Genetics of In vivo Maternal Haploid Induction

Background

Some plants can produce seeds without fertilization through a process called maternal haploid induction. These seeds carry only the mother’s DNA, which is a powerful shortcut in plant breeding — helping to create uniform, pure lines much faster than traditional methods.

This phenomenon has been most widely studied inmaize, where the genes MTL/NLD/ZmPLA1 have been identified as key to triggering haploid formation. More recently, DMP (DOMAIN OF UNKNOWN FUNCTION 679 membrane protein) genes have been found to play a similar role in other crops like tomato, rice, and Arabidopsis. These genes are often involved in processes related to fertilization, particularly in the behavior or function of thesperm cells.

In maternal haploid induction, something goes wrong (or is purposely disrupted) during fertilization — the male genome either fails to fuse properly with the egg cell or is eliminated shortly after fertilization, allowing the egg to develop on its own.

Although a few inducer genes are known, the detailed mechanisms — such as how these genes affect gamete interaction or why the male genome is lost — are still unclear. Understanding these pathways can open up powerful tools for breeding programsacross a range of crop species.

Aim of the Project

Maternal haploid induction is a rare and powerful process in which seeds are formed without fertilization, resulting in plants that carry only the maternal genome. This phenomenon offers a fast-track method for producing homozygous lines, which is invaluable for modern plant breeding.

The main goal of this project is twofold:

1.To identify novel haploid inducer lines by screening large-scale mutant populations.

2.To generate targeted CRISPR-Cas9 mutants of candidate genes and test whether loss of function enhances haploid induction rates.
In addition to identifying inducers, a major focus is to understand the underlying biological mechanism. Haploid induction is believed to result from defects in the male gamete, such as failed genome delivery or selective elimination of the paternal DNA after fertilization. Genes like MTL, DMP, and related sperm-expressed factors are thought to play key roles in this process, but the precise molecular events remain unclear.

We will use genetic crosses with marker lines to detect haploid offspring and validate inducer lines through molecular markers and ploidy analysis. Promising mutants will undergo detailed spatiotemporal expression profiling and be observed using confocal and live-cell imaging to track cellular events during fertilization and early embryo development.

By combining mutant screening, CRISPR gene editing, and mechanistic analysis, this project aims not only to uncover new maternal haploid inducers, but also to reveal how this fascinating process works — ultimately enabling its use in crop plants for faster, more precise breeding.