Recently, a team led by Hu Peisong, a researcher at the Chinese Academy of Agricultural Sciences and a member of the Chinese Academy of Engineering, published a paper online in the Journal of Integrative Plant Biology. The study identified a major-effect QTL on chromosome 1 of rice that simultaneously controls embryo axis elongation and seedling emergence rate in direct-seeded rice.
Direct-seeding rice, as a novel and simplified cultivation method, shows great potential for development. However, challenges such as high seed rates, low emergence rates, and uneven emergence hinder its wider adoption.
The elongation of the embryo axis and coleoptile in seedlings is the driving force behind seedling emergence in rice. The elongation of the embryo axis is a key factor determining the suitability of rice varieties for direct-seeding. Interestingly, the ancient trait of long embryo axis has been lost in modern cultivated rice, but the genetic basis behind this domestication process remains unclear.
Through positional cloning and genetic complementation experiments, the study confirmed that the "Green Revolution" gene SD1 is the target gene for qME1. It was also discovered that mechanical pressure during rice covering induces the release of ethylene, and the ethylene signaling transcription factor OsEIL1 directly binds to the ME1 gene promoter, promoting GA synthesis. This, in turn, weakens the inhibition of PIF transcription factors by DELLA proteins, ultimately promoting embryo axis elongation in rice.
Domestication studies revealed that the trait of embryo axis elongation has gradually been lost in dwarf breeding, suggesting that the long embryo axis is one of the key factors for wild rice and pre-Green Revolution rice varieties to adapt to harsh conditions during seedling emergence.
Furthermore, the study found that qME1 has advantages such as flood tolerance and early maturity. Ectopic expression of ME1 in the embryo axis region can promote embryo axis elongation without significantly affecting plant height and lodging resistance in rice. In conclusion, this study reveals a new mechanism for regulating embryo axis elongation and seedling emergence in rice, providing valuable insights for breeding new rice varieties suitable for direct-seeding.
Lü Yusong, Associate Researcher at the Chinese Academy of Agricultural Sciences, and Dong Xinli, a Ph.D. student at Zhejiang University, are the co-first authors of the paper, with Hu Peisong, researcher at the Chinese Academy of Agricultural Sciences, Wei Xiangjin, and Tang Shaoqing as co-corresponding authors. The research was supported by the National Natural Science Foundation of China, the Zhejiang Provincial Science and Technology Plan, the Zhejiang Provincial Key Research and Development Program, and the Chinese Academy of Agricultural Sciences Innovation Project.
For more information on the paper, visit: https://doi.org/10.1111/jipb.13671
