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


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
    • "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.
    The Plant Journal 09/2015; DOI:10.1111/tpj.13037 · 5.97 Impact Factor
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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.
    Plant Science 12/2014; 229:43–52. DOI:10.1016/j.plantsci.2014.08.013 · 3.61 Impact Factor
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    • "There are certain physiological characteristics of grass SI that resemble features of the Papaver system and Brassica SSI including the dry stigma type and a rapid response to stigma-pollen interactions [14]. In these three SI systems, the stigmas critically discriminate between compatible and incompatible pollen grains and promote compatible pollen growth while preventing incompatible pollen adhesion, hydration, germination or invasion. "
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    ABSTRACT: Background Many Poaceae species show a gametophytic self-incompatibility (GSI) system, which is controlled by at least two independent and multiallelic loci, S and Z. Until currently, the gene products for S and Z were unknown. Grass SI plant stigmas discriminate between pollen grains that land on its surface and support compatible pollen tube growth and penetration into the stigma, whereas recognizing incompatible pollen and thus inhibiting pollination behaviors. Leymus chinensis (Trin.) Tzvel. (sheepgrass) is a Poaceae SI species. A comprehensive analysis of sheepgrass stigma transcriptome may provide valuable information for understanding the mechanism of pollen-stigma interactions and grass SI. Results The transcript abundance profiles of mature stigmas, mature ovaries and leaves were examined using high-throughput next generation sequencing technology. A comparative transcriptomic analysis of these tissues identified 1,025 specifically or preferentially expressed genes in sheepgrass stigmas. These genes contained a significant proportion of genes predicted to function in cell-cell communication and signal transduction. We identified 111 putative transcription factors (TFs) genes and the most abundant groups were MYB, C2H2, C3H, FAR1, MADS. Comparative analysis of the sheepgrass, rice and Arabidopsis stigma-specific or preferential datasets showed broad similarities and some differences in the proportion of genes in the Gene Ontology (GO) functional categories. Potential SI candidate genes identified in other grasses were also detected in the sheepgrass stigma-specific or preferential dataset. Quantitative real-time PCR experiments validated the expression pattern of stigma preferential genes including homologous grass SI candidate genes. Conclusions This study represents the first large-scale investigation of gene expression in the stigmas of an SI grass species. We uncovered many notable genes that are potentially involved in pollen-stigma interactions and SI mechanisms, including genes encoding receptor-like protein kinases (RLK), CBL (calcineurin B-like proteins) interacting protein kinases, calcium-dependent protein kinase, expansins, pectinesterase, peroxidases and various transcription factors. The availability of a pool of stigma-specific or preferential genes for L. chinensis offers an opportunity to elucidate the mechanisms of SI in Poaceae. Electronic supplementary material The online version of this article (doi: 10.1186/1471-2164-15-399) contains supplementary material, which is available to authorized users.
    BMC Genomics 05/2014; 15(1):399. DOI:10.1186/1471-2164-15-399 · 3.99 Impact Factor
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