# Request for An Integrated Confocal-Atomic Force Microscopy System

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA RIVERSIDE · 2020 · $190,000

## Abstract

RESEARCH STRATEGY
A. Abstract
The goal of this project is to elucidate the mechanisms for feedback regulation of the tip growth-
signaling machinery by mechanical stresses resulting from rapid and invasive growth of tip-growing
cells and the roles of mechanical feedback regulation in enabling these cells to invade tissues. Fast
tip growth is vital for cells to explore the environment or reach distant destinations via guided and
invasive growth, e.g., fungal pathogens invade host tissue and pollen tubes (PT) travel through female
tissues to deliver sperms. Fast tip growth requires efficient tip-targeted exocytosis and tightly
regulated relaxation of the apical wall inflated by high internal turgor pressure (>1 mPa). Little is
known about how the tip-growing cells regulate the local relaxation of the apical wall to generate
forces for rapid and invasive growth while maintaining the cell wall integrity (CWI). To address this
fundamental question, the PI established Arabidopsis PT as a model system. The PI discovered a
signaling network that is controlled by the ROP1 Rho-family GTPase, modulates apical exocytosis,
and self-regulates ROP1 via autocrine signaling to promote tip growth. Under the prior R01 grant,
modeling was integrated with experimentation to uncover an exocytosis-coordinated design principle
for the regulation of tip growth. ROP1-dependent exocytosis was shown to orchestrate spatial
regulation of ROP1 and wall mechanics to control tip growth and guidance. A microfluidic device-
based tip-chip assay was developed to study invasive growth. Acute tensile stress resulting from
invasive growth was shown to activate ROP1 via the CUP1 putative mechanosensor specifically
required for maintaining CWI in PT experiencing acute stress. In contrast, CUP1 homolog, ANX, is
vital for in vitro CWI likely by sensing gradual tensile stress in PT grown in vitro. This renewal
resubmission will test the hypothesis that CUP1 and ANX sense acute and gradual tensile stresses
respectively, which feedback regulate ROP1 signaling machinery to balance growth with CWI for
efficient apical and invasive growth. Aim 1 will characterize the mechanosensory functions of CUP1
and ANX by integrating genetic and biochemical studies with single molecule mechanosensing and
tip-chip assays. Aim 2 will investigate how mechanosensation by CUP1 cooperates with its sensing
of a RALF peptide to achieve an acute CWI response during invasive growth. Aim 3, by using
iterative modeling and experimentation, will investigate how ROP1 signaling dynamically balances the
wall relaxation with maintenance of CWI, and how this balance allows the tip-growing cells to invade
tissues. The project will advance the concept that the exocytosis-coordinated Rho signaling
overarches fast tip growth, guidance and invasive growth, and will provide unprecedented insights into
the mechanisms behind invasive growth, a process essential for cancer progression and host invasion
by fungal pathogens. With cons...

## Key facts

- **NIH application ID:** 10135744
- **Project number:** 3R01GM100130-06S1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA RIVERSIDE
- **Principal Investigator:** Yongtao Cui
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $190,000
- **Award type:** 3
- **Project period:** 2012-02-01 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10135744

## Citation

> US National Institutes of Health, RePORTER application 10135744, Request for An Integrated Confocal-Atomic Force Microscopy System (3R01GM100130-06S1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10135744. Licensed CC0.

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