Transcriptome profiling of Rehmannia glutinosa uncovers ABA/GA antagonism mechanisms in tuberous root initiation

Rehmannia glutinosa tuberous roots are the critical determinant of its medicinal and economic values. The swelling of its adventitious roots is a prerequisite for tuberous roots initiation, which is antagonistically regulated by abscisic acid (ABA) and gibberellins (GA). However, the antagonistic mechanisms between ABA and GA remain poorly understood. In this study, exogenous ABA significantly promoted adventitious roots swelling, whereas GA exerted an inhibitory effect. To investigate the potential mechanisms, transcriptome analysis was carried out on R. glutinosa roots treated with ABA or GA. Compared to control samples, 7,416 differentially expressed genes (DEGs) (ABA) and 9,034 DEGs (GA) were identified in adventitious roots. The expression patterns of DEGs involved in ABA or GA metabolism and signal transduction revealed the dynamic regulation of ABA/GA equilibrium. Kyoto Encyclopedia of Genes and Genomes and Gene set enrichment analysis showed enhanced starch accumulation and cell wall biosynthesis and modification in ABA-treated adventitious roots. The lignification induced by GA and key regulators in the antagonistic action of ABA and GA, including DREBs, ERFs and PERs, were identified using weighted gene co-expression network analysis and protein-protein interaction network analysis. And the transient expression analysis of RgERF017 and RgPER10 in tobacco further demonstrated that these two genes are involved in ABA/GA antagonism through the control of ABA and GA metabolism. This study provides a comprehensive analysis of the antagonistic regulatory network between ABA and GA during R. glutinosa tuberous roots initiation, deepening our understanding of the molecular mechanisms underlying tuberous root formation.