9.A.43.1.14
The accelerated cell death 6, ACD6, of 670 aas and 5 or 6 C-terminal TMSs. It is an activator of the defense response against virulent pathogens, including bacteria, fungi and oomycetes, that acts in a positive feedback loop with the defense signal salicylic acid (SA) (Lu et al. 2009). It regulates the salicylic acid (SA) signaling pathway leading to cell death and modulating cell fate (e.g. cell enlargement and/or cell division) (Lu et al. 2003). In response to SA signaling, it triggers the accumulation of the LRR receptor-like serine/threonine-protein kinase, (FLS2) at the plasma membrane, thus priming defenses (Zhang et al. 2014). Irt is involved in SA-dependent freezing signaling and tolerance (Miura and Ohta 2010). Information exchange between the ankyrin and transmembrane domains may be involved in activating defense signaling (Lu et al. 2005). It is an immune regulator in Arabidopsis (Chen et al. 2023). Two loci, MODULATOR OF HYPERACTIVE ACD6 1 (MHA1) and its paralog MHA1-LIKE (MHA1L), code for approximately 7 kDa proteins, which differentially interact with specific ACD6 variants. MHA1L enhances the accumulation of an ACD6 complex, thereby increasing the activity of the ACD6 standard allele for regulating plant growth and defenses. The intracellular ankyrin repeats of ACD6 are structurally similar to those found in mammalian ion channels. Several lines of evidence link increased ACD6 activity to enhanced calcium influx, with MHA1L as a direct regulator of ACD6, indicating that peptide-regulated ion channels are not restricted to animals (Chen et al. 2023).