Overcoming redundancy in the arabidopsis TREHALOSE-6-PHOSPHATE PHOSPHATASE family reveals connections to development and iron homeostasis
Arabidopsis encodes ten TREHALOSE-6-PHOSPHATE PHOSPHATASE (TPP) genes, homologous to maize RAMOSA3, which controls shoot branching in maize. To explore the roles of the arabidopsis TPPs, we analyzed their expression in shoot apices and found distinct spatial patterns, including TPPI and TPPJ expressed in shoot meristem boundaries, reminiscent of RA3 expression. Single and double mutants in these TPP genes lacked obvious phenotypes, however a CRISPR-Cas9 knockout of all ten TPP genes resulted in increased branching, mirroring ra3 mutants in maize, as well as reduced size and earlier flowering. Expression of GFP-tagged TPPI under its native promoter partially complemented these defects, with protein localization in meristems, vascular tissues and in nuclei. Metabolite profiling revealed higher trehalose 6-phosphate (Tre6P), lower trehalose, and altered sugar and iron-associated metabolites. The mutants were also chlorotic, and grew poorly on low-nutrient media, linked to low iron levels, and reversible with iron supplementation. Consistent with these findings, developmental and iron-responsive genes were up-regulated in the 10x tpp mutants, while photosynthesis-related genes were repressed. Our findings suggest that TPP genes redundantly regulate shoot architecture, sugar metabolism, iron homeostasis and photosynthesis in arabidopsis, and support a role for TPP-mediated Tre6P signaling in coordinating developmental and physiological pathways.