The Second Site Modifier, Sympathy for the ligule, Encodes a Homolog of Arabidopsis ENHANCED DISEASE RESISTANCE4 and Rescues the Liguleless narrow Maize Mutant

Abstract

Liguleless narrow1 encodes a plasma membrane-localized receptor-like kinase required for normal development of maize (Zea mays) leaves, internodes, and inflorescences. The semidominant Lgn-R mutation lacks kinase activity, and phenotypic severity is dependent on inbred background. We created near isogenic lines and assayed the phenotype in multiple environments. Lgn-R plants that carry the B73 version of Sympathy for the ligule (Sol-B) fail to grow under hot conditions, but those that carry the Mo17 version (Sol-M) survive at hot temperatures and are significantly taller at cool temperatures. To identify Sol, we used recombinant mapping and analyzed the Lgn-R phenotype in additional inbred backgrounds. We identified amino acid sequence variations in GRMZM2G075262 that segregate with severity of the Lgn-R phenotypes. This gene is expressed at high levels in Lgn-R B73, but expression drops to nonmutant levels with one copy of Sol-M. An EMS mutation solidified the identity of SOL as a maize homolog of Arabidopsis (Arabidopsis thaliana) ENHANCED DISEASE RESISTANCE4 (EDR4). SOL, like EDR4, is induced in response to pathogen-associated molecular patterns such as flg22. Integrated transcriptomic and phosphoproteomic analyses suggest that Lgn-R plants constitutively activate an immune signaling cascade that induces temperature-sensitive responses in addition to defects in leaf development. We propose that aspects of the severe Lgn-R developmental phenotype result from constitutive defense induction and that SOL potentially functions in repressing this response in Mo17 but not B73. Identification of LGN and its interaction with SOL provides insight into the integration of developmental control and immune responses.

Genome assembly of the Chinese maize elite inbred line RP125 and its EMS mutant collection provide new resources for maize genetics research and crop improvement

“…Large mutant collections will facility cloning of new genes cloning and accelerate biological research in maize. To date, mutant populations have only been developed in a few maize varieties (Anderson et al., 2019; Liang et al., 2019; Lu et al., 2018; Marcon et al., 2020; McCarty et al., 2005; Tran et al., 2020; Till et al., 2004). However, the same mutant can have distinct phenotypes in different genetic backgrounds due to the presence of natural modifiers (Anderson et al., 2019; Wu et al., 2020).…”

“…To date, mutant populations have only been developed in a few maize varieties (Anderson et al., 2019; Liang et al., 2019; Lu et al., 2018; Marcon et al., 2020; McCarty et al., 2005; Tran et al., 2020; Till et al., 2004). However, the same mutant can have distinct phenotypes in different genetic backgrounds due to the presence of natural modifiers (Anderson et al., 2019; Wu et al., 2020). For example, both the liguleless and autoimmunity phenotypes of Liguleless narrow ( Lgn ) mutants are suppressed in the Mo17 background (Anderson et al., 2019).…”

“…These mutant collections provide the community with valuable resources for gene function studies. However, due to the high genetic diversity of maize, the same mutants frequently exhibit distinct phenotypes in different genetic backgrounds (Anderson et al., 2019; Wu et al., 2020). Therefore, a high‐quality genome combined with a mutant collection in a distinct background will facilitate novel discoveries and the isolation of desirable allelic variants for basic research and breeding.…”

Maize Introgression Library Provides Evidence for the Involvement ofliguleless1in Resistance to Northern Leaf Blight

“…A plant architecture QTL in maize was recently dissected (Tian et al 2019) that regulates BR and leaf angle, increasing yield in dense population environments, and demonstrated the involvement of LG1 in the regulation of genes controlling these traits. The sympathy for the ligule gene, a modifier of the liguleless narrow1 gene, was also shown to have a pleiotropic role in maize leaf architecture and disease resistance (Anderson et al 2019). The observation of both positive and negative correlations between leaf angle and NLB (AUDPC) in the five and four RIL families of the NAM population, respectively, suggests that lg1 may be multi-allelic, may have a role in leaves that is distinct from its role in leaf angle, and that lg1 influences pathogenesis.…”

Maize nested introgression library provides evidence for the involvement ofliguleless1in resistance to northern leaf blight

“…Recently, Tian et al (2019) dissected a plant architecture QTL that regulates BR and leaf angle, increasing yield in dense population environments, and demonstrated the involvement of LG1 in the regulation of genes controlling these traits. The sympathy for the ligule gene, a modifier of the liguleless narrow1 gene, was also shown to have a pleiotropic role in leaf architecture and disease resistance (Anderson et al, 2019). The observation of both positive and negative correlations between leaf angle and NLB (AUDPC) in the five and four RIL families of the NAM population, respectively, suggests that lg1 may be multi-allelic, and may have a role in leaves that is distinct from its role in leaf angle and that influences pathogenesis.…”