Transcriptomic and Anatomic Profiling Reveal Etiolation Promotes Adventitious Rooting by Exogenous Application of 1-Naphthalene Acetic Acid in Robinia pseudoacacia L.

Abstract

The process of etiolation contributes significantly to vegetative propagation and root formation of woody plants. However, the molecular interaction pattern of different factors for etiolated adventitious root development in woody plants remains unclear. In the present study, we explored the changes at different etiolation stages of adventitious root formation in Robinia pseudoacacia. Histological and transcriptomic analyses were performed for the etiolated lower portion of hypocotyls to ascertain the adventitious root responses. We found that the dark-treated hypocotyls formed roots earlier than the control. Exogenous application of NAA (0.3 mg/L) stimulated the expressions of about 310 genes. Among these, 155 were upregulated and 155 were downregulated. Moreover, differentially expressed genes (DEGs) were significantly enriched in multiple pathways, including the biosynthesis of secondary metabolites, metabolic pathway, plant hormone signal transduction, starch and sucrose metabolism, phenylpropanoid biosynthesis, and carbon metabolism. These pathways could play a significant role during adventitious root formation in etiolated hypocotyls. The findings of this study can provide novel insights and a foundation for further studies to elucidate the connection between etiolation and adventitious root formation in woody plants.