The ell1 mutation disrupts tryptophan metabolism and induces cell death.

Tryptophan metabolism pathways are important components of the plant immune system; for example, serotonin is derived from tryptophan, and plays a vital role in rice (Oryza sativa) innate immunity. Recently, we isolated a rice mutant, early lesion leaf 1 (ell1), which exhibits lesions. RNA-seq analysis revealed that KEGG pathways related to amino acid metabolism were significantly enriched in the transcripts differentially expressed in this mutant. Furthermore, measurements of free amino acid contents revealed the accumulated tryptophan of ell1 mutant. In addition, the transcript levels of genes related to tryptophan biosynthesis were significantly enhanced in the ell1 mutant. These results revealed that ELL1 plays a critical role in tryptophan metabolism. Based on these findings, it is revealed that loss of ELL1 function may disrupt tryptophan metabolism, thereby inducing cell death and forming lesions in rice.