SLTAB2 is the paramutated SULFUREA locus in tomato

Area of Science:

• Plant genetics
• Epigenetics
• Molecular biology

Background:

• The sulfurea (sulf) allele in tomato (Solanum lycopersicum) is a silent epigenetic variant impacting pigment production.
• Paramutation, the transfer of a silenced state between alleles, is observed in sulf/+ heterozygotes, leading to chlorotic sectors due to wild-type allele silencing.

Purpose of the Study:

• To elucidate the molecular mechanism underlying paramutation in tomato.
• To identify the gene responsible for the sulfurea phenotype and investigate its role in paramutation.

Main Methods:

• Gene mapping to identify the SULFUREA locus.
• Analysis of DNA methylation and small interfering RNA (siRNA) production at the promoter region.
• Virus-induced gene silencing (VIGS) to assess gene function and phenocopy the sulfurea mutant.

Main Results:

• The SULFUREA gene was mapped to SLTAB2, an orthologue of an Arabidopsis gene involved in photosystem I translation.
• Paramutation of SLTAB2 was associated with increased DNA methylation and siRNA production at its promoter.
• Virus-induced gene silencing of SLTAB2 successfully phenocopied the sulfurea mutation.

Conclusions:

• siRNAs likely mediate the paramutation of SULFUREA in tomato.
• Unlike maize systems, tomato paramutagenicity is not linked to repetitive sequences at the siRNA production or DNA methylation sites.