# Characterization and Phylogenetic Analysis of MADS-Box Gene Family in Magnoliids: Insights into the Evolution of Floral Morphogenesis in Angiosperms

## TL;DR

This study explores the evolution of MADS-box genes in magnoliids, revealing insights into how flowers evolved in flowering plants.

## Contribution

The study identifies MADS-box gene expansion mechanisms and floral homeotic genes in magnoliids, linking them to ancestral angiosperm models.

## Key findings

- MADS-box gene expansion in magnoliids is primarily due to whole-genome duplication events.
- Floral homeotic MADS-box genes in Liriodendron chinensis and Chimonanthus praecox are orthologous to ABCDE model genes.
- Expression patterns of MADS-box genes support the 'shifting−fading borders' model in basal angiosperms.

## Abstract

Magnoliids represent one of the most basal lineages within angiosperms, and their ancestral floral morphology provides crucial insights into the evolution of flowers in angiosperms. MCM1-AGAMOUS-DEFICIENS-SRF (MADS)-box transcription factors play crucial roles in specifying floral organs. To understand their evolutionary history and functional divergence in magnoliids, we identified MADS-box genes, and conducted phylogenetic and expression analysis in 33 magnoliids and 8 other angiosperm plants. A total of 1310 MADS-box genes were identified and classified into Type I and Type II. The expansion of MADS-box genes in magnoliids mainly arose from whole-genome duplication events. In Liriodendron chinensis and Chimonanthus praecox, we identified floral homeotic MADS-box genes that are orthologous to the ABCDE model genes of floral organ identity determination. The broad expression pattern of A and B genes in floral organs and overlapping activity of ABCDE-model genes are consistent with the “shifting−fading borders” scheme proposed in basally diverging angiosperm lineages. Our results not only elucidate the driving forces underlying the diversification of MADS-box genes in magnoliids, but also shed light on the evolutionary models of floral development in angiosperms.