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ARS Home » Pacific West Area » Pullman, Washington » Plant Germplasm Introduction and Testing Research » Research » Publications at this Location » Publication #409941
Research Project: Enhancing Resistance to Biotic and Abiotic Stresses in Alfalfa

Location: Plant Germplasm Introduction and Testing Research

Title: Structural reorganization in two alfalfa mitochondrial genome assemblies and mitochondrial evolution in Medicago species

Author
item HE, XIAOFAN - Beijing Forestry University
item ZHANG, XIAOPENG - Beijing Forestry University
item DENG, YANTIAN - Beijing Forestry University
item YANG, RUI - Beijing Forestry University
item Yu, Long-Xi
item JIA, SHANGANG - China Agricultural University
item ZHANG, TIEJUN - Beijing Forestry University

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2023
Publication Date: 12/11/2023
Citation: He, X., Zhang, X., Deng, Y., Yang, R., Yu, L., Jia, S., Zhang, T. 2023. Structural reorganization in two alfalfa mitochondrial genome assemblies and mitochondrial evolution in Medicago species. International Journal of Molecular Sciences. 24:17334. https://doi.org/10.3390/ijms242417334.
DOI: https://doi.org/10.3390/ijms242417334

Interpretive Summary: In this study, we investigated two mitochondrial genomes of alfalfa varieties of Zhongmu NO.1 (299,123 bp) and Zhongmu NO.4 (306,983 bp), using new generation sequencing technology. The comparison of genome assemblies revealed that the same number of mitochondrial genes existed in the two varieties. Additionally, large fragments of repetitive sequences were found underlying frequent mitochondrial recombination events. We observed the extensive transfer of mitochondrial DNA fragments into the nuclear genome of Zhongmu NO.4. Analysis of the two well-known mitochondrial genes, cox1 and rrn18s genes in 35 Medicago accessions revealed the presence of population-level sequence deletions and substitutions. We propose that mitochondrial structure reorganizations may contribute to alfalfa evolution.

Technical Abstract: Plant mitochondria are crucial in species evolution, phylogenetics, classification, and identification as maternal genetic material. However, numerous repetitive sequences, complex structures and a low number of genes in the alfalfa mitochondrial genome have hindered its complete assembly and related researches. In this study, we assembled two mitochondrial genome of alfalfa varieties of Zhongmu NO.1 (299,123 bp) and Zhongmu NO.4 (306,983 bp), based on a combination of PacBio, Illumina, and Hi-C sequences. The comparison of genome assemblies revealed that the same number of mitochondrial genes, including 33 protein-coding genes, 16 tRNA genes, and three rRNA genes existed in the two varieties. Additionally, large fragments of repetitive sequences were found underlying frequent mitochondrial recombination events. We observed the extensive transfer of mitochondrial fragments into the nuclear genome in Zhongmu NO.4. Analysis of the cox1 and rrn18s genes in 35 Medicago accessions revealed the presence of population-level deletions and substitutions in the rrn18s gene. We propose that mitochondrial structure reorganizations may contribute to alfalfa evolution.