Decoupling the chemical and physical origins of the seed spectral manifold in sorghum

Authors: Baek, Insuck; LIM, SEUNGHYUN - Orise Fellow; HWANG, CHANSONG - Non ARS Employee; Kim, Moon; Park, Sunchung; Prom, Louis; MAGILL, CLINT - Texas A&M University; Meinhardt, Lyndel; Ahn, Ezekiel

Submitted to: NPJ Systems Biology and Applications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2026
Publication Date: 5/11/2026
Citation: Baek, I., Lim, S., Hwang, C., Kim, M.S., Park, S., Prom, L.K., Magill, C., Meinhardt, L.W., Ahn, E.J. 2026. Decoupling the chemical and physical origins of the seed spectral manifold in sorghum. NPJ Systems Biology and Applications. https://doi.org/10.1038/s41540-026-00728-w.
DOI: https://doi.org/10.1038/s41540-026-00728-w

Interpretive Summary: Seeds are often described simply by their color, like "red" or "white," but this misses the complex way they interact with light to protect themselves. To see the full picture, we treated the optical properties of sorghum seeds not as a simple color, but as a complex "spectral landscape" using advanced hyperspectral cameras that see beyond the visible range. We discovered that a seed's interaction with light is controlled by two completely independent genetic switches: a "Chemical Palette" that paints the seed with pigments for color, and a "Physical Barrier" that builds the microscopic texture of the seed coat to scatter invisible light. We even identified a specific gene that acts as a structural engineer, reinforcing the seed's physical armor without changing its color, and used computer simulations to predict how we can breed "optically designed" seeds. This research gives plant breeders a new roadmap to design crop "skins" that are custom-built to reflect heat or resist pests, ensuring food security in a changing climate.

Technical Abstract: Biological structures interact with light as high-dimensional manifolds, yet phenotypes are often reduced to scalar metrics; to resolve this, we defined the "Seed Spectral Manifold" in sorghum, integrating hyperspectral imaging, structural equation modeling, and genomics to deconstruct the genetic architecture of light-matter interactions. We demonstrated that the optical phenotype is composed of two nearly orthogonal genetic axes: a "Chemical Palette" governed by pigmentation loci and a "Physical Barrier" constrained by structural biophysics. Path analysis revealed that genetic control of near-infrared (NIR) scattering is largely indirect, mediated through seed mass and projected area, while a specific pleiotropic locus on Chromosome 6 (linked to a DUF6598-domain gene) was identified as a master regulator of the physical axis, jointly modulating NIR reflectance and spectral entropy. By performing in silico genetic perturbations, we successfully predicted coherent deformations of the spectral manifold, establishing a framework for the computational design of seed optics and proving that "structural optics" can be genetically decoupled from pigmentation for targeted breeding.