# Genome-Wide Analysis Unveils the Evolutionary Impact of Allopolyploidization on the 14-3-3 Gene Family in Rapeseed (Brassica napus L.)

## TL;DR

This study explores how the 14-3-3 gene family in rapeseed evolved after polyploidization, revealing changes in gene structure, regulation, and expression.

## Contribution

The study provides a comprehensive analysis of the evolutionary impact of allopolyploidization on the 14-3-3 gene family in Brassica napus.

## Key findings

- Allopolyploidization led to the loss of some collinear 14-3-3 genes in B. napus.
- The 14-3-3 gene family in B. napus shows increased regulatory complexity due to additional cis-acting elements.
- Gene expression patterns of GRF2 homologs changed after allopolyploidization.

## Abstract

Background: Polyploidization drives the formation and evolution of angiosperms, profoundly reshaping genomic architecture and function. The 14-3-3 proteins (also known as G-box binding regulators, GRFs) are conserved signaling molecules involved in a range of physiological processes, including developmental signaling and stress responses. Elucidating the evolutionary trajectories of 14-3-3 genes in Brassica napus following allopolyploidization is critical for understanding polyploid crop evolution and developing molecular breeding strategies for improved stress resistance and yield. Results: In this study, forty-eight orthologous 14-3-3 genes were identified in the genome of B. napus, and twenty-two orthologous 14-3-3 genes were found in the genomes of both Brassica rapa and Brassica oleracea. Gene mapping analysis indicated that 14-3-3 genes were broadly distributed across all chromosomes; however, they exhibited significant heterogeneity. Phylogenetic tree construction revealed that 14-3-3 genes can be categorized into two groups: epsilon and non-epsilon genes. Gene structure analysis showed that most non-epsilon genes contain 3-4 exons, while most epsilon genes contain 5-7 exons. Collinearity analysis identified 36 orthologous gene pairs between the A (B. rapa) and C genomes (B. oleracea) but only 28 paralogous gene pairs within the A and C subgenomes of B. napus, indicating that some collinear 14-3-3 genes were lost during allopolyploidization. The Ka/Ks ratios (ratio of non-synonymous to synonymous substitution rate) of the 61 identified duplicated gene pairs were all less than 1, suggesting that these genes underwent purifying selection. Promoter analysis indicated that the average number of cis-acting elements in B. napus 14-3-3 genes was one more than in B. rapa and B. oleracea, implying that allopolyploidization increased the regulatory complexity of 14-3-3 genes. Tissue expression profiling demonstrated that the expression pattern of GRF2 homologs was altered after allopolyploidization. Conclusions: By systematically investigating the copy number, genomic distribution, structure, evolutionary relationships, and expression patterns of 14-3-3 genes in B. napus and its progenitors, this study enhances our understanding of how allopolyploidization promotes gene family evolution.