Abstract
ABSTRACTThe effects of silicon (Si) and salicylic acid (SA) applications on proline content and expression of Δ1-pyrrolin-5-carboxylate synthetase (P5CS) were examined under different drought levels and different drought exposure times. Two wheat cultivars, a drought tolerant and a drought sensitive were used. The experiment was a factorial based on completely randomized design with three replicates. Expression analysis by the quantitative real time PCR showed that the tolerant cultivar had significantly higher P5CS expressions compared to the sensitive one under drought stress. In sampling time points, the maximum level of mRNA was observed at 48 h after stress was applied. At 48 h after stress induction, the expression of P5CS was almost 3.1 fold higher in the tolerant cultivar compared to the sensitive one. In both cultivars, gene expression decreased from 48 to 72 h. The stressed plants treated with Si + SA showed a higher expression. Proline content started to increase by Si and SA treatments and the maximum proline content was obtained at simultaneous application of Si + SA. Drought stress significantly reduced chlorophyll content, relative water content and leaf water potential of both cultivars, while increased electrolyte leakage (EL) of the leaves. In contrast, foliar-applied Si and SA significantly increased these parameters and reduced EL, and the effect of simultaneous application of Si and SA was greater. The results suggest that the P5CS is a stress inducible gene. This gene has the potential to be used for improvement of drought stress tolerance in wheat. Network analysis highlighted positive interaction of osmotic stress, drought and cold stress on P5CS1 and the regulatory role of MYB2, ERF-1, and EIN3 transcription factors. In conclusion, alleviation of drought stress by application of Si and SA was associated partially with enhanced expression of P5CS gene and following proline accumulation.
Highlights
Wheat (Triticum aestivum L.) is an important food crop grown all over the world
In comparison to proline content and expression of Δ1pyrrolin-5-carboxylate synthetase (P5CS) expression, proline content started to increase by Si and salicylic acid (SA) treatment and the maximum proline content was obtained at simultaneous application of Si + SA (Figure 2)
The results of this study highlighted the P5CS gene expression was significantly higher in the stressed plants, especially, when treated by Si + SA
Summary
Wheat (Triticum aestivum L.) is an important food crop grown all over the world. Wheat productivity is hampered due to a variety of abiotic stresses such as drought, salinity, and heat (Costa et al 2011). Under semi-arid climatic conditions, wheat is usually exposed to drought stress periods during the growing season (Dhanda et al 2004). A major component of drought tolerance is the production and accumulation of osmotically active substances, known as osmoregulation (Reddy et al 2004; Zhu et al 2005). Osmoregulation, which involves maintenance of cell turgor or volume by accumulation of solutes, is a significant adaptation mechanism under water stress conditions (Hummel et al 2010). Several plants modify their metabolism under water deficit by accumulating proline, soluble carbohydrates, organic acids, and amino acids (Lobato et al 2009). Previous studies have suggested that proline accumulation contributes to increase osmotic stress tolerance
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