These authors contributed equally to this work. SUMMARYJAsmonate ZIM-domain (JAZ) proteins repress the activity of transcription factors that execute responses to the plant hormone jasmonoyl-L-isoleucine (JA-Ile). The ZIM protein domain recruits the co-repressors NINJA and TOPLESS to JAZ-bound transcription factors, and contains a highly conserved TIF[F/Y]XG motif that defines the larger family of TIFY proteins to which JAZs belong. Here, we report that diverse plant species contain genes encoding putative non-TIFY JAZ proteins, including a previously unrecognized JAZ repressor in Arabidopsis (JAZ13, encoded by At3g22275). JAZ13 is most closely related to JAZ8 and includes divergent EAR, TIFY/ZIM, and Jas motifs. Unlike JAZ8, however, JAZ13 contains a Ser-rich C-terminal tail that is a site for phosphorylation. Overexpression of JAZ13 resulted in reduced sensitivity to JA, attenuation of wound-induced expression of JA-response genes, and decreased resistance to insect herbivory. JAZ13 interacts with the bHLH transcription factor MYC2 and the co-repressor TOPLESS but, consistent with the absence of a TIFY motif, neither NINJA nor other JAZs. Analysis of single and higher-order T-DNA insertion jaz null mutants provided further evidence that JAZ13 is a repressor JA signaling. Our results demonstrate that proteins outside the TIFY family are functional JAZ repressors and further suggest that this expansion of the JAZ family allows fine-tuning of JA-mediated transcriptional responses.

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.

Glandular trichomes are epidermal structures that provide a first line of chemical defense against arthropod herbivores and other biotic threats. The most conspicuous structure on leaves of cultivated tomato (Solanum lycopersicum) is the type-VI glandular trichome (tVI-GT), which accumulates both flavonoids and volatile terpenoids. Although these classes of specialized metabolites are derived from distinct metabolic pathways, previous studies with a chalcone isomerase 1 (CHI1)-deficient mutant called anthocyanin free (af) showed that flavonoids are required for terpenoid accumulation in tVI-GTs. Here, we combined global transcriptomic and proteomic analyses of isolated trichomes as a starting point to show that the lack of CHI1 is associated with reduced levels of terpenoid biosynthetic transcripts and enzymes. The flavonoid deficiency in af trichomes also resulted in the upregulation of abiotic stress-responsive genes associated with DNA damage and repair. Several lines of biochemical and genetic evidence indicate that the terpenoid defect in af mutants is specific for the tVI-GT and is associated with the absence of bulk flavonoids rather than loss of CHI1 per se. A newly developed genome-scale model of metabolism in tomato tVI-GTs helped identify metabolic imbalances caused by the loss of flavonoid production. We provide evidence that flavonoid deficiency in this cell type leads to increased production of reactive oxygen species (ROS), which may impair terpenoid biosynthesis. Collectively, our findings support a role for flavonoids as ROS-scavenging antioxidants in glandular trichomes.