The role of the carboxypeptidase AMP1 in cell fate maintenance

• Applicant: Dr. Tobias Sieberer
• Subject Area: Plant Cell and Developmental Biology
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 445008280

As sessile organisms plants adapt their habitus to the specific conditions of their environment. This plasticity in body shape and size is partly achieved through the ability to constantly form new modular organs by the sustained activity of pluripotent stem cells. Under certain conditions pluripotency can be reestablished in cells, which already entered a differentiation program. In specific developmental contexts, this reversion in cell fate appears to be actively suppressed by the existing stem cell niche by a lateral inhibition mechanism and provides a regenerative backup system in case the original stem cell population is lost. Mutation of the putative carboxypeptidase AMP1 in Arabidopsis causes unique hypertrophic phenotypes during embryogenesis as well as in the shoot apical meristem, which can be interpreted as a defect in this lateral inhibition of pluripotency. A role of AMP1 in the miRNA-dependent control of translation has recently been established, however, how this activity is connected to its observed developmental functions is not resolved. Our preliminary work revealed evidence that amp1-related phenotypes are triggered by ectopic activation of HD-ZIP III proteins, a class of miRNA-controlled transcription factors, which mediate stem cell identity during embryo and shoot meristem patterning. The proposed work aims to uncover, to which extend AMP1 suppresses pluripotency in the embryonic suspensor by limiting HD-ZIP III accumulation in this tissue in a miRNA-dependent manner. We would further like to assess the relationship between the AMP1-HD-ZIP III module and the reported auxin-mediated maintenance of suspensor identity. Finally, we also identified three second site modulator mutants of amp1 and we propose the characterization of the corresponding factors, to define novel components in the AMP1 regulatory pathway. The combined results will not only contribute to a better mechanistic understanding of plant stem cell biology but will also provide molecular targets for synthetic biology approaches, to improve urgently needed precision breeding technologies, in which poor regeneration frequently represents the major bottleneck.

• DFG Programme: Research Grants