Osmotic stress induces genes, enzymes and accumulation of galactinol, raffinose and stachyose in seedlings of pea (Pisum sativum L.)

Wioletta E Pluskota,Joanna Szablińska,Lesław B Lahuta,Ralph L Obendorf,Ryszard J Górecki

doi:10.1007/s11738-015-1905-9

Wioletta E Pluskota, Joanna Szablińska + Show 3 more

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https://doi.org/10.1007/s11738-015-1905-9

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Abstract

The objective of the present study was to recognize the molecular background of the accumulation of raffinose family oligosaccharides (RFOs) in pea (Pisum sativum L.) seedlings under osmotic stress conditions. The exposure of 5-day-old pea seedlings to osmotic stress for 48 h created by immersing roots in PEG8000 solution (−1.5 MPa) induced synthesis of galactinol and RFOs (raffinose and stachyose) in the epicotyl and root tissues, but not in cotyledons. After 24 h of recovery, galactinol completely disappeared, raffinose decreased fourfold and stachyose decreased twofold in roots, but increased in epicotyls. The temporary accumulation of RFOs resulted from a dramatic increase in the enzymatic activity and changes in expression of galactinol synthase (PsGolS), raffinose synthase (PsRS) and stachyose synthase (PsSTS) genes. PsGolS was induced by osmotic stress in both epicotyls as well as in roots. PsRS and PsSTS were induced only in epicotyls, but repressed or remained unaffected in roots, respectively. During recovery, the expression and activity of PsGolS, PsRS and PsSTS dramatically decreased. The expression of PsGolS gene, that level of mRNA transcript significantly decreased during recovery and whose promoter region was identified to contain some stress-related regulating elements, seems to play a crucial role in the biosynthesis of RFOs under osmotic stress. Possible signals that may trigger the induction of expression of PsGolS, PsRS and PsSTS genes and accumulation of RFOs in pea seedlings are discussed.

Highlights

We have found that osmotic stress induces the activity of galactinol synthase (GolS, EC 2.4.1.123) and raffinose synthase (RS, EC 2.4.1.82) in both epicotyl and root tissues of 7-day-old seedlings of winter vetch, but not in cotyledons (Lahuta and Gorecki 2011)
Five-day-old seedlings, in which raffinose family oligosaccharides were completely degraded in tissues of both the epicotyl and root, were used in the osmotic stress experiment
Based on the results of raffinose family oligosaccharides (RFOs) degradation, 5-day-old pea seedlings were chosen for the osmotic stress experiment

Summary

Introduction

Electronic supplementary material The online version of this article (doi:10.1007/s11738-015-1905-9) contains supplementary material, which is available to authorized users. Plant yields can be substantially reduced by adverse environmental events, for example drought, salinity and low and high temperatures. The ability of plants to survive environmental stresses arises from the evolution of various protective mechanisms, including stress-responsive gene expression, modulation of gene expression by the plant hormone abscisic acid (Qin et al 2011), synthesis of stressassociated proteins (Komatsu and Hossain 2013) and the accumulation of certain osmoprotectants or compatible solutes (Yancey 2005). Osmoprotectants, which are neutral and non-toxic, small, organic metabolites, help to maintain water homeostasis in cells during an early response to

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