JRE4 is a master transcriptional regulator of defense-related steroidal glycoalkaloids in tomato.

Steroidal glycoalkaloids (SGAs) are specialized anti-nutritional metabolites that accumulate in Solanum lycopersicum (tomato) and Solanum tuberosum (potato). A series of SGA biosynthetic genes is known to be upregulated in Solanaceae species by jasmonate-responsive Ethylene Response Factor transcription factors, including JRE4 (otherwise known as GAME9), but the exact regulatory significance in planta of each factor has remained unaddressed. Here, via TILLING-based screening of an EMS-mutagenized tomato population, we isolated a JRE4 loss-of-function line that carries an amino acid residue missense change in a region of the protein important for DNA binding. In this jre4 mutant, we observed downregulated expression of SGA biosynthetic genes and decreased SGA accumulation. Moreover, JRE4 overexpression stimulated SGA production. Further characterization of jre4 plants revealed their increased susceptibility to the generalist herbivore Spodoptera litura larvae. This susceptibility illustrates that herbivory resistance is dependent on JRE4-mediated defense responses, which include SGA accumulation. Ethylene treatment attenuated the jasmonate-mediated JRE4 expression induction and downstream SGA biosynthesis in tomato leaves and hairy roots. Overall, this study indicated that JRE4 functions as a primary master regulator of SGA biosynthesis, and thereby contributes toward plant defense against chewing insects.

Intestinal Anti-Inflammatory Activity of Perillaldehyde.

Monoterpenoid perillaldehyde (PA) is the major component in Perilla frutescens leaf essential oil, but its function regarding anti-inflammatory effect is unclear. We explored the anti-inflammatory activity of PA in a dextran sulfate sodium (DSS)-induced colitis mouse model using relief of bodyweight loss (avg. 49.2% mitigation; P = 0.094) and colon damage (avg. 35.3% mitigation; P < 0.05) by administration of PA at a 100 mg/kg dosage. The PA administration resulted in suppression of DSS-induced expression of pro-inflammatory cytokine genes and matrix metalloproteinase-9 in the colon (e.g., avg. 60.6% mitigation for TNF-α mRNA levels; P < 0.05). These effects were confirmed in macrophage RAW264.7 cells stimulated with lipopolysaccharide (LPS). Application of PA induced cell suppression of LPS-induced expressions of genes and proteins of pro-inflammatory cytokines and induced activation of c-Jun N-terminal kinases (JNKs, p54 and p46; P < 0.05) but not nuclear factor-κB p65. The half maximal inhibitory concentration for decreased expression levels of TNF-α mRNA was 171.7 µM. We discuss the in vivo function of PA in amelioration of intestinal inflammation via JNK-mediated cytokine regulation.