Auxin is one of the most important phytohormones involved in plant growth and development. Here, we identified a total of 26 Aux/IAA genes displaying high sequence identity within the conserved domains I, II, III, and IV by screening the grapevine genome proteome 129 database. The Vitis vinifera Aux/IAA proteins can be classified into two groups (A and B) on the basis of their phylogenetic relationships. A search for cis-regulatory elements in the promoter sequences of VvAux/IAA genes revealed that the majority of these proteins may be regulated by light, phytohormones, and abiotic stresses. We also report the isolation and expression analysis of the cDNA of VvAux/IAA4, the most highly expressed VvAux/ IAA gene from V. vinifera cv. Sultanine, according to ESTs in the NCBI database. The VvAux/IAA4 gene contains a full-length open reading frame of 1,080 bp, and its predicted amino acid sequence is highly similar to those of Aux/IAA proteins from other plants, including the presence of an AuxIAA/ARF dimerization motif in the C-terminal region. The expression of VvAux/IAA4 was found to be elevated during berry development, and slowly decrease from the initiation of ripening to the overripening stage. VvAux/IAA4 was highly expressed in young leaves and roots, and expressed at low levels in pollen and tendrils. Finally, the expression of VvAux/IAA4 was rapidly induced in response to NAA treatment, but was decreased by salt, drought, and SA treatments. Our results provide evidence of crosstalk between phytohormone and abiotic stresses, and support a role for auxin in stress responses.
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Pineal hormone melatonin is proposed as a potential treatment for severe sleep disturbances, and various gastrointestinal disorders. It was shown that melatonin increases intestinal motility and influences the activity of myoelectric complexes of the gut. The aim of the study was to evaluate the mechanisms of the effect of exogenous melatonin on gastric emptying rate. Male Sprague-Dawley rats were fitted with gastric cannulas under anesthesia. The rate of gastric emptying of saline was determined after instillation into the gastric fistula, from the volume and phenol red concentrations recovered after 5 min. Melatonin injected intraperitoneally (ip; 0.001-100 mg/kg) delayed gastric emptying rate of saline at 3 and 10 mg/kg doses. When administered ip 15 min before melatonin (10 mg/kg) injections, CCK2 (L-365,260, 1 mg/kg) or 5-HT3 receptor (ramosetrone, 50 µg/kg) blockers abolished melatonin-induced delay in gastric emptying rate, while the blockade of sympathetic ganglia (bretylium tosylate, 15 mg/kg) significantly reduced the delay in gastric emptying rate. CCK1 receptor blocker (L-364,718, 1 mg/kg) had no significant effect on the delaying action of melatonin. Our results indicate that pharmacological doses of melatonin delay gastric emptying via mechanisms that involve CCK2 and 5-HT3 receptors. Moreover, it appears that exogenous melatonin inhibits gastric motility in part by activating sympathetic neurons.
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