Science and Technology Daily (Reporter Qu Yizhen and Wang Zhuhua)

On April 9, this reporter learned from Hainan University that the latest discovery of Li Jing's team from Sanya Nanfan Research Institute of Hainan University is that ambient temperature may be a key factor to be considered in the creation and optimization of haploid inducers, and that the flexible control of ambient temperature can fully tap the potential of CenH3-based haploid-induced technology, providing key clue to the creation, optimization, and promotion of haploid-induced technologies in a wide range of crops. The results were published in the international journal Nature Plants under the title of "A strategy to optimize the induction efficiency of maternal and paternal haploids by flexible growing ambient temperature control".

Haploid induction is one of the key technologies at the forefront of the seed industry, but there is still a lack of haploid inducers that can be efficiently and conveniently applied in most of the crops, which has become a critical technical bottleneck limiting its wide application.

Previous studies have found that the removal of the inducer genome during early post-fertilization embryonic development of seeds is one of the main mechanisms for the formation of haploid embryos. CENH3 (CENPA) is a centromere-specific histone variant that functions primarily to maintain normal chromosome segregation during cell division.

In studying the mechanism of haploid formation, Li Jing's team found that the pollen viability and haploid-inducing ability of GFP-tailswap, the most classical and efficient haploid inducer in Arabidopsis thaliana, were highly sensitive to ambient temperature compared to wild-type plants. Slightly increasing the ambient temperature to around 22°C to 25°C can not only cause both an almost complete loss of GFP-tailswap pollen viability but also a significant increase in haploid induction, and decreasing the temperature had the exact opposite effect.

The team further found that the sensitivity of the induction ability to the environment is a common characteristic of CENH3-based inducer, and that by increasing the temperature it is possible to directly optimize the induction process of the parental haploid in terms of both simplifying emasculation and increasing the induction efficiency simultaneously.

In fact, for maternal haploid induction using the pollen of the inducer, changing the temperature produces a pair of conflicting effects; increasing the temperature boosts efficiency but severely reduces pollen viability, making induction practically impossible to perform. After careful analysis and validation, the team found that the effect of temperature on induction efficiency occurs mainly after fertilization, i.e., independent to the effect on pollen viability. Based on this finding, the team designed a strategy to induce maternal haploids under high-temperature conditions through the use of low-temperature-responsive pollen. With this strategy, they succeeded in significantly optimizing maternal haploid induction in terms of both pollen supply and induction efficiency.

"We are eager that the discovery in Arabidopsis will once again demonstrate the great value of basic research in model crops." Said Li Jing. The research provided important clues to reveal key basic biological questions such as the precise segregation control of chromosomes and the mechanism of haploid formation during the maintenance of cell division by CENH3, as well as provided highly valuable clues for the extension of CENH3-based haploid inducers to other crops.