Analysis of trehalose 6-phosphate metabolism in Setaria viridis leaves

TONETTI, TOMÁS; BRUNO E ROJAS; LUCERO, LEANDRO E.; PAULA CALACE; MARIANA SAIGO; FEIL, REGINA; ARRIVAULT, STEPHANIE; STITT, MARK; LUNN, JOHN E.; FIGUEROA, CARLOS M.

Santa Fe

Congreso; RAFV 2020; 2021

Trehalose 6-phosphate (Tre6P) is a signal metabolite linking plant carbon metabolism with growth and development. The Tre6P-sucrose nexus model postulates that Tre6P is a signal and a negative feedback regulator of sucrose levels to maintain intracellular concentrations within an optimal range. Our current understanding of Tre6P metabolism and signalling in plants is based almost entirely on studies performed with Arabidopsis thaliana, an eudicot performing C3 photosynthesis. In this work, we analysed the intercellular distribution of Tre6P metabolism in leaves of Setaria viridis (Setaria), a model species for the major C4 crops. We found 21 putative transcripts coding for Tre6P-related enzymes: 10 Tre6P synthases (TPS), 10 Tre6P phosphatases (TPP), and 1 trehalase (TRE). Phylogenetic analysis showed there is only one Class I TPS isoform (SvTPSI.1, responsible for Tre6P synthesis) and nine Class II TPS isoforms (putatively involved in Tre6P perception and/or signalling). We prepared samples enriched in mesophyll cells (MC) by leaf rolling, and in bundle sheath cells (BSC) by blending and filtering. Analysis of these samples showed that the SvTPSI.1 transcript and protein are mainly located in BSC. Using a different separation method (suitable for the analysis of metabolites) we found that Tre6P is mainly located in BSC. Finally, incubation of isolated BSC strands with 1 mM Tre6P inhibited degradation of transitory starch, which fits the data reported for A. thaliana. Our results strongly suggest that Tre6P metabolism occurs in BSC and represent an initial step towards the elucidation of Tre6P signaling in C4 photosynthesis.