Compartmentalization of trehalose 6-phosphate metabolism in C4 species

FIGUEROA CM

Buenos Aires

Conferencia; Max Planck Latin America Conference on Scientific Collaboration; 2022

Max Planck Society

Trehalose6-phosphate (Tre6P) is a signal metabolite linking plant carbon metabolism withgrowth and development. The Tre6P-sucrose nexus model postulates that Tre6P isa signal and a negative feedback regulator of sucrose levels. Our currentunderstanding of Tre6P metabolism and signalling in plants is based almostentirely on studies performed with Arabidopsisthaliana, an eudicot performing C3 photosynthesis. The aim ofour group is to investigate the occurrence and intercellular distribution of Tre6Pmetabolism in leaves of Setaria viridis,a model species for the major C4 crops. We found 21 putativetranscripts coding for Tre6P-related enzymes: 10 Tre6P synthases (TPS), 10Tre6P phosphatases (TPP), and 1 trehalase (TRE). Phylogenetic analysis showedthere is only one Class I TPS isoform (SvTPSI.1, responsible for Tre6Psynthesis) and nine Class II TPS isoforms (putatively involved in Tre6Pperception and/or signalling). Analysis of samples enriched in mesophyll cells(MC) and bundle sheath cells (BSC) showed that the SvTPSI.1 transcript and its encoded proteinare mainly located in BSC. Using a different separation method(suitable for the analysis of metabolites) we found that Tre6P is mainlylocated in BSC.Finally, incubation of isolated BSC strands with 1 mM Tre6P promoted theaccumulation of SvSWEET13a and SvSWEET13b transcripts. Theseresults strongly suggest that Tre6P metabolism occurs in BSC, where it couldregulate sucrose export to the apoplast by modulating the levels of SWEETtransporters. Overall, our work represents an initial step towards theelucidation of Tre6P signaling in C4 photosynthesis.