Identification and Expression of the MADS-box Gene Family in Different Versions of the Ginkgo biloba Genome

MADS-box transcription factors play important roles in many organisms. These transcription factors are involved in processes such as the formation of the flower organ structure and the seed development of plants. Ginkgo biloba has two genome versions (version 2019 and version 2021), and there is no analysis or comparison of the MADS-box gene family in these two genomes. In this study, 26 and 20 MADS-box genes were identified from the two genomes of Ginkgo, of which 12 pairs of genes reached more than 80% similarity. According to our phylogenetic analysis results, we divided these genes into type I (Mα and Mγ subfamilies) and type II (MIKC and Mδ subfamilies) members. We found that both sets of genomes lacked the Mβ gene, while the MIKC gene was the most numerous. Further analysis of the gene structure showed that the MIKC genes in the two genomes had extralong introns (≥20 kb); these introns had different splicing patterns, and their expression might be more abundant. The gene expression analysis proved that GbMADS genes were expressed to varying degrees in eight Ginkgo biological tissues. Type II GbMADS genes not only were found to be related to female flower bud differentiation and development but also are important in seed development. Therefore, MADS-box genes may play important roles in the development of Ginkgo reproductive organs, which may suggest a genetic role in sexual differentiation. This study further contributes to the research on MADS-box genes and provides new insights into sex determination in Ginkgo.