Recently, a study conducted by the Agricultural Biotechnology Research Center of the Guangdong Academy of Agricultural Sciences in collaboration with Sun Yat-sen University and the Rice Research Institute of the Guangdong Academy of Agricultural Sciences has uncovered a new mechanism regulating rice yield through the miR397-OsLAC-OsTTL pathway. The findings have been published online in The Plant Cell.
"We have revealed the molecular mechanism by which the miR397-OsLAC-OsTTL pathway mediates brassinosteroid signaling to regulate rice yield," said Yang Yu, the first author of the paper and associate researcher at the Agricultural Biotechnology Research Center of the Guangdong Academy of Agricultural Sciences. This study has established a molecular link between members of the lacquer enzyme family and the brassinosteroid signaling pathway in plants, deepening our understanding of the precision, systematicity, and complexity of non-coding RNA regulatory networks.
MicroRNAs (miRNAs) primarily influence plant growth and development by regulating gene expression, leading to phenotypic changes and evolutionary processes. Plant lacquer enzymes, as an ancient protein family, have been reported to be involved in lignin synthesis, oxidation of phenolic compounds, and accumulation of reactive oxygen species.
In 2013, Professor Yueqin Chen's team at Sun Yat-sen University published an article in Nature Biotechnology, reporting a new function of lacquer enzyme protein: the lacquer enzyme gene OsLAC is regulated by miR397 and modulates rice yield by affecting the brassinosteroid signaling pathway. However, the exact mechanism by which lacquer enzymes influence brassinosteroid signaling transduction and rice yield was unclear.
In this study, researchers conducted biochemical and genetic analyses of OsLAC and found that the transthyretin-like (OsTTL) protein interacts with OsLAC and acts as a negative regulator of brassinosteroid signaling in rice. Overexpression of OsTTL in rice plants resulted in dwarfism, erect leaves, reduced grain size, and decreased yield, while knocking out the OsTTL gene led to increased grain size and yield. Interestingly, phosphorylation of the Ser226 site of the OsTTL protein is crucial for its degradation, and binding with OsLAC can protect OsTTL from phosphorylation-mediated protein degradation.
The study also revealed that the brassinosteroid signaling receptor protein OsBRI1 may be involved in the phosphorylation of the OsTTL protein. Further genetic complementation experiments showed that the grains of Osttl×OsBRI1-RNAi plants were significantly larger than those of OsBRI1-RNAi and wild-type plants, indicating that knocking out OsTTL effectively complemented the brassinosteroid-insensitive phenotype caused by OsBRI1 knockdown.
This study has established a direct link between lacquer enzyme proteins and brassinosteroid signaling, uncovering the molecular function of the miR397-OsLAC-OsTTL regulatory pathway. It holds promise for providing a material basis and theoretical support for crop genetic improvement and the breeding of new varieties.
For more information on the research paper, visit: https://doi.org/10.1093/plcell/koae147
