Exogenous Sorbitol Modifies Sugar Metabolism, Transport and Signalling in In Vitro-Grown ‘Myrobalan 29C’ According to Tissue

Sugars regulate many aspects of plant growth and development and recently are referred to as phytohormone-like plant growth regulators. Thus, the present study aimed (i) to investigate the effect of sorbitol on growth parameters and (ii) to understand sugar signalling through the transcriptional activation/repression of sugar metabolism-associated genes, enzyme activity and their associated sugar content in in vitro-grown ‘Myrobalan 29C’. For this, explants were cultivated in Murashigue and Skoog medium with 30 g L −1 sucrose (control plants) or sorbitol (15, 30 and 60 g L −1 ). After 30 days, the explants were sectioned into two parts, by separating the base from the apex. The responses to sorbitol treatment were related to the concentration and type of tissue evaluated. Sorbitol treatment (30 g L −1 ) positively affected growth parameters. Sorbitol induces the expression of a variety of sugar metabolism-related genes, whose expression pattern was down- and upregulated in apical and basal tissue, respectively. High sugar availability in apical tissue inactivated Sucrose non-fermenting-1 (SNF1)-related kinase 1 (SnRK1) to support growth and to maintain energy homeostasis. Besides, SnRK1 may positively interact with Hexokinase 1 (HXK1). In conclusion, our results showed the role of sorbitol as an exogenous source of carbon on sugar metabolism in in vitro-grown ‘Myrobalan 29C’ in basal–apical leaf tissue (source–sink) and they could potentially provide new avenues for large-scale in vitro propagation. Future studies may focus in establish an interplay among SnRK1/Target of rapamycin (TOR)/HXK1 and sugar signal (Trehalose-6-phosphate, sucrose, glucose, and sorbitol) in “usual sorbitol producers” species.