The Arabidopsis trehalose-6-P synthase AtTPS1 gene is a regulator of glucose , abscisic acid , and stress signaling . In Arabidopsis ( Arabidopsis thaliana ) , trehalose is present at almost undetectable levels , excluding its role as an osmoprotectant . Here , we report that overexpression of AtTPS1 in Arabidopsis using the 35S promoter led to a small increase in trehalose and trehalose-6-P levels . In spite of this , transgenic plants displayed a dehydration tolerance phenotype without any visible morphological alterations , except for delayed flowering . Moreover , seedlings overexpressing AtTPS1 exhibited glucose ( Glc ) - and abscisic acid ( ABA ) - insensitive phenotypes . Transgenic seedlings germinated on Glc were visibly larger with green well - expanded cotyledonary leaves and fully developed roots , in contrast with wild - type seedlings showing growth retardation and absence of photosynthetic tissue . An ABA dose - response experiment revealed a higher germination rate for transgenic plants overexpressing AtTPS1 showing insensitive germination kinetics at 2.5 mum ABA . Interestingly , germination in the presence of Glc did not trigger an increase in ABA content in plants overexpressing AtTPS1 . Expression analysis by quantitative reverse transcription - PCR in transgenic plants showed up - regulation of the ABI4 and CAB1 genes . In the presence of Glc , CAB1 expression remained high , whereas ABI4 , HXK1 , and ApL3 levels were down - regulated in the AtTPS1 - overexpressing lines . Analysis of AtTPS1 expression in HXK1 - antisense or HXK1 - sense transgenic lines suggests the possible involvement of AtTPS1 in the hexokinase - dependent Glc - signaling pathway . These data strongly suggest that AtTPS1 has a pivotal role in the regulation of Glc and ABA signaling during vegetative development .