The tps5, tps10 and tps11 class II trehalose phosphate synthase mutants alter carbon allocation to starch and organic and amino acids at two different photoperiods in Arabidopsis.

Altered C and N allocation in response to short- and long photoperiods in class II TPS mutants suggest that they negatively regulate the TPS1-Tre6P metabolic regulator system in A. thaliana. The biological function of class II TPS genes remains largely enigmatic, although there is evidence that they may play an important regulatory role in plant stress responses as well as in development and growth. Recent findings indicated that part of biological function of TPSII proteins may be related to their capacity to associate with the SnRK1 regulator of metabolism in order to inhibit its nuclear activity. The results of the present study show that insertional mutants of the TPS5, TPS10 and TPS11 class II TPS genes had a marked effect on the carbon allocation to non-structural carbohydrates, notably starch, and to organic and amino acids during both short- and long-day photoperiods. The results obtained in this study, which resembled those obtained previously in AhTPS1 overexpressing plants, suggest that these particular TPSII proteins may negatively regulate of C and N allocation to non-structural carbohydrates, organic and amino acids mediated by the TPS1-Tre6P central metabolic regulator system in A. thaliana plants. The effect observed was sometimes dependent on of the photoperiod employed and the mutant examined. The mechanism by means of which these TPS II proteins may specifically target TPSI activity and Tre6P levels in order to regulate C and N allocation in A. thaliana in response to short- and long-day photoperiods remains to be determined.