A quantitative hypermorphic CNGC allele confers ectopic calcium flux and impairs cellular development

Abstract

The coordinated control of Ca2+ signaling is essential for development in eukaryotes. Cyclic nucleotide-gated channel (CNGC) family members mediate Ca2+ influx from cellular stores in plants (Charpentier et al., 2016; Gao et al., 2016; Frietsch et al., 2007; Urquhart et al., 2007). Here, we report the unusual genetic behavior of a quantitative gain-of-function CNGC mutation (brush) in Lotus japonicus resulting in a leaky tetrameric channel. brush resides in a cluster of redundant CNGCs encoding subunits which resemble metazoan voltage-gated potassium (Kv1-Kv4) channels in assembly and gating properties. The recessive mongenic brush mutation impaired root development and infection by nitrogen-fixing rhizobia. The brush allele exhibited quantitative behavior since overexpression of the cluster subunits was required to suppress the brush phenotype. The results reveal a mechanism by which quantitative competition between channel subunits for tetramer assembly can impact the phenotype of the mutation carrier.

Celebrating 20 Years of Genetic Discoveries in Legume Nodulation and Symbiotic Nitrogen Fixation

“…An unknown calcium pump and the known calcium channels (CNGCa/b/c) are believed to work in concert to generate nuclear calcium spiking (Charpentier et al, 2016). A gainof-function mutation in LjBRUSH, another CNGC gene, impairs rhizobial infection but only at high temperatures (Maekawa-Yoshikawa et al, 2009;Chiasson et al, 2017). Analysis of other Nod2 mutants revealed that the nuclear calcium-calmodulin kinase MtDMI3/CCaMK acts as an intermediary between Nod factor perception and nodule development (Gleason et al, 2006;Tirichine et al, 2006), presumably as a sensor of the signal encoded in nuclear calcium spiking.…”

Multiple cyclic nucleotide‐gated channels coordinate calcium oscillations and polar growth of root hairs

“…Similar to the results from GFP‐localization studies, the fluorescent signals for the homomeric CNGC9 combination were also detected in the ER (Figure S2b). Although the fluorescence signals observed in heteromeric BiFC combinations do not prove that heteromeric channel assembly has occurred, the possibility that CNGCs promiscuously interact with each other in the plasma membrane was previously reported for other members of the plant CNGC family (Chiasson et al ., ).…”

“…Thus, RBOHC and ROS formations are not necessarily essential for generating the calcium gradient (Monshausen et al ., ). Obviously, CNGCs expressed in heterologous systems do not require elevated ROS levels (Gao et al ., , ; Wang et al ., ; Chiasson et al ., ; Zhang et al ., ). The single, double and triple cngc mutants generated in this study therefore enable the study of this regulatory feedback loop in more detail.…”

“…Plant CNGCs are related to cyclic nucleotide‐gated (CNG) channels, as well as to hyperpolarization‐activated (HCN) channels, which are modulated but not gated by cyclic nucleotides, operating as functional tetramers with a fixed stoichiometric composition (Kaupp and Seifert, ; Biel et al ., ; Cukkemane et al ., ). CNGCs serve as voltage‐dependent Ca 2+ ‐permeable channels (Leng et al ., ; Gao et al ., ; Chiasson et al ., ; Zhang et al ., ). Calmodulin (CaM) can serve as an intrinsic Ca 2+ sensor associated with the C terminus of many CNGCs (Fischer et al ., , ), and Ca 2+ ‐dependent CaM binding to the N terminus provides an additional layer of CNGC regulation (DeFalco et al ., ).…”

Natural variation identifies aPxygene controlling root vascular organization and formation of nodules and lateral roots inLotus japonicus

“…In subsequent steps NFR5 interacts with the SYMRK LRR receptor and a cytoplasmic kinase NiCK4 that accelerates downstream signaling 5,6 . Further downstream in the symbiosis pathway operating in Lotus and/or Medicago truncatula (Medicago), nucleoporins (NUP85, NUP133, and NENA), cation channels (CASTOR and POLLUX) and calcium channels (CNGC) are involved in releasing the perinuclear calcium spiking [7][8][9][10][11][12][13][14] . This calcium fluctuation is recorded by calcium calmodulin-dependent protein kinases (CCaMK) [15][16][17][18] , and activated CCaMK phosphorylates the CYCLOPS transcription factor [19][20][21][22] .…”