Effects of ABA, auxin, and gibberellin on the expression of genes for vacuolar H +-inorganic pyrophosphatase, H +-ATPase subunit A, and Na +/H + antiporter in barley

Abstract

We analyzed the effects of ABA, auxin, and gibberellin on the expression of two genes ( HVP1 and HVP10) for vacuolar H +-inorganic pyrophosphatase (EC 3.6.1.1) and one ( HvVHA-A) for the catalytic subunit (subunit A) of vacuolar H +-ATPase (EC 3.6.1.3) by quantification of the transcript levels, to identify the hormones responsible for regulating the expression of these genes in barley ( Hordeum vulgare L.) in response to environmental changes such as salt stress. ABA markedly induced the expression of HVP1 and slightly increased the expression of HVP10 and HvVHA-A. In contrast, 2,4-D only increased the expression of HVP1, and GA 3 had no significant effects on any gene. The maximum level of HVP1 transcripts in response to these hormones was also much higher than the levels of HVP10 and HvVHA-A transcripts. In addition, we also analyzed the expression of one gene ( HvNHX1) for vacuolar Na +/H + antiporter, and HvNHX1 expression changed in a pattern similar to that of the HVP1 expression. Furthermore, treatment with ABA and 2,4-D increased Na +/H + antiport activity and proton-translocating activities by H +-PPase and H +-ATPase in tonoplast vesicles, and treatment with ABA also increased the amount of V-PPase protein of tonoplast vesicles. These results suggest that the hormones ABA and 2,4-D regulate the expression of the H +-pump and Na +/H + antiporter genes and are thus important effectors that regulate the expression of HVP1and HvNHX1.