Changes in cytokinin metabolism in a small fruit mutant of 'Hiratanenashi' persimmon (Diospyros kaki Thunb.)

I. Naito, S. Nishiyama, M. Gao-Takai, H. Yamane, R. Tao
The fruit size is one of the most important traits affecting the economic value of persimmon (Diospyros kaki Thunb.) fruit. To elucidate the regulatory mechanism underlying fruit size in persimmon, we investigated the cytokinin metabolism in a small-fruit somaclonal mutant 'Totsutanenashi' (TTN), a bud sport of the leading Japanese cultivar 'Hiratanenashi' (HTN). We previously reported that the number of parenchyma cells in the early growing stage is less in TTN fruit than in HTN fruit, and that artificial cytokinin (N-(2-chloro-4-pyridyl)-N'-phenylurea, CPPU) treatment of developing fruit could restore the fruit size of TTN. In this study, we investigated the expression levels of genes involved in cytokinin biosynthesis, D. kaki ISOPENTENYL TRANSFERASE1 (DkIPT1) and D. kaki LONELY GUY1 (DkLOG1), and cell cycle regulation, D. kaki CYCLIN D1 (DkCyCD1) throughout fruit development using real-time PCR. DkIPT1, DkLOG1, and DkCyCD1 had higher expression levels in HTN fruit than in TTN fruit, especially during the early growing stage. We have also dertermined that the cytokinin (N6-(Δ2-isopentenyl) adenine, iP; iP riboside, iPR; trans-zeatin, tZ; tZ riboside, tZR) levels were higher in HTN fruit than in TTN fruit. These results are consistent with our previous transcriptome analysis showing that the cell cycle and its regulatory pathways appeared to be affected by this mutation. Taken together, these results suggest that the reduced expression of cytokinin metabolism-related genes affects the fruit size in TTN through suppressed cell division activity.
Naito, I., Nishiyama, S., Gao-Takai, M., Yamane, H. and Tao, R. (2018). Changes in cytokinin metabolism in a small fruit mutant of 'Hiratanenashi' persimmon (Diospyros kaki Thunb.). Acta Hortic. 1208, 245-250
DOI: 10.17660/ActaHortic.2018.1208.32
fruit size, cytokinin, cell division, bud sport, next generation sequencing, qPCR

Acta Horticulturae