{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T10:36:28Z","timestamp":1787567788788,"version":"build-2736575974"},"reference-count":39,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2026,8,23]],"date-time":"2026-08-23T00:00:00Z","timestamp":1787443200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Plants"],"abstract":"<jats:p>Trehalose-6-phosphate (T6P) is a key signalling metabolite that integrates carbon availability with development and stress responses in plants. T6P levels are controlled by trehalose phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) enzymes; however, while TPS enzymes have been studied extensively, the physiological functions of individual TPPs remain incompletely understood. Here, we investigated the role of TPPI in Arabidopsis using loss-of-function tppi mutants, a complemented line (tppi+35S::TPPI), and TPPI-overexpressing (TPPI-OEX) plants. The tppi mutant exhibited delayed flowering accompanied by reduced expression of CO, FT, and SPL3, while complementation restored wild-type (WT) flowering time. TPPI-OEX plants displayed an intermediate flowering phenotype with moderate reductions in CO and FT expression. Under nitrogen starvation, tppi plants showed enhanced anthocyanin accumulation, altered nitrate reductase regulation, characterised by lower total enzyme activity but a higher activation state, and enhanced expression of nitrate assimilation and uptake genes (NIA1, NIA2, NRT1.1, and NRT2.1). TPPI deficiency also altered photosynthetic performance, with enhanced photosystem I (PSI) acceptor-side limitation, increased non-photochemical quenching (NPQ), and a tendency toward reduced photosystem II (PSII) electron transport, indicating altered photosynthetic electron transport and energy dissipation. Taken together, these results indicate that TPPI contributes to the regulation of flowering time, nitrogen responses, and photosynthetic performance, suggesting broader effects of TPPI on plant developmental and physiological processes.<\/jats:p>","DOI":"10.3390\/plants15172559","type":"journal-article","created":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T09:20:02Z","timestamp":1787563202000},"page":"2559","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Trehalose-6-Phosphate Phosphatase I (TPPI) Regulates Floral Transition, Nitrogen Responses, and Photosynthetic Performance in Arabidopsis"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7555-070X","authenticated-orcid":false,"given":"Behzad","family":"Heidari","sequence":"first","affiliation":[{"name":"IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036 Stavanger, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dugassa","family":"Nemie-Feyissa","sequence":"additional","affiliation":[{"name":"IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036 Stavanger, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1349-0363","authenticated-orcid":false,"given":"Amr","family":"R. A. Kataya","sequence":"additional","affiliation":[{"name":"Department of Agroecology, Faculty of Technical Sciences, Aarhus University, 4200 Slagelse, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4430-0382","authenticated-orcid":false,"given":"Peter","family":"Ruoff","sequence":"additional","affiliation":[{"name":"IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036 Stavanger, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cathrine","family":"Lillo","sequence":"additional","affiliation":[{"name":"IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036 Stavanger, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lutz","family":"Andreas Eichacker","sequence":"additional","affiliation":[{"name":"IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036 Stavanger, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"969","DOI":"10.1104\/pp.104.039743","article-title":"Arabidopsis Trehalose-6-Phosphate Synthase 1 Is Essential for Normal Vegetative Growth and Transition to Flowering","volume":"135","author":"Schluepmann","year":"2004","journal-title":"Plant Physiol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"406","DOI":"10.1093\/mp\/ssp114","article-title":"A Single Active Trehalose-6-P Synthase (TPS) and a Family of Putative Regulatory TPS-like Proteins in Arabidopsis","volume":"3","author":"Vandesteene","year":"2010","journal-title":"Mol. 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