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Dryad

CYCLOIDEA paralogs function redundantly to specify dorsal flower development in Mimulus lewisii (Phrymaceae)

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Sep 18, 2023 version files 48.44 KB

Abstract

Premise: Duplicated genes (paralogs) are abundant in plant genomes and their retention may influence the function of genetic programs and contribute to evolutionary novelty. How gene duplication affects genetic modules, and the forces that contribute to paralog retention are outstanding questions. The CYCLOIDEA(CYC)-dependent flower symmetry program is a model for understanding the evolution of gene duplication, providing multiple examples of paralog partitioning and novelty. However, a novel CYC gene lineage duplication event near the origin of Higher Core Lamiales (HCL) has received little attention.

Methods: To understand the evolutionary fate of duplicated HCL CYC2 genes, we determined the effects on flower symmetry of suppressing MlCYC2A and MlCYC2B expression using RNA interference (RNAi). We determined flower symmetry phenotypic effects in single and double silenced backgrounds and coupled this with expression surveys of MlCYC2A, MlCYC2B, and a putative downstream RADIALIS (MlRAD5) ortholog.

Key results: MlCYC2A and MlCYC2B jointly contribute to bilateral flower symmetry. MlCYC2B exhibits a clear dorsal flower identity function and may additionally function in carpel development.  MlCYC2A functions in establishing dorsal petal shape. Further, our results suggest an MlCYC2A–MlCYC2B regulatory interaction which may affect pathway homeostasis.

Conclusions: Our results suggest that Higher Core Lamiales-specific CYC paralogs may be selectively retained for their joint contribution to bilateral flower symmetry, similar to the independently-derived CYC paralogs in the Lamiales model for bilateral flower symmetry research, Antirrhinum majus (snapdragon).