Redundant and non-redundant roles of the trehalose-6-phosphate phosphatases in leaf growth, root hair specification and energy-responses in Arabidopsis

The Arabidopsis trehalose-6-phosphate phosphatase (TPP) gene family arose mainly from whole genome duplication events and consists of 10 genes (TPPA-J). All the members encode active TPP enzymes, possibly regulating the levels of trehalose-6-phosphate, an established signaling metabolite in plants. GUS activity studies revealed tissue-, cell- and stage-specific expression patterns for the different members of the TPP gene family. Here we list additional examples of the remarkable features of the TPP gene family. TPPA-J expression levels seem, in most of the cases, differently regulated in response to light, darkness and externally supplied sucrose. Disruption of the TPPB gene leads to Arabidopsis plants with larger leaves, which is the result of an increased cell number in the leaves. Arabidopsis TPPA and TPPG are preferentially expressed in atrichoblast cells. TPPA and TPPG might fulfill redundant roles during the differentiation process of root epidermal cells, since the tppa tppg double mutant displays a hairy root phenotype, while the respective single knockouts have a distribution of trichoblast and atrichoblast cells similar to the wild type. These new data portray redundant and non-redundant functions of the TPP proteins in regulatory pathways of Arabidopsis.