Identification of genes related to self-incompatibility in ryegrass (Lolium perenne L.)

Self-incompatibility (SI) is a mechanism that prevents self-pollination and inbreeding in many flowering plant species. SI in Lolium perenne is controlled by two multi-allelic loci, S and Z. The working of this SImechanism has important consequences for L. perenne breeding as it prevents the efficient production of inbred lines and hybrids. The aim of this study was to identify genes involved in the SI-response in L. perenne. Therefore, different approaches were applied. We investigated first whether homologues of genes involved in the SI-response of other plant families and grass species (Solanaceae, Brassicaceae and Phalaris coerulescens) are also present in L. perenne. Based on the results, we could conclude that no S-RNase based system (active in members of the Solanaceae) is present in ryegrass. This result was not surprising as very little features with regards to the SI-response are common for grasses and species displaying a S-RNase based system. On the other hand, a L. perenne homologue of SRK, the key component at the female side in members of the Brassicaceae, was identified. However, this gene was not only expressed in pistils but also in leaves indicating that it is not the recognition factor of the SI-response in ryegrass. This conclusion was also supported by its map position, as it mapped on LG4 and not on LG1 or LG2, where S and Z are located. Finally, we amplified in pistils and leaves of L. perenne the thioredoxin homologue known to be involved in the SI-response of Phalaris coerulescens, also a member of the Poaceae. The L. perenne thioredoxin homologue mapped in the neighbourhood of S (at 3cM), indicating that it is not S. Whether this thioredoxin gene is involved in the SI-response in ryegrass needs to be investigated. However, the involvement of thioredoxins in SI has been demonstrated in Brassica. Another objective of this study was to identify genes involved in the signalling cascade triggered by a SI-response in L. perenne. Therefore we used two differential expression techniques: cDNA-AFLP and the cDNAmicroarray. The genome-wide expression analysis carried out by cDNAAFLP allowed us to identify 479 TDFs (Transcript Derived Fragments) as putatively related to SI in L. perenne. All the expression profiles were quantified using AFLP Quantar Pro and clustered into groups of co-regulated genes. A subset of these genes was selected to study further. The selected genes clustered into 11 functional categories. Several of them corresponded to genes involved in general cellular processes but homology was also been found to proteins known to be involved in fertilization and SI-processes in other plant families such as ubiquitin-related and calcium-related proteins. The GRASP microarray was used to confirm the expression profiles of the TDFs selected by the cDNA-AFLP and to identify other genes related to SI. This microarray contains the TDFs selected by cDNA-AFLP and cDNA clones of genes involved in different biological processes. Using this technique, we were able to identify 371 differentially expressed genes putatively involved in the SI-response. Surprisingly the results from both techniques were contradictory. Confirmation of a selection of genes by Realtime RT-PCR revealed consistency between the results of Real-time RTPCR and those of the cDNA-AFLP but not with those of the microarray. Further investigation is needed to clarify this point. As a complementary approach, the genome location of the genes identified as putatively involved in SI was determined. Two mapping populations were used for this purpose: the ILGI population and the CLODvP population. Some of the mapped genes clustered around S and Z on LG1 and LG2, respectively. Several other markers mapped across the different linkage groups with a higher concentration on LG3 and LG4. Also a strong association was identified between LG1 and LG3 indicating that some genes of LG3 interact with LG1 during SI. Finally, combining all these data, a selection of 21 genes putatively involved in SI in L. perenne was made. Confirmation of their involvement is the subject for further research.

Grantor dc:publisher

Ghent University. Faculty of Bioscience Engineering

Year dc:date

2005

Author dc:creator

• Van Daele, Inge

Contributors dc:contributor

• Van Bockstaele, Erik
• Roldán-Ruiz, Isabel

• Biology and Life Sciences

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://biblio.ugent.be/publication/468706
urn:isbn:9789059890930
https://biblio.ugent.be/publication/468706/file/1877707

OAI identifier oai:identifier

oai:archive.ugent.be:468706