Characterization of Trehalose-6-Phosphate Synthase and Trehalose-6-Phosphate Phosphatase Genes of Tomato (Solanum lycopersicum L.) and Analysis of Their Differential Expression in Response to Temperature

Abstract

In plants, the trehalose biosynthetic pathway plays key roles in the regulation of carbon allocation and stress adaptation. Engineering of the pathway holds great promise to increase the stress resilience of crop plants. The synthesis of trehalose proceeds by a two-step pathway in which a trehalose-phosphate synthase (TPS) uses UDP-glucose and glucose-6-phosphate to produce trehalose-6 phosphate (T6P) that is subsequently dephosphorylated by trehalose-6 phosphate phosphatase (TPP). While plants usually do not accumulate high amounts of trehalose, their genome encodes large families of putative trehalose biosynthesis genes, with many members lacking obvious enzymatic activity. Thus, the function of putative trehalose biosynthetic proteins in plants is only vaguely understood. To gain a deeper insight into the role of trehalose biosynthetic proteins in crops, we assessed the enzymatic activity of the TPS/TPP family from tomato (Solanum lycopersicum L.) and investigated their expression pattern in different tissues as well as in response to temperature shifts. From the 10 TPS isoforms tested, only the 2 proteins belonging to class I showed enzymatic activity, while all 5 TPP isoforms investigated were catalytically active. Most of the TPS/TPP family members showed the highest expression in mature leaves, and promoter–reporter gene studies suggest that the two class I TPS genes have largely overlapping expression patterns within the vasculature, with only subtle differences in expression in fruits and flowers. The majority of tomato TPS/TPP genes were induced by heat stress, and individual family members also responded to cold. This suggests that trehalose biosynthetic pathway genes could play an important role during temperature stress adaptation. In summary, our study represents a further step toward the exploitation of the TPS and TPP gene families for the improvement of tomato stress resistance.

The trehalose 6‐phosphate phosphatase family in plants

“…Contrastingly, at elevated ambient temperatures, Hwang et al (2019) proposed that the Tre6P signalling pathway determines temperature‐dependent hypocotyl growth in Arabidopsis by inhibiting SnRK1 activity and then allowing the transcription factor PIF4 to promote hypocotyl growth. Other TPPs have also been reported to be induced at elevated temperatures, as observed in tomato (Mollavali & Börnke, 2022). Although the mechanism by which TPPs play a role in temperature stress is not fully understood, it is likely that acquired thermotolerance involves a combination of Tre6P‐dependent signalling, the induction of stress‐responsive genes, the antioxidant defence system and, possibly, a direct role for trehalose as an osmolyte.…”

“…Subsequently, Vandesteene et al (2012) demonstrated that all ten AtTPP proteins (AtTPPA‐AtTPPJ) are catalytically active, as shown by their ability to complement the yeast tps2∆ mutant. Catalytically active TPP enzymes have also been demonstrated in: rice, OsTPP1 (Pramanik & Imai, 2005) and OsTPP2 (Shima et al, 2007); maize, ZmTPP10 (RAMOSA3) (Satoh‐Nagasawa et al, 2006) and ZmTPP4 (Claeys et al, 2019); tobacco ( Nicotiana tabacum ), NtTPPL (Wang et al, 2005); grapevine, VvTPPA (Fernandez et al, 2012); and all five TPP isoforms tested in tomato (Mollavali & Börnke, 2022). Given the widespread conservation of active site residues (Figure 2 and Supplemental Figure S1), it is likely that most, if not all, plant TPPs are catalytically active (Lunn, 2007).…”

“…The study of promoter‐GUS‐GFP lines in Arabidopsis (Van Houtte et al, 2013a; Vandesteene et al, 2012), as well as gene expression profiles (Du et al, 2022; Fernandez et al, 2012; Gao et al, 2021; Hruz et al, 2008; Li et al, 2008; Mollavali & Börnke, 2022; Satoh‐Nagasawa et al, 2006; Waese et al, 2017), have shown that different species have cell‐, tissue‐ and stage‐specific TPP expression patterns (Figures 3B‐C and Supplemental Figure S2). Martínez‐Barajas et al (2011) reported that Tre6P is present at different levels, in a tissue‐ and stage‐specific manner, in wheat grains.…”

“…There is correlative evidence linking trehalose metabolism to temperature stress and the induction of temperature tolerance mechanisms. Under cold stress, activities of TPP genes such as rice OsTPP1 and OsTPP2 (Pramanik & Imai, 2005; Shima et al, 2007), grapevine VvTPPA (Fernandez et al, 2012), tobacco NtTPPL (Wang et al, 2005), tomato SlTPP1 (Mollavali & Börnke, 2022), seven wheat TaTPPs (Du et al, 2022), and Arabidopsis AtTPPD , AtTPPE , AtTPPF , AtTPPG , and AtTPPI (Toufighi et al, 2005; Lin et al, 2023) (Figure 7) are induced as a result of higher sucrose levels. OsTPP1 overexpression in rice also leads to cold tolerance, possibly due to transcriptional reprogramming initiated by the protein and involves the expression of stress‐inducible genes (Ge et al, 2008).…”