Exogenous spermine pretreatment confers tolerance to combined high-temperature and drought stressin vitroin trifoliate orange seedlings via modulation of antioxidative capacity and expression of stress-related genes

Abstract

Spermine (Spm) is thought to play an important role in drought or high-temperature (HT) tolerance. However, it is not clear whether Spm confers similar resistance in the presence of both drought and HT, which often occur simultaneously. In the present study, the trifoliate orange (Poncirus trifoliata (L.) Raf.) seedlings were pretreated with 1 mmol L−1 Spm to evaluate their tolerance to combined drought and HT (45 ºC) stress. Spm-pretreated seedlings showed less leaf wilting, less water loss and less electrolyte leakage than control leaves not treated with Spm within 180 min of treatment. Histochemical staining with diaminobenzidine and nitro blue tetrazolium showed that Spm-pretreated seedlings accumulated less hydrogen peroxide and superoxide than those of control plants 60, 120 and 180 min after treatment when exposed to both drought and HT (45 ºC). However, superoxide dismutase, peroxidase and catalase were significantly more active in Spm-pretreated seedlings than in control seedlings. In addition, Spm-pretreated seedlings showed significantly higher expression of heat shock proteins, abscisic acid (ABA)-responsive element binding factor and 9-cis-epoxycarotenoid dioxygenase 3 than controls either before (0 min) or after (60, 120 and 180 min) combined drought and HT treatment. All of these data suggest that exogenous Spm pretreatment confers tolerance to simultaneously occurring drought and HT stresses. Spm may influence this by activating antioxidant enzymes, increasing the effectiveness of scavenging of reactive oxygen species. It may also increase the expression levels of stress-related genes that protect trifoliate orange seedlings from stress damage.

Rhizobacterial Strain Bacillus megaterium BOFC15 Induces Cellular Polyamine Changes that Improve Plant Growth and Drought Resistance

“…Based on the data shown in this study, the inoculation with BOFC15 increased plant drought resistance, which contributed to the effects caused by microbe-induced increase in cellular PAs, including improved root systems, enhanced antioxidant enzymatic activities, and increased ABA content. These observations were consistent with the results reported by previous studies; in particular, high PA levels can directly promote root growth [ 34 ] and up-regulate antioxidant enzymatic activities under stress conditions [ 40 , 41 , 42 ]. Moreover, the inoculated plants exhibited higher ABA contents than the control plants under DS conditions.…”

“…A recent study has reported that PAs can form complexes with SOD, GPX, and CAT, for which these enzymes function more efficiently compared with their isolated enzymes [ 41 ]. Moreover, exogenous PAs have been shown to enhance the activities of antioxidant enzymes such as SOD and CAT under abiotic stress conditions [ 16 , 17 , 42 ]. Hence, BOFC15 mitigated drought-induced oxidative damage to plant cells via the activation of antioxidant systems, thereby regulating the ROS generation and redox status.…”

Speculation: Polyamines are important in abiotic stress signaling

“…Abscisic acid-responsive element binding factors (ABFs) are basic region/leucine zipper (bZIP) class transcription factors involved in the transcriptional regulation of abscisic acid-and/or stress-responsive genes via interaction with ABRE cis elements in their promoters. Trifoliate orange seedlings pre-treated with spermine had significantly higher expression of genes for heat shock proteins and ABFs than the control plants both under normal conditions and during combined drought and heat treatment [39]. Spermine has also been shown to induce certain enzymes, such as woundinduced protein kinase, and to be responsible for the post-translational activation of certain mitogen-activated protein kinases, such as salicylic acid-induced protein kinase.…”

Drought stress affects response of phytopathogen vectors and their parasitoids to infection‐ and damage‐induced plant volatile cues

“…Citrus is most often grown in warm climates with well-drained soils in areas that are subject to water deficit and that often require supplemental irrigation (Syvertsen & Garcia-Sanchez, 2014). Drought stress is an important feature in areas of citrus cultivation, including Spain (Gonzalez-Dugo et al, 2014), China (Fu et al, 2014), Australia (Staniford et al, 2009), South Africa (Dzikiti et al, 2011), and even Florida during autumn, and in cases of a relatively dry spring (Pérez-Pérez et al, 2007). Drought stress impacts citrus physiology by changing, for instance, amino acid and polyamine levels in leaves (Malik et al, 2014).…”