Scientists Uncover Vital Role of Maternal Small RNAs in Plant Breeding
Plant breeders, aiming to develop resilient and high-quality crops, often cross plants from different species to transfer desirable traits. However, they frequently encounter a major obstacle: hybrid seed failure. This reproductive barrier often prevents closely related species from producing viable seeds. A new study from the Max Planck Institute of Molecular Plant Physiology offers insights into this challenge by identifying small RNA molecules as crucial players in this process. These findings could pave the way for more successful hybridization in the future.
Viable seeds produced by Capsella orientalis on the left side and collapsed, non-viable seeds produced by crossing Capsella orientalis with its near relative Capsella rubella. A lack of maternal small RNA was found responsible for this discrepancy in seed quality.
© Katarzyna Dziasek
When hybrid seeds fail to develop, the reason often lies in the endosperm-a tissue in plant seeds that provides nutrients to the growing embryo, much like the placenta nourishes mammalian embryos. Without proper development of the endosperm, the seeds cannot survive. A new study led by Prof. Dr. Claudia Köhler's research group has made a key discovery in the Brassicaceae family, which includes mustard, broccoli, rapeseed, and other important crops. The study reveals a strong link between hybrid seed failure and a deficiency in maternal small RNAs. These tiny molecules are transferred from the maternal plant to the endosperm and control gene activity in the endosperm. When the gene expression in a seed is abnormal, seed development halts, ultimately leading to its death.
"Our findings suggest that the dosage of maternally provided small RNAs can determine whether a hybrid seed will grow or not," said Katarzyna Dziasek, the study's lead author. "By controlling the levels of these RNA molecules, we may be able to improve the survival of hybrid seeds and overcome the barriers that have long prevented successful breeding between different plant species."
Interestingly, this mechanism extends beyond plants. A similar phenomenon known as hybrid dysgenesis occurs in fruit flies. In this case, small RNAs from the mother protect against genetic disorders that can occur if the father's genetic material deviates too much. Thus, in both plants and animals, maternal small RNAs play a pivotal role in determining species compatibility in hybridization. Key questions remain about how these small RNAs are generated and transferred from the maternal plant to the endosperm, which are currently under investigation in Claudia Köhler's lab at the Max Planck Institute of Molecular Plant Physiology.
As plant breeders continue to face the challenges of hybrid seed failure, this research provides a promising new avenue for enhancing the transfer of beneficial traits between species. By understanding the molecular mechanisms behind hybrid seed failure, breeders may be able to develop more resilient crops that can better withstand environmental stresses, improve yield, and maintain biodiversity.
