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.