# Quick creation and mapping of EMS‐induced maize kernel mutants identifies classical gene ZmBT1 and novel gene ZmTOP6A

## TL;DR

This study used chemical mutagenesis to identify two genes, ZmBT1 and ZmTOP6A, that are important for maize kernel development.

## Contribution

The study identifies ZmTOP6A as a novel gene involved in maize kernel development and confirms ZmBT1's role using EMS mutagenesis and BSA.

## Key findings

- A missense mutation in ZmBT1 causes shrunken kernels in maize.
- A start-lost mutation in ZmTOP6A leads to small, non-germinating kernels.
- BSA and genome sequencing effectively mapped these mutations to their respective genes.

## Abstract

Maize (Zea mays L.) kernel mutants are valuable tools for investigating kernel development. In this study, we employed ethyl methanesulfonate (EMS) mutagenesis of pollen on five inbred lines, which displayed varying performance after treatment. Over 400 independent kernel mutants were generated, showing a wide range of defects in both type and severity. Bulked segregant analysis (BSA) combined with whole‐genome sequencing was employed to map two representative mutants. For a shrunken kernel mutant, a missense mutation (P155L) was identified in the classical ZmBT1 gene, which encodes an ADP‐glucose transporter. For a small kernel mutant, a start‐lost mutation (M1?) was discovered in the ZmTOP6A gene, which encodes the DNA topoisomerase VI subunit A. Allelic verification of ZmBT1 and ZmTOP6A confirmed their association with the mutant phenotypes. Furthermore, we analyzed the protein conservation, expression patterns, and subcellular localization of both genes. Our study highlights the effectiveness of combining EMS mutagenesis with BSA for mining maize kernel genes. The mutants and the identified genes will advance our understanding of maize kernel development.

Ethyl methanesulfonate mutagenesis of pollen was performed on five maize inbred lines, resulting in over 400 kernel mutants.ZmBT1 was identified as responsible for a shrunken kernel mutant, while ZmTOP6A was responsible for a small kernel mutant.The protein conservations, expression patterns, and subcellular localizations of ZmBT1 and ZmTOP6A were analyzed.

Ethyl methanesulfonate mutagenesis of pollen was performed on five maize inbred lines, resulting in over 400 kernel mutants.

ZmBT1 was identified as responsible for a shrunken kernel mutant, while ZmTOP6A was responsible for a small kernel mutant.

The protein conservations, expression patterns, and subcellular localizations of ZmBT1 and ZmTOP6A were analyzed.

Maize (corn) is an important crop around the world, used for animal feed, industrial raw materials, human food, and scientific research. Understanding how maize kernels grow is crucial for improving crop yield and making them more resilient. This study used a chemical called ethyl methanesulfonate to cause mutations and paired this with advanced gene‐mapping methods to identify the genes responsible. Over 400 maize kernel mutants were created from five maize inbred lines. Two important genes were discovered: ZmBT1, which controls starch production and causes shrunken kernels when mutated, and ZmTOP6A, a new gene that helps maintain DNA topological structure. Mutations in ZmTOP6A led to small kernels that could not germinate. This study offers a useful approach for finding important genes in maize, and the mutants and genes discovered will help improve our understanding of kernel growth, which could be useful for future maize improvements.