MLO Signaling in Polarized Plasma Membrane Domains

Humans have harnessed the power of plants to provide the bulk of their calories through seeds which are a direct product of pollination. Plants are rooted in place and are therefore continually assaulted by both biotic and abiotic stressors in nature while also striving to grow and reproduce. As the world population continues to grow in a changing climate, the ability to ensure food security relies on a better understanding of how plant cells make the appropriate response to signals from their environment.

This project uses pollination and tip-growing cells as model systems for dissecting how plant cells perceive signals from other cells and scale their responses to promote beneficial interactions and discourage harmful interactions. This research has the potential to impact society by leading to new approaches for enhancing beneficial plant-biotic interactions in the extreme environments that plants will face if global climate change continues at its current pace.

In addition to training the next generation of scientists through direct participation of undergraduates, graduate students, and a postdoc, this project will also enhance STEM participation and education of underrepresented minorities at the high school level through a summer educational outreach and mentoring program at an inner city community center.

Receptor-like kinases (RLKs) play key roles in perceiving and reacting to external signals secreted from an invading organism or cell wall perturbations that result from attempted invasions. FERONIA (FER) and related RLKs have been proposed to be sensors of extracellular perturbations that trigger a signal transduction cascade that results in communication with the invading cell.

In pollination, one outcome of FER signaling is the signal-mediated trafficking of the MLO protein NORTIA to a polarized membrane domain in the synergid cells of the female gametophyte. FER-mediated trafficking of MLO proteins to discrete polar membrane domains may act as a mechanism to turn up the volume on the extracellular response. However, knowledge is lacking on the extent to which MLO proteins act as amplifiers of FER signaling in other parts of the plant.

The overall objective of this project is to understand the link between RLK signaling and MLO accumulation and function at polarized membrane domains. The central hypothesis is that MLO amplification of FER signals to the extracellular space is a common mechanism in RLK regulation of both plant-biotic interactions at polarized membrane domains and polarized cell expansion and acts to modulate the cellular response to external signals.

The overall objective will be met through three specific aims: 1) testing conservation of the FER/MLO signaling module in plant-biotic interactions and tip-growing cells; 2) determining the intersection of FER and MLO activities in polarized membrane domains; and 3) identifying new proteins involved in MLO function in polarized membrane domains.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.