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Chinese scientists have found the “switch” that regulates the germination of rice and wheat ears – Teller Report

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According to news from IT House on December 6, according to CCTV News, Chu Chengcai’s team and Gao Caixia’s team from the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences recentlyFound two “switches” to regulate rice and wheat ear germination, including the key gene SD6 that negatively regulates seed dormancy and the gene ICE2 that positively regulates seed dormancy. The researchers believe that the two genes “double swords”,Promising solution to massive agricultural losses due to germination of seed ears. The results were published online on December 6 in the journal Nature Genetics.

According to the website of the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, seed dormancy refers to the phenomenon that seeds cannot germinate under conditions suitable for their growth (temperature, moisture, oxygen, etc.).It is an adaptive trait shared by most higher plants. In the process of crop domestication, due to more consideration of high-yield, high-quality, resistance to diseases and insect pests, and stress-tolerant traits, while ensuring that the seeds have consistent germination characteristics during production, the retention of moderate dormancy of seeds is often ignored, resulting in many crops such as rice, In the production of wheat, a large area has encountered serious ear germination problems, that is, the phenomenon of seed germination on the ear before harvest in humid weather during the seed maturity period,Caused a huge economic loss at the last moment of the harvest, which was close to failure. Therefore, to find the key genes controlling seed dormancy, such as rice and wheat, to clarify the molecular physiological mechanism of seed dormancy regulation, and to excavate its excellent allelic variation,It is very important to solve the panicle germination disaster of rice and other crops.

▲ Rice panicle germination occurs frequently in many major rice regions across the country | The picture is from the website of the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, the same below

However, seed dormancy is an extremely complex agronomic trait,Regulated by a large number of quantitative trait loci and significantly influenced by multiple environmental factors. As a result, the cloning of key regulatory genes for seed dormancy is difficult, and there is a lack of practical main gene resources for production.In view of this situation, Chu Chengcai’s team from the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences successfully obtained fromA key gene SD6 controlling rice seed dormancy was cloned from a strong dormancy rice variety Kasalath, and confirmed that SD6 negatively regulates rice seed dormancy.By screening SD6 interacting proteins, the research team discovered another rice transcription factor ICE2 positively regulates rice seed dormancy.

Through experiments in molecular biology, genetics and biochemistry, the research team revealed that both SD6 and ICE2 directly target the ABA8ox3 promoter of the abscisic acid (ABA) 8′-hydroxylase gene, and they respectively recognize the G on the promoter. -box motif or E-box motif to achieve reverse regulation of the same target gene. On the other hand, SD6 and ICE2 indirectly regulated the key synthesis regulatory gene of ABA, namely 9-cis-epoxycarotenoid dioxygenase gene NCED2, through antagonistic regulation of another transcription factor OsbHLH048. These findings reveal a new regulation paradigm of hormone balance, that is, antagonistic transcription factor pairs can directly regulate ABA metabolism and indirectly regulate ABA synthesis, thereby achieving timely and efficient regulation of ABA content to switch between seed dormancy and sprout.

Seed dormancy is regulated by both genetics and the environment in which the seeds are exposed. Temperature is the most important environmental factor affecting seed dormancy and germination. A warm environment usually accelerates the release of seed dormancy and promotes seed germination, while low temperature keeps the seeds in a dormant state. Through this ability to sense the external environment, the seeds can survive adverse environmental conditions, such as low temperature in winter.Chu Chengcai’s research team found that The SD6-ICE2 molecular module has the characteristics of sensing the temperature of the surrounding environment and regulating the dormancy of seeds: Under normal temperature conditions, the SD6 gene maintains a high level of expression and exerts its function, while the expression of the ICE2 gene is significantly inhibited, thereby promoting seed germination; under low temperature conditions, the expression of the SD6 gene is significantly inhibited, and the expression of the ICE2 gene is up-regulated. This keeps the seeds in a dormant state. This result indicated that SD6-ICE2 could dynamically control the ABA content in seeds by sensing the change of external environment temperature, thereby adjusting the dormancy intensity of seeds to adapt to natural climate change.This also explains how seed dormancy acts as an adaptive strategy to avoid unfavorable conditions.

▲ SD6 / ICE2 molecular module action model and application examples

A near-isogenic line containing a strong dormant allele of SD6 exhibited excellent ear germination resistance in field,It is suggested that this natural variation site can be used for dormant conventional breeding improvement of high-quality rice main varieties. At the same time, the SD6 gene of several rice varieties that are easy to germinate easily was improved by gene editing technology. The research team confirmed that the panicle germination of the improved materials under the background of different rice varieties encountered continuous rainy weather during the harvest period. significantly improved.Gao Caixia’s team improved the TaSD6 gene of wheat variety Kenong 199, which can also greatly improve the resistance of wheat ear germination, indicating that the function of SD6 gene in controlling seed dormancy in rice and wheat is conserved, that is, SD6 has important application value in rice and wheat ear germination resistance breeding improvement.

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