Article

How far are we from unraveling self-incompatibility in grasses

Teagasc Crops Research Centre, Oak Park, Carlow, Ireland
New Phytologist (Impact Factor: 7.67). 02/2008; 178(4):740-53. DOI: 10.1111/j.1469-8137.2008.02421.x
Source: PubMed

ABSTRACT

The genetic and physiological mechanisms involved in limiting self-fertilization in angiosperms, referred to as self-incompatibility (SI), have significant effects on population structure and have potential diversification and evolutionary consequences. Up to now, details of the underlying genetic control and physiological basis of SI have been elucidated in two different gametophytic SI (GSI) systems, the S-RNase SI and the Papaver SI systems, and the sporophytic SI (SSI) system (Brassica). In the grass family (Poaceae), which contains all the cereal and major forage crops, SI has been known for half a century to be controlled gametophytically by two multiallelic and independent loci, S and Z. But still none of the gene products for S and Z is known and only limited information on related biochemical responses is available. Here we compare current knowledge of grass SI with that of other well-characterized SI systems and speculate about the relationship between SSI and grass SI. Additionally, we discuss comparative mapping as a tool for the further investigation of grass SI.

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Available from: Susanne Barth, Oct 17, 2014
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    • "As gametophytic SI has been reported in both diploid and polyploid species within the tribes Triticeae, Poeae, and Paniceae, and seems to be monophyletic in the Poaceae family (Yang, et al. 2008), our work will be of major significance for evolutionary studies of speciation in some of the most important crop species. In the long run, we envisage, on the basis of our findings, modelling the SI cascade in Poaceae species. "
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    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 multi-allelic and independent loci, S and Z. Despite intense research efforts over the last six decades, the genes underlying S and Z remain uncharacterised. 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 centimorgan. Of the eight genes co-segregating 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 genes showed a frame-shift 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 towards 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.
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    • "The self-incompatibility reaction occurs when both the S and the Z allele of the haploid pollen are matched by the S and Z alleles in the diploid pistil. At present the genes at S and Z have not been cloned, although candidate genes have been proposed(Shinozuka, H. et al. 2010, Yang, B. et al. 2008). Semi in-vivo pollinated pistils were flash frozen two hours after pollination with either compatible or incompatible pollen (Figure 1), and we compared their transcriptomes to the transcriptomes of unpollinated stigma collected at the same time. "
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    ABSTRACT: Here we report the draft genome sequence of perennial ryegrass (Lolium perenne), an economically important forage and turf grass species widely cultivated in temperate regions worldwide. It is classified along with wheat, barley, oats and Brachypodium distachyon in the Pooideae sub-family of the grass family (Poaceae). Transcriptome data was used to identify 28,455 gene models, and we utilize macro-co-linearity between perennial ryegrass and barley, and synteny within the grass family to establish a synteny-based linear gene order. The gametophytic self-incompatibility (SI) mechanism enables the pistil of a plant to reject self-pollen and therefore promote outcrossing. We have used the sequence assembly to characterise transcriptional changes in the stigma during pollination with both compatible and incompatible pollen. Characterisation of the pollen transcriptome identified homologs to pollen allergens from a range of species, many of which were expressed to very high levels in mature pollen grains, and potentially involved in the SI mechanism. The genome sequence provides a valuable resource for future breeding efforts based on genomic prediction, and will accelerate the development of varieties for more productive grasslands. This article is protected by copyright. All rights reserved.
    No preview · Article · Sep 2015 · The Plant Journal
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    • "In wheat fields, L. rigidum can cause yield reductions of more than 40% [22]. Like many other grass weeds, L. rigidum is an obligate out crosser with a gametophytically controlled self-incompatible reproduction system [23] [24]. "
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    ABSTRACT: Herbicide resistant weeds are becoming increasingly common, threatening global food security. Here, we present BrIFAR: a new model system for the functional study of mechanisms of herbicide resistance in grass weeds. We have developed a large collection of Brachypodium accessions, the BrI collection, representing a wide range of habitats. Wide screening of the responses of the accessions to four major herbicide groups (PSII, ACCase, ALS/AHAS and EPSPS inhibitors) identified 28 herbicide-resistance candidate accessions. Target-site resistance to PSII inhibitors was found in accessions collected from habitats with a known history of herbicide applications. An amino acid substitution in the psbA gene (serine264 to glycine) conferred resistance and also significantly affected the flowering and shoot dry weight of the resistant accession, as compared to the sensitive accession. Non-target site resistance to ACCase inhibitors was found in accessions collected from habitats with a history of herbicide application and from a nature reserve. In-vitro enzyme activity tests and responses following pre-treatment with malathion (a cytochrome-P450 inhibitor) indicated sensitivity at the enzyme level, and give strong support to diclofop-methyl and pinoxaden enhanced detoxification as NTS resistance mechanism. BrIFAR can promote better understanding of the evolution of mechanisms of herbicide resistance and aid the implementation of integrative management approaches for sustainable agriculture.
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