A Change inSHATTERPROOFProtein Lies at the Origin of a Fruit Morphological Novelty and a New Strategy for Seed Dispersal inMedicagoGenus    

Abstract

Angiosperms are the most diverse and numerous group of plants, and it is generally accepted that this evolutionary success owes in part to the diversity found in fruits, key for protecting the developing seeds and ensuring seed dispersal. Although studies on the molecular basis of morphological innovations are few, they all illustrate the central role played by transcription factors acting as developmental regulators. Here, we show that a small change in the protein sequence of a MADS-box transcription factor correlates with the origin of a highly modified fruit morphology and the change in seed dispersal strategies that occurred in Medicago, a genus belonging to the large legume family. This protein sequence modification alters the functional properties of the protein, affecting the affinities for other protein partners involved in high-order complexes. Our work illustrates that variation in coding regions can generate evolutionary novelties not based on gene duplication/subfunctionalization but by interactions in complex networks, contributing also to the current debate on the relative importance of changes in regulatory or coding regions of master regulators in generating morphological novelties.

Pod shattering resistance associated with domestication is mediated by a NAC gene in soybean

“…In Arabidopsis and its relatives in Brassicaceae, the mutants or natural variants with indehiscent fruit are frequently related to the loss-of-function or loss-of-expression of genes involved in the regulation of cell identity of lignified valve margin and ALs 26,55,56 . In the legume plant Medicago, a coding change in SHP orthologs is recently found to be correlative with the origin of the specialized coiled morphology of the indehiscent fruit, but the exact cellular and genetic basis of such fruit indehiscence is still unknown 57 . Our findings represent a causative mechanism for pod shattering resistance, particularly applicable to this eudicot crop with fundamentally different fruit structures from both cereals and Arabidopsis.…”

MADSreloaded: evolution of theAGAMOUSsubfamily genes

“…Conversely, a variation in the Medicago truncatula SHP homologue protein, MtruSHP, strengthened its interaction with SEP3 in yeast and was associated with the coiled fruit formation observed in this and related species. Other Medicago species having the threonine residue develop uncoiled pods (Fourquin et al ., ). This threonine‐to‐alanine variation is located in the C terminus immediately upstream of the conserved AG motif I that was identified by Kramer et al .…”

Protein change in plant evolution: tracing one thread connecting molecular and phenotypic diversity

“…In the genus Medicago (Fabaceae), a major difference in fruit morphology is correlated with a similar single amino acid insertion into SHATTERPROOF (SHP)-like MADS box proteins. Rather than disrupting PPIs, however, the amino acid insertion may strengthen the interaction between Medicago SHP and SEP3 homologs (Fourquin et al, 2013). …”