Treatment of potato tubers with the synthetic cytokinin 1-(α-ethylbenzyl)-3-nitroguanidine results in rapid termination of endodormancy and induction of transcripts associated with cell proliferation and growth

Perennial plants undergo repression of meristematic activity in a process called dormancy. Dormancy is a complex metabolic process with implications for plant breeding and crop yield. Endodormancy, a specific subclass of dormancy, is characteristic of internal physiological mechanisms resulting in growth suppression. In this study, we examine transcriptional changes associated with the natural cessation of endodormancy in potato tuber meristems and in endodormant tubers treated with the cytokinin analog 1-(alpha-ethylbenzyl)-3-niroguanidine (NG), which terminates dormancy. RNA-sequencing was used to examine transcriptome changes between endodormant and non-dormant meristems from four different harvest years. A total of 35,091 transcripts were detected with 2132 differentially expressed between endodormant and non-dormant tuber meristems. Endodormant potato tubers were treated with the synthetic cytokinin NG and transcriptome changes analyzed using RNA-seq after 1, 4, and 7 days following NG exposure. A comparison of natural cessation of dormancy and NG-treated tubers demonstrated that by 4 days after NG exposure, potato meristems exhibited transcriptional profiles similar to the non-dormant state with elevated expression of multiple histones, a variety of cyclins, and other genes associated with proliferation and cellular replication. Three homologues encoding for CYCD3 exhibited elevated expression in both non-dormant and NG-treated potato tissues. These results suggest that NG terminates dormancy and induces expression cell cycle-associated transcripts within 4 days of treatment.