A Gene Encoding a DUF247 Domain Protein Cosegregates with theSSelf-Incompatibility Locus in Perennial Ryegrass

Abstract

The grass family (Poaceae), the fourth largest family of flowering plants, encompasses the most economically important cereal, forage, and energy crops, and exhibits a unique gametophytic self-incompatibility (SI) mechanism that is controlled by at least two multiallelic and independent loci, S and Z. Despite intense research efforts over the last six decades, the genes underlying S and Z remain uncharacterized. Here, we report a fine-mapping approach to identify the male component of the S-locus in perennial ryegrass (Lolium perenne L.) and provide multiple evidence that a domain of unknown function 247 (DUF247) gene is involved in its determination. Using a total of 10,177 individuals from seven different mapping populations segregating for S, we narrowed the S-locus to a genomic region containing eight genes, the closest recombinant marker mapping at a distance of 0.016 cM. Of the eight genes cosegregating with the S-locus, a highly polymorphic gene encoding for a protein containing a DUF247 was fully predictive of known S-locus genotypes at the amino acid level in the seven mapping populations. Strikingly, this gene showed a frameshift mutation in self-compatible darnel (Lolium temulentum L.), whereas all of the self-incompatible species of the Festuca-Lolium complex were predicted to encode functional proteins. Our results represent a major step forward toward understanding the gametophytic SI system in one of the most important plant families and will enable the identification of additional components interacting with the S-locus.

Inheritance patterns of the response to in vitro doubled haploid induction in perennial ryegrass (Lolium perenne L.)

“…Simple sequence repeat (SSR) markers G05_065 and G05_134 (Studer et al 2008) and high resolution melting curve analysis (HRM) marker 05_02833 (Manzanares et al 2016), selected because of their heterozygosity in a large number of anther donor genotypes, were used to characterize the green regenerants. A detailed primer description and the PCR amplification protocol used for the SSR markers can be found in Studer et al (2008).…”

“…Amplification products were separated, visualised and scored using an ABI 3130 16 capillary electrophoresis system (Applied Biosystems, Foster City, CA, USA) and the GeneMarker software version 1.5 (SoftGenetics, PA, USA). HRM analysis was performed as described in Studer et al (2009) and Manzanares et al (2016). Briefly, PCR amplicons were melted between 60 and 98 °C using a 96-well LightScanner and genotyping was performed with the LightScanner software package (BioFire Diagnostics, UT, USA).…”

Grass blindness

“…Introgression of autogamy from L. temulentum into the genetic backgrounds of allogamous Lolium and Festuca species has opened the way to mapping genetic loci that control self-incompatibility (Do Canto, Studer, & Lubberstedt, 2016;Thorogood & Hayward, 1992). In an important recent advance, the S-locus of obligately outbreeding Lolium perenne has been associated with a gene (functional identity not yet established) which, in self-compatible L. temulentum, has a frameshift mutation disrupting 24 amino acids at the C-terminus (Manzanares et al, 2016).…”

Sex chromosome evolution via two genes

“…Little is known about the mode of action of the SOFF protein, other than it containing a PFAM annotation "Domain of Unknown Function 247 (DUF247)". Intriguingly, a DUF247 domaincontaining protein cosegregates with the S SelfIncompatibility locus in perennial ryegrass ( 22 ) , hinting at the possibility of a conserved potential pistil suppression function. To clarify the spatial expression patterns of both genes to better elucidate their respective functions, singlemolecule fluorescence in situ hybridization (smFISH) was used to track the expression and localization of the sexdetermination genes on XX and YY spear tips.…”