After being found in mice and nematodes, the selfish genetic element is once again discovered in rice by Chinese scientists. This is the first time that the selfish genetic element is found in plants, challenging the renowned Mendel's Law of segregation. The article introducing such new findings has been published by Science on 8th June 2018. Dr. Xiaowen Yu and Professor Zhigang Zhao are the first authors of this article, who are from the College of Agriculture of Nanjing Agricultural University. Jianmin Wan, an academician of the Chinese Academy of Engineering, is the corresponding author.
What about selfish genes? The core of Mendelian genetics is the concept that gametes are equally likely to carry either of the two parental copies of a gene. In fact, offspring traits might be more similar to those of its father or mother. The same also goes to the selfish genetic element in rice. What's more, such selfish genes weaken the advantages of O. sativa ssp japonica (DJY1) hybrids.
Theoretically, the Indica/japonica hybrids have a 15% yield advantage over the best existing indica/indica hybrids. However, Hybrid sterility, including pollen sterility, aborted embryo sac, low seed-set rate, is always together with hybrid vigor. According to the study by Wan's group, such phenomenon is caused by the selfish genetic elements.
Selfish genetic elements are pervasive in eukaryote genomes, but their role remains controversial. Professor Wan's group from Nanjing Agricultural University discovers the mechanism of hybrid sterility caused by the selfish genetic element. There are two closely related genes ORF2 and ORF3 in hybrid male sterility locus between O. sativa ssp japonica (DJY1) and wild rice (Oryza meridionalis). ORF2 aborts pollen in a sporophytic manner, while ORF3 protects pollen in a gametophytic manner. Moreover, wide compatible varieties created by CRISPR technology to facilitate utilization of the strong hybrid vigor in rice agriculture.
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