Unraveling the Molecular Mystery: Researchers Uncover Key to Plants' Response to Changing Conditions

February 6, 2024

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by Daegan Miller, University of Massachusetts Amherst

Researchers from the University of Massachusetts Amherst recently unveiled a landmark study addressing a crucial biological question: How an organism initiates a broad spectrum of cellular processes in response to an internal or external change to thrive during favorable times and endure during adverse times?

The study, focusing on plants and published in the Cell journal, reveals the interactions among four compounds: pectin, the FERONIA and LLG1 receptor proteins, and the RALF signal peptide. The researchers specifically uncovered that a molecular condensation process, known as liquid-liquid phase separation, happening between pectin and RALF at the interface of the cell wall-cell membrane, orchestrate how a stimulus activates various cellular processes. As a result, the plant initiates a beneficial response.

Alice Cheung, Distinguished Professor of Biochemistry and Molecular Biology at UMass Amherst and the article's lead author, explains that 'biologists often operate linearly: we observe a stimulus input and then follow a specific response along a predicted cellular pathway responsible for that reaction. However, cells manage numerous pathways, continually maintained, and synchronized.'

Together with Hen-Ming Wu, her long-serving collaborator and co-lead author of the study, Cheung has long broached the subject of stimulus and response since identifying in 2010 and 2015 that the FERIONIA-LLG1 receptor pair is an ideal model to uncover this complex puzzle. The FERONIA-LLG1 receptor significantly influences all plant life facets—from seedling growth to maturity and reproduction, to persevering through various challenges like diseases and extreme climates.

Cheung points out that 'this study would not have been possible without the collective work of junior colleagues and co-first authors of the paper, postdoc James Ming-Che Liu and graduate student Jessica Fang-Ling Yeh, and a recently graduated molecular and cellular biology Ph.D. student, Robert Yvon.'

The team initiated the study by exploring how the RALF signal (or ligand) affects the FERIONIA-LLG1 receptor in the cell membrane. They observed uncharacteristic results: the cell did not simply internalize FERONIA-LLG1, a process called endocytosis which typically follows, instead, all cell membrane molecules tested were affected. Additionally, the RALF ligand remained outside the cell, within a pectin-rich extracellular matrix or the cell wall, contrasting to a typical ligand-receptor interplay.

The team proceeded to study the biochemical and biophysical interactions among the four molecules, how these interactions influenced their behavior on the cellular level, and their effect on plant physiological responses encountering two frequent environmental stressors—increased temperature and salinity.

The findings offer the first-time insight into the mechanism of how plant cells harmonize various pathways in response to a singular stress signal to boost resilience and ensure survival. The study also demonstrates for the first time how phase separation at the cell wall-cell membrane interface, where a plant cell detects and responds to external stimuli, significantly impacts a collective cellular response.

Cheung asserts that 'it would have been impossible to carry out the work without the facilities provided by the Institute of Applied Life Sciences and the input of James Chambers, director of Light Microscopy Core and co-author on this paper.'

Courtesy of University of Massachusetts Amherst