Convergence and constraint in glucosinolate evolution across the Brassicaceae.

Area of Science:

• Plant biochemistry and molecular evolution
• Chemical ecology and plant-environment interactions
• Genomics and phylogenetics

Background:

• Plant specialized metabolites are crucial for plant-environment interactions, with diversity arising from genomic events.
• Evolutionary patterns shaping chemical diversity within plant families are less understood.
• The aliphatic glucosinolate pathway and its terminal modification enzyme, GSL-OH, provide a model for studying this diversity.

Purpose of the Study:

• To investigate the evolution of GSL-OH genes within the Brassicaceae family.
• To understand the genomic processes driving the presence-absence variation of specific glucosinolate products.
• To determine the functional and ecological significance of GSL-OH enantiomers.

Main Methods:

• Phylogenetic and functional analysis of GSL-OH orthologs across Brassicaceae.
• Mapping the genomic origin and evolutionary trajectory of the GSL-OH locus.
• Bioassays including Trichoplusia ni larval choice assays and Botrytis cinerea resistance tests.

Main Results:

• A complex evolutionary history for GSL-OH involving multiple ancestral loci and extensive gene loss was uncovered.
• Convergent evolution of enantiomeric specificity (R vs. S) was observed in independent tandem duplicates.
• Differential susceptibility to herbivory (T. ni) and disease (B. cinerea) was linked to specific GSL-OH enantiomers.

Conclusions:

• Recurrent gene loss and complex origins shape GSL-OH diversity in Brassicaceae.
• Enantiomeric specificity of glucosinolates influences plant defense strategies against different antagonists.
• Understanding GSL-OH evolution provides insights into the diversification of plant chemical defenses.