCs) are required for the generation of symbiotic Ca2+ oscillations in the legume Medicago truncatula. Mutants defective in the three CNGC15 genes are impaired in nuclear Ca2+ oscillations and subsequent symbiotic responses. The CNGCs are localised at the nuclear envelope and are permeable to Ca2+. Furthermore, we demonstrate that the CNGCs form a complex with the nuclear-localised potassium channel DMI1, which modulates nuclear Ca2+ release. The results demonstrate that CNGCs – hitherto known only to be located at vacuoles or the plasma membrane – have been recruited to the nuclear envelope to mediate Ca2+ release, within a larger channel complex. These findings provide the first insights into the channels responsible for nuclear Ca2+ release in plants and imply that as with their counterparts in animal cells, this channel complex might regulate nuclear Ca2+ responses to a variety of developmental and environmental conditions.
Contact : Hervé Sentenac
Contacts IBIP :