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- Title
Genetic Causes and Genomic Consequences of Breakdown of Distyly in Linum trigynum.
- Authors
Gutiérrez-Valencia, Juanita; Zervakis, Panagiotis-Ioannis; Postel, Zoé; Fracassetti, Marco; Losvik, Aleksandra; Mehrabi, Sara; Bunikis, Ignas; Soler, Lucile; Hughes, P William; Désamoré, Aurélie; Laenen, Benjamin; Abdelaziz, Mohamed; Pettersson, Olga Vinnere; Arroyo, Juan; Slotte, Tanja
- Abstract
Distyly is an iconic floral polymorphism governed by a supergene, which promotes efficient pollen transfer and outcrossing through reciprocal differences in the position of sexual organs in flowers, often coupled with heteromorphic self-incompatibility. Distyly has evolved convergently in multiple flowering plant lineages, but has also broken down repeatedly, often resulting in homostylous, self-compatible populations with elevated rates of self-fertilization. Here, we aimed to study the genetic causes and genomic consequences of the shift to homostyly in Linum trigynum , which is closely related to distylous Linum tenue. Building on a high-quality genome assembly, we show that L. trigynum harbors a genomic region homologous to the dominant haplotype of the distyly supergene conferring long stamens and short styles in L. tenue , suggesting that loss of distyly first occurred in a short-styled individual. In contrast to homostylous Primula and Fagopyrum , L. trigynum harbors no fixed loss-of-function mutations in coding sequences of S- linked distyly candidate genes. Instead, floral gene expression analyses and controlled crosses suggest that mutations downregulating the S- linked LtWDR-44 candidate gene for male self-incompatibility and/or anther height could underlie homostyly and self-compatibility in L. trigynum. Population genomic analyses of 224 whole-genome sequences further demonstrate that L. trigynum is highly self-fertilizing, exhibits significantly lower genetic diversity genome-wide, and is experiencing relaxed purifying selection and less frequent positive selection on nonsynonymous mutations relative to L. tenue. Our analyses shed light on the loss of distyly in L. trigynum , and advance our understanding of a common evolutionary transition in flowering plants.
- Subjects
GENETIC variation; WHOLE genome sequencing; GENE expression; FLOWERING of plants; GENOMICS; POLLINATORS; ANTHER
- Publication
Molecular Biology & Evolution, 2024, Vol 41, Issue 5, p1
- ISSN
0737-4038
- Publication type
Article
- DOI
10.1093/molbev/msae087