Downregulation of a cluster of genes encoding nitrate transporter 1/peptide transporter family proteins in tomato with a mutated JRE4 transcription factor

A group of anti-nutritional specialized metabolites called steroidal glycoalkaloids (SGAs) are produced in Solanum species such as tomato, potato, and eggplant. The transcription factor JASMONATE-RESPONSIVE ETHYLENE RESPONSE FACTOR 4 (JRE4) regulates many SGA biosynthesis genes in tomato and potato. Here we report that the expression of a cluster of genes encoding nitrate transporter 1/peptide transporter family (NPF) members is downregulated in the jre4-1 loss-of-function tomato mutant, which has a low-SGA phenotype compared to the wild type. NPFs are a large family of plant membrane transporters that transport a wide range of substrates, including specialized metabolites. We found that the JRE4-regulated NPF genes are induced by the defense-related phytohormone jasmonate. Conversely, jasmonate-mediated induction of gene expression was attenuated by ethylene treatment of the leaves. The co-regulation of the NPF genes with SGA biosynthesis genes by JRE4 suggests that NPF transporters are involved in the SGA pathway.

Automated summary

A group of specialized metabolites called steroidal glycoalkaloids (SGAs) are produced in Solanum species and their biosynthesis is regulated by the transcription factor JASMONATA-RESPONSIVE ETHYLENE RESPONSE FACTOR 4 (JRE4). In this study, the downregulation of a cluster of genes encoding nitrate transporter 1/peptide transporter family (NPF) members was observed in a low-SGA tomato mutant with a loss-of-function mutation in JRE4. The NPF transporters, which belong to a large family of plant membrane transporters, are induced by the defense-related phytohormone jasmonate and are potentially involved in the SGA pathway.