Neurospora crassa ncs-1, mid-1 and nca-2 double-mutant phenotypes suggest diverse interaction among three Ca2 + -regulating gene products

Abstract

The calcium (Ca2+) signalling system in the filamentous fungus Neurospora crassa is unique and significantly different from that in plants and animals, mainly with regard to the second messenger systems involved in Ca2+-release from internal stores (Galagan et al. 2003). The complex Ca2+ signalling system in N. crassa contains 48 Ca2+ signalling proteins including a Ca2+ and/or CaM binding protein called neuronal calcium sensor-1 (NCS-1), a Ca2+-permeable channel MID-1 and a PMCA-type Ca2+-ATPase NCA-2 (Zelter et al. 2004; Tamuli et al. 2013). Here, we show that ncs-1, mid-1 and nca-2 interactions affect growth, carotenoid accumulation, Ca2+ stress tolerance, ultraviolet (UV) survival and circadian-regulated conidiation in N. crassa. The N. crassa homologue of NCS-1 has a role in growth, Ca2+ stress tolerance and UV survival (Deka et al. 2011; Tamuli et al. 2011). MID-1 is necessary for Ca2+homeostasis in N. crassa (Lew et al. 2008). Mid-1 in Gibberella zeae has a role in growth, development and ascospore discharge (Cavinder et al. 2011). NCA-2 is responsible for adaptation to stress conditions and functions to pump Ca2+ out of the cell in N. crassa (Benito et al. 2000; Bowman et al. 2011). In Schizosaccharomyces pombe, Ncs1p, the homologue of NCS-1, promotes Ca2+-induced closure of Yam8p Ca2+ channel, a homologue of the MID1 (Hamasaki-Katagiri and Ames 2010). The Ca2+-sensitive phenotype of the ncs1 deletion mutant is rescued by a yam8 deletion, indicating that Ncs1p negatively regulates Yam8p in S. pombe