Abstract
Jasmonates modulate many growth and developmental processes and act as stress hormones that play an important role in plant tolerance to biotic and abiotic stresses. Therefore, there is a need to identify the genes that are regulated through the jasmonate signalling pathway. Aquaporins, and among them the Tonoplast Intrinsic Proteins (TIPs), form the channels in cell membranes that are responsible for the precise regulation of the movement of water and other substrates between cell compartments. We identified the cis-regulatory motifs for the methyl jasmonate (MeJA)-induced genes in the promoter regions of all the HvTIP genes, which are active in barley seedlings, and thus we hypothesised that the HvTIP expression could be a response to jasmonate signalling. In the presented study, we determined the effect of methyl jasmonate on the growth parameters and photosynthesis efficiency of barley seedlings that had been exposed to different doses of MeJA (15–1000 µM × 120 h) in a hydroponic solution. All of the applied MeJA concentrations caused a significant reduction of barley seedling growth, which was most evident in the length of the first leaf sheath and dry leaf weight. The observed decrease of the PSII parameters after the exposure to high doses of MeJA (500 µM or higher) was associated with the downregulation of HvPsbR gene encoding one of the extrinsic proteins of the Oxygen Evolving Complex. The reduced expression of HvPsbR might lead to the impairment of the OEC action, manifested by the occurrence of the K-band in an analysis of fluorescence kinetics after MeJA treatment as well as reduced photosynthesis efficiency. Furthermore, methyl jasmonate treatment caused a decrease in the nitrogen content in barley leaves, which was associated with an increased expression the four tonoplast aquaporin genes (HvTIP1;2, HvTIP2;2, HvTIP4;1 and HvTIP4;2) predicted to transport the nitrogen compounds from the vacuole to the cytosol. The upregulation of the nitrogen-transporting HvTIPs might suggest their involvement in the vacuolar unloading of ammonia and urea, which both could be remobilised when the nitrogen content in the leaves decreases. Our research provides tips on physiological role of the individual TIP subfamily members of aquaporins under methyl jasmonate action.
Highlights
Jasmonates modulate many growth and developmental processes of plants including root, shoot and leaf growth, trichome and tuber formation, fruit ripening, leaf senescence pollen maturation and formation of secondary metabolites such as alkaloids and taxol [1,2,3]
We examined the effect of exogenous methyl jasmonate on the expression profiles of tonoplast intrinsic protein (TIP) genes in barley
To analyse the effect of exogenous methyl jasmonate (MeJA) on barley seedling growth and physiology, we applied a five-day treatment of spring barley cv
Summary
Jasmonates modulate many growth and developmental processes of plants including root, shoot and leaf growth, trichome and tuber formation, fruit ripening, leaf senescence pollen maturation and formation of secondary metabolites such as alkaloids and taxol [1,2,3]. Jasmonates act as stress hormones that play an important role in plant response to biotic and abiotic stresses [4,5,6]. Jasmonic acid and its derivates, such as jasmonyl isoleucine (JA-Ile), methyl jasmonate (MeJA) and other oxylipins, are collectively referred to as jasmonates [5] and among them MeJA was first isolated from the jasmine flower (Jasminum grandiflorum) [10]. The bioactive form in plants is represented by conjugate of JA with isoleucine (JA-lle) that acts as a ligand for JA receptor [11,12]. The biological activity of MeJA was only apparent when MeJA was converted to JA followed by its conjugation to JA-Ile [13]
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