Potential herbicide target, 7-keto-8-aminopelargonic acid synthase.

The validation of potential herbicide target, 7-keto-8aminopelargonic acid synthase (KAPAS) in the early step of biotin biosynthesis pathway, was performed in vitro and in vivo with lead chemical triphenyltin acetate (TPTA). KAPAS activity was completely inhibited by TPTA with an IC50 of 19.85 μM. 40-day-old Arabidopsis thaliana plants were killed with foliar treatment of 125 g/ha TPTA under the greenhouse conditions. The germination of A. thaliana seeds was also completely inhibited with 62.5 μM TPTA, but it was rescued by 85– 92% with the supplement of biotin biosynthesis intermediates such as 0.5 mM of biotin, dethiobiotin, and 7, 8-diaminopelargonic acid, but not by 7-keto-8-aminopelargonic acid (KAPA). However, additional supplement of 0.5 mM S-adenosyl-L-methionine (SAM) with 0.5 mM KAPA rescued up to 91% of the germination previously inhibited by the 50 μM TPTA. Also, biotin supplements alleviated the growth inhibition of 40-day-old A. thaliana plant. Foliar application of TPTA induced 8-fold higher substrate (L-alanine) accumulation in the treated A. thaliana plants. RNA expression for KAPAS transcripts were much low in leaf tissue treated with TPTA. With these results, we report that SAM is an essential donor of amino groups for synthesis of the biotin precursor KAPA to 7, 8-diaminopelargonic acid (DAPA) synthesis in plants that KAPAS is a potential herbicidal target site in the biotin biosynthesis pathway, and that TPTA might be one of the potential non-comparative KAPAS inhibitors.