AtTPS1-mediated trehalose 6-phosphate synthesis is essential for embryogenic and vegetative growth and responsiveness to ABA in germinating seeds and stomatal guard cells

Abstract

SUMMARYTrehalose and associated metabolites are part of the sugar signalling system in plants and have profound effects on development. Disruption of the TREHALOSE 6-PHOSPHATE SYNTHASE (TPS1) gene in Arabidopsis results in delayed embryo growth, altered cell wall morphology and carbon metabolism and abortion at the torpedo stage. Here we investigate the role of the TPS1 gene in post-embryonic development using two approaches. In the first we use the seed-specific ABI3 promoter to drive the TPS1 cDNA during embryo development, resulting in rescue of the embryo-lethal tps1 phenotype. Lack of expression from the ABI3::TPS1 transgene in post-germinative tps1 seedlings results in severe growth arrest, accumulation of soluble sugars and starch and leads to an increase in expression of genes related to ABA signalling. In the second approach we use TILLING (targeted induced local lesions in genomes) to generate three weaker, non-embryo-lethal, alleles (tps1-11, tps1-12 and tps1-13) and use these to demonstrate that the TPS1 protein plays a key role in modulating trehalose 6-phosphate (T6P) levels in vegetative tissues of Arabidopsis. All three weaker alleles give a consistent phenotype of slow growth and delayed flowering. Germination of tps1-11, tps1-12 and tps1-13 is hypersensitive to ABA with the degree of hypersensitivity correlating with the decrease in T6P levels in the different alleles. Stomatal pore aperture is regulated by ABA, and this was found to be affected in tps1-12. Our results show that the TPS1 gene product plays an essential role in regulating the growth of vegetative as well as embryogenic tissue in a mechanism involving ABA and sugar metabolism.

The Energy-Signaling Hub SnRK1 Is Important for Sucrose-Induced Hypocotyl Elongation

“…4, B to E). One possible explanation is that KIN10-ox causes a much greater level of SnRK1 activity compared with the tps mutants, which are hypomorphic alleles that harbor reduced Tre6P concentrations (Gómez et al, 2010) and are not completely deficient in Suc-induced hypocotyl elongation (Fig. 1, D and E).…”

“…Phytohormone Signaling and Suc-Induced Hypocotyl Elongation under Light/Dark Cycles: Abscisic Acid ABA suppresses seedling development (Belin et al, 2009) and several studies have linked Tre6P and abscisic acid (ABA) signaling (Avonce et al, 2004;Ramon et al, 2007;Gómez et al, 2010;Debast et al, 2011). Therefore, we investigated whether ABA signaling contributes to Suc-induced hypocotyl elongation under light/dark cycles.…”

“…We used KIN10 overexpression rather than knockouts, because KIN10/11 double knockouts disrupt pollen production and are lethal (Zhang et al, 2001;BaenaGonzález et al, 2007). We also used hypomorphic Targeted Induced Local Lesions In Genomes (TILLING) mutants with reduced TPS1 activity (tps1-11, tps1-12; Gómez et al, 2006Gómez et al, , 2010, which is preferable to tps1 lossof-function mutants that cause seedling developmental arrest (Gómez et al, 2006). First, we investigated the effect of exogenous Suc upon hypocotyl elongation in a variety of photoperiods (Fig.…”

“…For example, tps1 knockout mutants undergo seedling developmental arrest (Gómez et al, 2006), expression of bacterial Tre6P synthase (otsA) or phosphatase (otsB) affects leaf senescence (Wingler et al, 2012), and Tre6P and KIN10 act within a photoperiod-response pathway that controls the induction of flowering (Baena-González et al, 2007;Gómez et al, 2010;Wahl et al, 2013). Signaling by Tre6P and KIN10 is also important for the regulation of growth rates.…”

“…In Arabidopsis (Arabidopsis thaliana), Tre6P is synthesized by trehalose-6-P synthase (TPS). Of 11 TPS homologs encoded by the Arabidopsis genome, TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1) synthesizes Tre6P in plants (Gómez et al, 2010;Vandesteene et al, 2010), and TPS2 and TPS4 are catalytically active in yeast complementation assays (Delorge et al, 2015). Tre6P is believed to regulate SnRK1-mediated signaling by suppressing the activity of SNF1-RELATED PRO-TEIN KINASE1.1 (KIN10/AKIN10/SnRK1.1), which is a catalytic subunit of SnRK1 that is fundamental to the signaling role of SnRK1 (Baena-González et al, 2007;Zhang et al, 2009;Nunes et al, 2013aNunes et al, , 2013b.…”