Defense-Related Transcriptional Reprogramming in Vitamin E-Deficient Arabidopsis Mutants Exposed to Contrasting Phosphate Availability.

Annapurna D. Allu,Sergi Munné-Bosch,Salma Balazadeh,Bárbara Simancas

doi:10.3389/fpls.2017.01396

Abstract

Vitamin E inhibits the propagation of lipid peroxidation and helps protecting photosystem II from photoinhibition, but little is known about its possible role in plant response to Pi availability. Here, we aimed at examining the effect of vitamin E deficiency in Arabidopsis thaliana vte mutants on phytohormone contents and the expression of transcription factors in plants exposed to contrasting Pi availability. Plants were subjected to two doses of Pi, either unprimed (controls) or previously exposed to low Pi (primed). In the wild type, α-tocopherol contents increased significantly in response to repeated periods of low Pi, which was paralleled by increased growth, indicative of a priming effect. This growth-stimulating effect was, however, abolished in vte mutants. Hormonal profiling revealed significant effects of Pi availability, priming and genotype on the contents of jasmonates and salicylates; remarkably, vte mutants showed enhanced accumulation of both hormones under low Pi. Furthermore, expression profiling of 1,880 transcription factors by qRT-PCR revealed a pronounced effect of priming on the transcript levels of 45 transcription factors mainly associated with growth and stress in wild-type plants in response to low Pi availability; while distinct differences in the transcriptional response were detected in vte mutants. We conclude that α-tocopherol plays a major role in the response of plants to Pi availability not only by protecting plants from photo-oxidative stress, but also by exerting a control over growth- and defense-related transcriptional reprogramming and hormonal modulation.

Highlights

Tocopherol cyclase (VTE1), which is located in plastoglobules (Vidi et al, 2006), is a key enzyme for the biosynthesis of both plastochromanol-8 and vitamin E compounds (Sattler et al, 2003; Szymanska and Kruk, 2010)
A previous study has shown that vitamin E and inorganic phosphate (Pi) availability exert a complex interplay in the control of longevity in Arabidopsis thaliana (Simancas and Munné-Bosch, 2015), nothing is known about the possible influence of vitamin E on plant response to contrasting Pi availability
Wildtype plants were the ones better adapted to low Pi in terms of biomass accumulation, so that priming had positive effects on plant growth. α-Tocopherol deficiency prevented the mutants to benefit from low Pi availability, as indicated by the smaller rosette biomass in both vte mutants compared to wild-type plants under primed conditions at low Pi (Figure 3)

Summary

Introduction

Tocopherol cyclase (VTE1), which is located in plastoglobules (Vidi et al, 2006), is a key enzyme for the biosynthesis of both plastochromanol-8 and vitamin E compounds (Sattler et al, 2003; Szymanska and Kruk, 2010). As the content of plastoglobules is in equilibrium with thylakoid membranes (Austin et al, 2006), both plastochromanol-8 and vitamin E compounds are found in Transcriptional Reprogramming in Vitamin E-Deficient Mutants thylakoids These together fulfill an antioxidant function protecting lipids from the propagation of lipid peroxidation and prevent photosystem II damage, the latter function being performed together with carotenoids (Munné-Bosch and Alegre, 2002; Havaux et al, 2005; Falk and Munné-Bosch, 2010; Zbierzak et al, 2010; Kruk et al, 2014). The gibberellin-DELLA signaling pathway plays a role in the regulation of plant stature, root architecture changes, and anthocyanin accumulation under low Pi-conditions involving ubiquitin-mediated protein degradation (Jiang et al, 2007)

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