Water lilies, both hardy and tropical varieties, are economically and ecologically significant, yet hybridizing them has been a longstanding challenge due to prefertilization barriers. These barriers manifest as poor pollen germination and abnormal pollen tube growth. Abscisic acid (ABA), a plant hormone, is known to regulate pollen viability, but its role in the hybridization barrier has remained unclear. Recent research has pointed to the NpCIPK6–NpSnRK1 module as a key player in this process, influencing ABA synthesis and reactive oxygen species (ROS) accumulation. Based on these challenges, further studies are needed to fully understand how this signaling pathway can be manipulated to enhance hybridization success.
Published (DOI: 10.1093/hr/uhae289) in Horticulture Research on 23 October 2024, a study led by researchers at Nanjing Agricultural University investigates the molecular mechanisms behind hybridization barriers in water lilies. By focusing on the NpCIPK6–NpSnRK1 module, the team uncovered how this signaling pathway affects ABA synthesis and ROS levels in the stigma, ultimately controlling pollen germination. These findings offer new avenues for improving intersubgeneric hybridization in water lilies and other plants facing similar reproductive challenges.
The study reveals that the NpCIPK6 gene is crucial in regulating the hybridization barriers between tropical and hardy water lilies. When activated by intersubgeneric hybridization signals, NpCIPK6 interacts with NpSnRK1 to enhance its kinase activity. This interaction promotes the degradation of NpNCED2, a key enzyme involved in ABA biosynthesis. As a result, ABA levels in the stigma are reduced, impairing the removal of ROS. The accumulation of ROS prevents the germination of incompatible pollen. Interestingly, knockdown of NpCIPK6 or NpSnRK1 increases ABA content in the stigma, facilitating pollen germination on otherwise incompatible stigmas. The study further demonstrates that manipulating this pathway can enhance fruit set in intersubgeneric crosses, offering practical applications in water lily breeding and potentially other crops.
"This discovery sheds light on the complex signaling mechanisms that govern hybridization barriers in water lilies," says Dr. Yingchun Xu, a leading researcher in the study. "Understanding the NpCIPK6–NpSnRK1 pathway not only advances our knowledge of plant reproductive biology but also opens up new possibilities for overcoming hybridization barriers in other plant species. This breakthrough could revolutionize breeding strategies, enabling the development of cultivars with improved traits."
The implications of this research extend beyond water lilies. By targeting the NpCIPK6–NpSnRK1 signaling pathway, scientists may be able to enhance hybridization success in other plants with similar reproductive barriers. This could lead to the development of new cultivars with desirable traits such as enhanced color variation, cold resistance, and improved environmental adaptability. Furthermore, this work contributes to the broader understanding of plant hormonal regulation, offering valuable insights for crop improvement, conservation, and ecological restoration efforts.
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References
DOI
10.1093/hr/uhae289
Original Source URL
https://doi.org/10.1093/hr/uhae289
Funding information
This work was supported by the National Natural Science Foundation of China (grant nos. U1803104 and U2003113), Hainan Natural Science Foundation (grant no. 2021JJLH0031), and Guangxi Natural Science Foundation (grant no. 2022GXNSFBA035635).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.