Promoter insertion leads to polyembryony in mango - a case of convergent evolution with citrus

Abstract

Sexual reproduction in plants is the main pathway for creating new genetic combinations in modern agriculture. In heterozygous plants, after the identification of a plant with desired traits, vegetative propagation (cloning) is the primary path to create genetically uniform plants. Another natural plant mechanism that creates genetically uniform plants (clones) is apomixis. In fruit crops like citrus and mango, sporophytic apomixis results in polyembryony, where seeds contain multiple embryos, one of which is sexually originated and the others are vegetative clones of the parent mother tree. Utilizing the mango genome and genetic analysis of a diverse germplasm collection, we identified MiRWP as the gene that causes polyembryony in mango. There is a strong correlation between a specific insertion in the gene’s promoter region and altered expression in flowers and developing fruitlets, inducing multiple embryos. The MiRWP gene is an ortholog of CitRWP that causes polyembryony in citrus. Based on the data, we speculate that promoter insertion events, which occurred independently in citrus and mango, induced nucellar embryogenesis. The results suggest convergent evolution of polyembryony in the two species. Further work is required to demonstrate the utility of these genes (mango and citrus) in other biological systems as a tool for the clonal production of other crops.

Acknowledgements

The research was supported by Research Grant No. IS-5106-18R from BARD, The United States–Israel Binational Agricultural Research and Development Fund (granted to A.S., D.N.K., Y.C., and R.O.), and by grants No. 203-0859 (granted to A.S. and R.O.) and No. 203-0110 (granted to Y.C.) from the Chief Scientist of the Israeli Ministry of Agriculture. D.N.K. was supported by a grant from the USDA National Institute of Food and Agriculture (USDA-NIFA 2018-51181-28375).

Author contributions

Y.C. and A.S. conceived the idea, coordinated the research, and wrote the paper. C.B.Y. performed the cytology and gene expression analysis and was part of the mapping work. A.R. performed DNA and genotyping analyses. R.E. - sample collection and DNA preps. M.I.S. - germplasm collection phenotyping, sample collection. A.F. - bioinformatics SNP discovery. N.D. and I.B. - germplasm phenotyping, DNA preparation genomic analysis, and writing of the paper. M.W. - genome of KP chloroplast insertion. D.K. - conceived the idea of working on the trait, writing the paper. R.O. - synteny analysis with Citrus.

Data availability

The data underlying this article are available in the article and its online supplementary material.

Conflict of interest statement

None declared.

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