Soil salinity is one of the major abiotic stresses affecting seed germination, crop growth and productivity. In this study, seeds of three wheat (Triticum aestiveum L.) and three barley (Hordeum vulgare L.) cultivars were treated with different concentrations of NaCl to investigate the effect of salt on seed germination physiology and metabolism through the characterization of seed germination pattern, gamma-aminobutyric acid (GABA) shunt metabolite accumulation [GABA, glutamate (Glu) and alanine (Ala)] and glutamate decarboxylase (GAD) expression using RT-PCR. A trend of decreasing germination percentage with increasing NaCl concentrations was observed. Under all salt stress treatments, data showed significant increase with positive correlation (r = 0.50–0.99) between abundance of GABA shunt metabolites and salt concentration in all wheat and barley cultivars for 5 days. Increased GABA content was associated with a small but significant increase in Ala and Glu content in all cultivars. In all NaCl treatments, the transcription of GAD in terms of RNA abundance showed a significant increase in all cultivars with positive correlation (r = 0.50–0.98). Data showed significant association between GAD RNA transcription and the response of germinating seeds to salt stress in terms of GABA shunt metabolite accumulation. The elevated expression of GAD under salinity suggests the need for elevated activity of the GAD-mediated conversion of Glu to GABA during seed germination, which provides alternative metabolic routes to the respiratory machinery, balancing carbon and nitrogen metabolism and osmolyte synthesis in germinating seeds of wheat and barley under salt stress.

The neuromuscular systems of parasitic helminths are targets that are particularly amenable for anthelmintics. In this study, we describe a GABAergic neurotransmission in adult Schistosoma mansoni, the trematode responsible for high levels of morbidity in people living in developing countries. GABA immunoreactivity (GABA-IR) was detected in nerve cells and fibres of the cerebral ganglia and longitudinal nerve cords and the nerve plexuses ramifying throughout the parenchyma of male adult worms. In addition, strong GABA-IR was also found associated with the oral and ventral suckers as well as in testes indicating a role for GABA in fixation to the host vascular wall and spermatogenesis. The capacity to synthesize GABA from glutamate was confirmed by measurement of a glutamate decarboxylase (GAD) activity. Supporting these data, a single band with an apparent molecular weight of about 67 kDa was detected using an antibody raised against mammalian GAD. In vivo studies revealed that picrotoxin, a non-competitive antagonist of the GABAA receptor, produced a modification of the motility and locomotory behaviour of adult worms, suggesting that GABAergic signalling pathway may play a physiological role in the motonervous system of S. mansoni and could be considered as a potential target for the development of new drugs.