Abstract
Trehalose metabolism and its intermediate trehalose-6-phosphate (T6P) are implicated in sensing and signalling sucrose availability. Four class I TREHALOSE-6-PHOSPHATE SYNTHASE (TPS1) genes were identified in kiwifruit, three of which have both the TPS and trehalose-6-phosphate phosphatase (TPP) domain, while the fourth gene gives rise to a truncated transcript. The transcript with highest sequence homology to Arabidopsis TPS1, designated TPS1.1a was the most highly abundant TPS1 transcript in all examined kiwifruit tissues. An additional exon giving rise to a small N-terminal extension was found for two of the TPS1 transcripts, designated TPS1.2a and TPS1.2b. Homology in sequence and gene structure with TPS1 genes from Solanaceae suggests they belong to a separate, asterid-specific class I TPS subclade. Expression of full-length and potential splice variants of these two kiwifruit TPS1.2 transcripts was sufficient to substitute for the lack of functional TPS1 in the yeast tps1Δ tps2Δ mutant, but only weak complementation was detected in the yeast tps1Δ mutant, and no or very weak complementation was obtained with the TPS1.1a construct. Transgenic Arabidopsis lines expressing kiwifruit TPS1.2 under the control of 35S promoter exhibited growth and morphological defects. We investigated the responses of plants to elevated kiwifruit TPS1 activity at the transcriptional level, using transient expression of TPS1.2a in Nicotiana benthamiana leaves, followed by RNA-seq. Differentially expressed genes were identified as candidates for future functional analyses.
Highlights
Trehalose has a central role as an energy source and in stress response in microorganisms and invertebrates [1]
Four class I TREHALOSE-6-PHOSPHATE SYNTHASE (TPS1) genes were identified in kiwifruit, three of which have both the trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) domain, while the fourth gene gives rise to a truncated transcript
Expression of full-length and potential splice variants of these two kiwifruit TPS1.2 transcripts was sufficient to substitute for the lack of functional TPS1 in the yeast tps1Δ tps2Δ mutant, but only weak complementation was detected in the yeast tps1Δ mutant, and no or very weak complementation was obtained with the TPS1.1a construct
Summary
Trehalose has a central role as an energy source and in stress response in microorganisms and invertebrates [1]. It has an important role as osmotic protectant in bacteria, fungi, archaea and insects [2] and is thought to protect against desiccation in specialized resurrection plant species. In most plant species trehalose is accumulated in trace amounts and is unlikely to be important as an osmoprotectant. Trehalose metabolism is implicated in providing a link between plant metabolism and development [3], with its intermediates sensing and signalling carbon availability [4,5]. PLOS ONE | DOI:10.1371/journal.pone.0168075 December 19, 2016
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