Significant progress in the identification of cucumber flower topping genes
Recently, Zhang Xiaolan's research group of the College of Horticulture of China Agricultural University, Weng Yiqun Research Group of the University of Wisconsin and the Wen Changlong Group of the Vegetable Research Center of the Beijing Academy of Agricultural and Forestry Sciences published in the Journal of Development Online entitled "CsTFL1 inhibits determinate growth and terminal flower formation through interaction with CsNOT2a in cucumber (Cucumis sativus L.)" research paper (DOI: 10.1242/dev.180166). In this study, a mutant material with limited growth of cucumber was used to accurately locate the key gene CsTFL1 (terminal flower 1), which controls the limited growth of cucumber. The mutation of this gene can lead to limited growth of cucumber, showing “flower topping”. "Phenomenon, therefore the CsTFL1 gene is called the flower topping gene.
China is the largest country in cucumber production, with an annual planting area of more than 19 million mu and a production of 67 million tons, but the average yield is less than one quarter of that of developed countries such as the Netherlands. Among them, flower topping is an important factor that severely restricts the production of cucumbers in winter and spring, with an average yield reduction of 30%, and severe production. Therefore, it is of great practical practical significance to excavate the topping gene of cucumber flower and study the molecular mechanism of flower topping. The joint research group took the lead in cloning the important gene CsTFL1, which controls the flowering of cucumber, and found that the amino acid change caused by a single base mutation of the gene is the key to flower topping. Using cucumber genetic transformation system, RNAi interference with CsTFL1 gene expression can also lead to flower topping phenotype, and CsTFL1 can complement the phenotype of plant Arabidopsis thaliana "flower topping" mutant tfl1, which proves that CsTFL1 inhibits flowering and Induces the function of flower topping.
The TFL1 gene has been generally confirmed as a flowering suppressor gene in model plant species. Studies have shown that it can compete with the flowering gene FT to compete with the flowering gene FT for the same flowering transcription factor FD to exercise its inhibitory flowering function. However, the joint research team found that the CsTFL1 gene in cucumber differs from the TFL1 molecule in Arabidopsis and rice, and cannot directly interact with the flowering transcription factor CsFD protein in cucumber to inhibit flowering gene expression (Arabidopsis model). It is also not possible to interact with FD protein via 14-3-3 protein linkage (rice model). However, the flowering gene CsFT in cucumber can directly interact with the flowering transcription factor CsFD protein, and CsFD can interact with 14-3-3 protein.
Furthermore, the joint research team used cDNA library to identify a key protein CsNOT2a that interacts with cucumber CsTFL1. Further studies revealed that the gene can be linked to CsTFL1 and an FDP (FD PARALOG) protein. The FDP protein and the FD protein belong to the bZIP transcription factor family and have the function of regulating downstream flowering genes. Therefore, the joint research team mapped the flowering activation complex (CsFT-CsFD-Cs1433) and the flowering inhibition complex model (CsTFL1-CsNOT2a-CsFDP) in cucumber, and concluded that the two types of complexes compete to regulate the downstream flowering gene CsAP1. CsLFY, etc. to regulate the formation of cucumber flower topping. The conclusion of this study can lay an important foundation for the use of genetic improvement to create new varieties of cucumber resistant to flower topping. It can also provide important reference for the research of flower topping prevention of other melon crops and provide new ideas for studying the molecular mechanism of TFL1.
The work was funded by the National Natural Science Foundation of China, the Beijing Natural Science Foundation, the Beijing Science and Technology New Star and the ‘Training Crop Development Physiology and Quality Control’ 111. Dr. Wen Changlong from the Vegetable Research Center of the Beijing Academy of Agricultural and Forestry Sciences, Dr. Zhao Wensheng from the China Agricultural University (now working at Hebei Agricultural University) and Liu Wei, a research assistant at the Wen Changlong Group, are the co-first authors. Professor Zhang Xiaolan from China Agricultural University and Professor Weng Yiqun from the University of Wisconsin, USA.
