Functional Characterization of Class I Trehalose Biosynthesis Genes in .

The function of trehalose metabolism in plants during growth and development has been extensively studied, mostly in the eudicot . So far, however, not much is known about trehalose metabolism in the moss . Here, we show that in , two active trehalose-6-phosphate synthase enzymes exist, PpTPS1 and PpTPS2. Expression of both enzymes in can complement the glucose-growth defect of the yeast mutant. Truncation of N-terminal extension in PpTPS1 and PpTPS2 resulted in higher TPS activity and high trehalose levels, upon expression in yeast. knockout plants were generated and analyzed in various conditions to functionally characterize these proteins. and knockouts displayed a lower amount of caulonema filaments and were significantly reduced in size of gametophores as compared to the wild type. These phenotypes were more pronounced in the mutant. Caulonema formation is induced by factors such as high energy and auxins. Only high amounts of supplied energy were able to induce caulonema filaments in the mutant. Furthermore, this mutant was less sensitive to auxins as NAA-induced caulonema development was arrested in the mutant. In contrast, formation of caulonema filaments is repressed by cytokinins. This effect was more severe in the and mutants. Our results demonstrate that PpTPS1 and PpTPS2 are essential for sensing and signaling sugars and plant hormones to monitor the balance between caulonema and chloronema development.