COMPARTMENTATION OF TREHALOSE 6-PHOSPHATE METABOLISM IN Setaria viridis

TOMAS TONETTI; BRUNO E ROJAS; LUCERO, LEANDRO E.; PAULA CALACE ; PAULA CALACE, TOMAS TONETTI, EZEQUIEL MARGARIT, CARLOS M. FIGUEROA, CARLOS LOBERTTI, CARLOS S. ANDREO, MARIEL C. GERRARD WHEELER, MARIANA SAIGO; FEIL, REGINA; ARRIVAULT, STEPHANIE; STITT, MARK; LUNN, JOHN E.; FIGUEROA, CARLOS M.

Congreso; LVI Reunión Anual de la SAIB; 2020

Trehalose 6-phosphate (Tre6P) is a signal metabolite that coordinates carbon metabolism with plant growth and development. The Tre6P-sucrose nexus model postulates that Tre6P is a signal and a negative feedback regulator of sucrose levels, maintaining intracellular sucrose concentrations within an optimal range. Our current understanding of Tre6P metabolism and signaling in plants is based almost entirely on studies of Arabidopsis thaliana, a C3 eudicot species. In this work, we analysed the intercellular distribution of Tre6P metabolism in leaves from Setaria viridis, a model species for the major C4 crops (such as maize, sorghum and sugarcane). 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 employed established protocols to prepare samples enriched in mesophyll (MC, leaf rolling) and bundle sheath cells (BSC, blending and filtering). Analysis of these samples showed that the SvTPSI.1 transcript and the SvTPSI.1 protein are mainly located in BSC. Using a different separation method (successive sieving of finely ground leaf material suspended in liquid nitrogen through nylon meshes of different pore sizes), 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 data reported for A. thaliana. Our results strongly suggest that Tre6P metabolism occurs in BSC. The knowledge acquired from study of S. viridis will be useful to better understand photoassimilate partitioning and source-sink relations in the major C4 crop species.