The layered effect: A single-cell map of corn's root reveals a regulator of cellular diversity

The middle layer of cells called the endodermis is where the expression of the SHR gene is found. Multiple layers of cortex have been known to play roles in flooding stress, and SHR communicated with outer layers to generate them. Carlos Ortiz-Ramrez has a credit.

A new study uses novel single-cell profiling techniques to reveal how plants add new cell layers that help them resist climate stressors. Corn is a critically important crop around the world and the research is trying to create a cell-by-cell map of the plant's root system.

The cortex tissue of corn makes up a lot of the crop's root system. Adding layers to the cortex tissue is a key evolutionary feature that can help plants cope with flooding and other weather conditions, according to Kenneth Birnbaum, a professor in New York University's Department of Biology and Center for Genomics and Systems Biology and the senior author of the paper.

The project was led by the lab at NYU and involved researchers from the University of Pennsylvania and Cold Spring Harbor Laboratory.

To create a map of the corn root, the researchers first broke apart the root using cell-wall digesters to create single, free-floating cells. New approaches allowed them to analyze the content of individual cells using single cell-sequencing techniques.

They mapped the cells back to their location in the corn root, like assembling a 10,000-piece jigsaw puzzle without a guide. The researchers used fluorescent dyes that penetrated into root tissues at variable depths to label and isolated different layers, like separating the layers of an onion, to solve the puzzle.

The NYU Center for Genomics and Systems Biology and the UGA Laboratorio Nacional were able to recreate a 3D model of gene expression throughout the corn root by using the second layer of information.

The cortex of the corn root was revealed to be undescribed in the new map. The cortex is important because it contains the bulk of the early corn root. Crop plants cope with environmental stressors by using the cortex cellular subtypes. Increased cooperation could help reduce the carbon footprint of agriculture by exchangingycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizalycorrhizal Middle layers of cortex allow for gas exchange during flooding, while on-demand expansion of the cortex can reduce water loss during a dry spell.

"We mapped out four distinct cortex layer signatures that could provide important genetic targets for further improvement in symbiosis, flooding, and drought," said Ortiz Ramirez.

The group found some clues about how corn could create the extra layers of cortex. Short root (SHR), the key gene regulator that is similar across different plants, was in an intriguing position that was different from other plants with just one layer of cortex.

SHR was one of the first transcription factors shown to move from cell to cell, allowing inner cell types to give instructions to middle layers to create a new tissue. SHR is a type of local organizing, directing root tissues to assemble around a core pattern. In corn, the single-cell map showed that SHR was in a new position next to the multiple layers of cortex, a convenient "jumping off" point to expand the multiple cortex layers. The researchers found that SHR was moving multiple layers through the cortex, and that it was hyper mobile.

The number of cortex layers in corn and foxtail millet was reduced by the disturbed SHR function. SHR's role in expanding tissue layers and generating new cell identities was kept the same, but it switched location to add new cell types that allow corn to cope with environmental stresses.

"Identifying SHR has a key regulator of cortex expansion is an important first step." Changing the number of cortex layers could allow plants to use less fertilization or grow in less-fertilized soil, if the regulators are changed.

The ground tissue circuitry regulates organ complexity in maize and Setaria.

Science journal information.

A single-cell map of corn's root reveals a regulator of cellular diversity.

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