Osmotic stress affects polyamine homeostasis and phenolic content in proembryogenic liquid cell cultures of Scots pine

Abstract

Polyamines (PAs) are ubiquitous polycations involved in many physiological processes in plants, including somatic embryogenesis, cellular growth and stress reactions. In the present study, we focus on the consequences in PA metabolism caused by polyethylene glycol (PEG) in proembryogenic Scots pine (Pinus sylvestris L.) liquid cultures. The growth and viability of the cell masses and changes in PA concentrations and phenolic secondary metabolites were investigated under control, 5 and 10 % PEG treatments. The effect of osmotic stress responses was investigated at the gene expression level including stress, cell division, programmed cell death and PA-related genes and PA metabolites. Moreover, the expression of ethylene and proline biosynthesis genes and phenylalanine ammonia lyase and stilbene synthase (psSTS) was analyzed. Under osmotic stress conditions, we found a consistent pattern of endogenous PAs in Scots pine proembryogenic cells. However, accumulation of free spermine (Spm) and methyl putrescine under osmotic stress might indicate their specific role in stress protection. Expression of polyamine oxidase was down-regulated under osmotic stress, suggesting the role of PA catabolism in regulation of Spm levels. Scots pine proliferating proembryogenic cells are in a developmentally undifferentiated stage where the content of secondary metabolites is generally low. However, in the present study the total content of phenolic compounds increased but the biosynthesis of phenylpropanoids and stilbenes, generally considered as stress-protective molecules, was not affected by osmotic stress.

Coping with spring frost-effects on polyamine metabolism of Scots pine seedlings

“…Spring frost decreased expression of ADC, SPDS, ICE1 and LEA and the lower expression level of SPDS and ICE1 was maintained after the recovery in the needles. In our previous studies, we have shown that under drought or osmotic stresses various tissues are able to maintain consistent PA levels due to a downregulation PA catabolizing genes, which seems to be advantageous (Muilu-Mäkelä et al 2015a, 2015b. In the present study, the expression of PAO decreased in needles and roots after the recovery, which might be a consequence of the frost induced down-regulation of the PA biosynthesizing genes ADC and SPDS.…”

“…Dehydrins stabilize membranes (Koag et al 2009) and the accumulation of dehydrins in tissues in response to dehydrative stress enhances survival of Scots pine at low temperatures (Kontunen-Soppela et al 2000). Expression of catalase (CAT) is related to oxidative stress in Scots pine tissues (Vuosku et al 2015, Muilu-Mäkelä et al 2015b.…”

Establishment and Characterization of Callus and Cell Suspension Cultures of Selected Sorghum bicolor (L.) Moench Varieties: A Resource for Gene Discovery in Plant Stress Biology

“…Sorbitol has been used to induce osmotic stress in sorghum [19], sweet potato (Ipomoea batatas) [20], and tobacco (Nicotiana tabacum L.) [21] cell cultures. PEG has also been used on cell cultures of Stevia rebaudiana [22], sugarcane (Saccharum officinarum L.) [23], scots pine (Pinus sylvestris L.) [24], and Arabidopsis thaliana [25,26].…”

Thermospermine Synthase (ACL5) and Diamine Oxidase (DAO) Expression Is Needed for Zygotic Embryogenesis and Vascular Development in Scots Pine

“…Our results suggest that the adaptability of PA homeostasis may be restricted in Scots pine and, thus, the manipulation of PA levels may not provide as practical tools for the enhancement of stress tolerance as in many flowering plants (Hussain et al, 2011;Marco et al, 2016). In both Scots pine seedlings and proembryogenic cells the expression of the PA biosynthetic and catabolic genes was down regulated rather than up regulated during drought/ osmotic stress, whereas PA contents remained quite stable (Muilu-Mäkelä et al, 2015a;Muilu-Mäkelä et al, 2015b). Therefore, we suggest that PAs may have more potential for biotechnological applications in development related processes such as somatic embryogenesis and the control of wood formation in Scots pine.…”

“…For both clones one representative graft was selected and used repeatedly for cone collection in different years of the PA research (e.g. Vuosku et al, 2006;Vuosku et al, 2012;Muilu-Mäkelä et al, 2015a;Salo et al, 2016). For the present study, cones were collected four times during the growing season of 2004, on July 5 (sampling date I), July 12 (sampling date II), July 19 (sampling date III), and July 26 (sampling date IV).…”