The 11th International Conference on Agricultural and Biological Sciences (ABS 2025)

Abstract: Shoot branching is an important trait in both agriculture and horticulture, as the number of axillary buds directly influences crop yield and seed production. Strigolactones (SLs) are a class of plant hormones that inhibit shoot branching in plants. In SL biosynthesis, carlactone, a biosynthetic precursor of SLs, is synthesized from β-carotene through sequential reactions catalyzed by the β-carotene isomerase DWARF27 (D27) and carotenoid cleavage dioxygenases 7 and 8 (CCD7 and CCD8). Carlactone is then converted to carlatonoic acid (CLA) via oxidation by cytochrome P450 encoded by the CYP711A gene family. CLA is further metabolized into various types of SLs. To date, more than 30 canonical and non-canonical SLs have been identified from various plants. However, the specific bioactive SLs for shoot branching inhibition remain unidentified. In our previous research, we collected SL biosynthesis mutants in the tomato cultivar Micro-Tom to evaluate the roles of SLs in tomato, but SL signaling mutants were not available. Bioactive SLs are perceived by DWARF14 (D14), a member of the α/β-fold hydrolase superfamily. Since bioactive phytohormones tend to accumulate in signaling mutants, we hypothesized that SLs involved in shoot branching inhibition might be enriched in sld14 mutants. Therefore, we generated sld14 mutants in Micro-Tom by genome editing. Our analysis revealed that 16-hydroxymethyl carlactonoate (16-HO-MeCLA) significantly accumulated in the nodes of the mutants compared to the wild type. We also found that CYP722A is associated with the 16-hydroxylation of CLA. 16-HO-MeCLA or the metabolites may serve as bioactive SLs. To further elucidate the physiological roles of 16-HO-MeCLA, we plan to investigate the function of the CYP722A gene.

Biography: Mikihisa UMEHARA is a Professor of Department of Biological Resources and Graduate School of Life Sciences, Toyo University, Japan. His major is plant physiology and plant biotechnology. He graduated from the University of Tsukuba in 1997, finished a doctor’s course at the Graduate School of Biological Sciences, the University of Tsukuba in 2004, and obtained Ph.D. in Science. He worked on onion breeding in Department of Biotechnology, Fukuoka Agricultural Research Center from 2004 to 2007. He joined RIKEN Plant Science Center as a special postdoctoral researcher in 2007 and worked on a class of plant hormones, strigolactones. In 2011, he moved to Toyo University as a associate professor, and became a full professor in 2015.