Polyploidization-driven differentiation of freezing tolerance in Solidago canadensis

Area of Science:

• Plant biology
• Genetics
• Evolutionary biology

Background:

• Solidago canadensis (Canada goldenrod) has expanded from temperate to subtropical regions via polyploidization.
• Polyploidization, the increase in the number of sets of chromosomes, can affect plant traits and adaptation.

Purpose of the Study:

• To investigate the impact of polyploidization on the freezing tolerance of Solidago canadensis.
• To explore the underlying genetic and epigenetic mechanisms, specifically focusing on the ScICE1 gene and DNA methylation.

Main Methods:

• Assessed freezing tolerance by measuring the LT50 (temperature causing 50% cell rupture) across 35 Solidago canadensis populations.
• Quantified ScICE1 gene copy number and expression levels in diploid and polyploid populations.
• Analyzed DNA methylation patterns in the ScICE1 gene promoter region.

Main Results:

• Freezing tolerance decreased significantly with increasing ploidy levels in Solidago canadensis.
• Polyploid populations exhibited lower ScICE1 gene expression but higher gene copy numbers compared to diploids.
• Increased DNA methylation in the ScICE1 promoter was observed in polyploids, correlating with reduced gene expression.

Conclusions:

• Promoter DNA methylation represses the expression of multi-copy ScICE1 genes in polyploid Solidago canadensis, leading to reduced freezing tolerance.
• DNA methylation plays a crucial role in regulating gene expression across multiple gene copies.
• This study provides evidence for polyploidization-driven adaptation, mediated by epigenetic regulation, in Solidago canadensis expanding into new environments.