A Study of the Spatial Distribution of Gossypol and Other Terpenoids in Cotton Leaves and Ovules

Importance of the Topic

Understanding spatial distribution of terpenoids such as gossypol in cotton tissues is vital for insights into plant defense mechanisms, metabolite synthesis pathways, and crop improvement strategies.

Objectives and Study Overview

This study employed high-resolution imaging mass spectrometry using the iMScope QT to map endogenous terpenoids—gossypol, hemigossypol, and hemigossypolone—in cotton leaves and ovules at the glandular level.

Methodology and Instrumentation

Cotton leaves and ovules were embedded in gelatin, frozen, and cryosectioned to 10 µm thickness. Sections were placed on ITO-coated slides and coated with α-cyano-4-hydroxycinnamic acid matrix (0.7 µm) via sublimation, followed by methanol vapor recrystallization. Mass spectrometry imaging was performed in negative ion mode with 5 µm pixel pitch, 45% laser intensity, 700 shots per pixel, and scan range m/z 150–650. Instruments:

• iMScope QT (AP-MALDI source with Q-TOF analyzer)
• Leica CM1950 cryomicrotome
• iMLayer matrix sublimation system

Main Results and Discussion

Imaging data show that gossypol and hemigossypol concentrations are markedly higher in ovule glands compared to leaf glands, whereas hemigossypolone predominates in leaf glands. Ovule glands exhibit uniform analyte distribution, while leaf gland distribution is heterogeneous and localized to crescent-shaped regions. Signal intensity correlates with gland size and morphology.

Practical Benefits and Applications

This in situ approach delivers high-definition metabolic maps, enabling direct observation of metabolite localization. It supports research on biosynthetic pathways, plant defense, and quality control of bioactive compounds in agriculture and biotechnology.

Future Trends and Potential Applications

Future developments may include integration of imaging MS with genomics and transcriptomics for multi-omic analyses, further enhancement of spatial resolution below 5 µm, and application to a broader range of plant species and metabolites for drug discovery and crop improvement.

Conclusion

iMScope QT proves a robust tool for simultaneous morphological imaging and mass spectrometry, providing detailed gland-level insights into plant terpenoid distribution and laying groundwork for advanced metabolomic research.

Reference

• Dun Junling et al. Mol Plant. 2023;16(12):1990–2003.