Search

Perennial ryegrass (Lolium perenne L.) is the principal forage grass utilized in Danish agriculture and underpins the beef and dairy sectors. It is characterized as having high digestibility, high nutritional value, and high productivity during vegetative growth. However, at the reproductive growth stage there is a significant reduction in digestibility due to an increase in the stem to leaf ratio. Thus, the controlled inhibition or delay of flowering would result in a significant increase of forage quality. Traditional breeding programs have been successfully breeding new varieties of perennial ryegrass for decades. However, it can take more than ten years to develop a new variety and involves intensive phenotyping at all stages of selection. It is envisaged that with the aid of molecular markers, breeding programs can be accelerated and gains increased. Our goal is to develop and validate functional molecular markers suitable for marker-assisted breeding for delayed flowering time in perennial ryegrass. We are particularly interested in the changes in the transcriptome of perennial ryegrass during the induction of flowering, which we are investigating using an RNA-Seq approach. Candidate genes will be converted to molecular markers and mapped in an existing mapping population previously characterized for flowering time and vernalization response. References: Amasino, R.M., Michaels S.D. (2010). The Timing of Flowering. Plant Physiology 154: 516–520 Greenup, A., W. Peacock, W.J., Dennis E.S., Trevaskis, B. (2009). The molecular biology of seasonal flowering-responses in Arabidopsis and the cereals. Annals of Botany 103: 1165–1172 Distelfeld, A.,Li, C., Dubcovsky J. (2009). Regulation of flowering in temperate cereals. Current Opinion in Plant Biology 12:178–184 Jung, C., Müller, A.E. (2009). Flowering time control and applications in plant breeding. Trends in Plant Science 14 /10: 563-573 Andersen, J.L., Jensen, L.B., Asp, T., Lübberstedt, T. (2006). Vernalization response in perennial ryegrass (Lolium perenne L.) involves orthologues of diploid wheat (Triticum monococcum) VRN1 and rice (Oryza sativa) Hd1. Plant Molecular Biology 60: 481-494 Perennial ryegrass (Lolium perenne L.) is the principal forage grass utilized in Danish agriculture and underpins the beef and dairy sectors. It is characterized as having high digestibility, high nutritional value, and high productivity during vegetative growth. However, at the reproductive growth stage there is a significant reduction in digestibility due to an increase in the stem to leaf ratio. Thus, the controlled inhibition or delay of flowering would result in a significant increase of forage quality. Traditional breeding programs have been successfully breeding new varieties of perennial ryegrass for decades. However, it can take more than ten years to develop a new variety and involves intensive phenotyping at all stages of selection. It is envisaged that with the aid of molecular markers, breeding programs can be accelerated and gains increased. Our goal is to develop and validate functional molecular markers suitable for marker-assisted breeding for delayed flowering time in perennial ryegrass. We are particularly interested in the changes in the transcriptome of perennial ryegrass during the induction of flowering, which we are investigating using an RNA-Seq approach. Candidate genes will be converted to molecular markers and mapped in an existing mapping population previously characterized for flowering time and vernalization response. References: Amasino, R.M., Michaels S.D. (2010). The Timing of Flowering. Plant Physiology 154: 516–520 Greenup, A., W. Peacock, W.J., Dennis E.S., Trevaskis, B. (2009). The molecular biology of seasonal flowering-responses in Arabidopsis and the cereals. Annals of Botany 103: 1165–1172 Distelfeld, A.,Li, C., Dubcovsky J. (2009). Regulation of flowering in temperate cereals. Current Opinion in Plant Biology 12:178–184 Jung, C., Müller, A.E. (2009). Flowering time control and applications in plant breeding. Trends in Plant Science 14 /10: 563-573 Andersen, J.L., Jensen, L.B., Asp, T., Lübberstedt, T. (2006). Vernalization response in perennial ryegrass (Lolium perenne L.) involves orthologues of diploid wheat (Triticum monococcum) VRN1 and rice (Oryza sativa) Hd1. Plant Molecular Biology 60: 481-494

Timothy (Phleum pratense L.) is the major forage species within the genus Phleum and is widely grown in cool-season regions of the world, including the Nordic countries. Most temperate perennial grasses have a dual induction requirement for flowering. Primary induction is achieved by a prolonged period of low temperature, i.e., vernalization, and/or short days, while secondary induction requires transition to long days and increased temperatures. While induction of flowering in timothy requires secondary induction, a vernalization response has not previously been reported for this species. We studied the vernalization response in 38 genotypes of diverse geographic origin and found that vernalization accelerated heading in all genotypes. In addition, considerable variation in the vernalization response was observed between genotypes and a requirement for vernalization to induce flowering was indicated in genotypes of Northern origin. While heading time in general was found to be correlated to geographic origin of genotypes, a strong vernalization response was identified in genotypes of contrasting geographic origin. Candidate genes for the vernalization response genes VRN1, VRN2 and VRN3 (also named FT) were identified and transcript analysis during primary and secondary induction showed that VRN1 transcription was induced by vernalization. However, when not vernalized, genotypes with a strong vernalization response showed a prolonged repression of VRN1 transcription throughout secondary induction. In contrast, in genotypes with a mild vernalization response VRN1 transcription was induced by transfer to secondary induction. We conclude that significant genetic variation for the vernalization response is present within timothy and suggest that differential regulation of VRN1 transcription discriminates genotypes with contrasting vernalization responses. Timothy (Phleum pratense L.) is the major forage species within the genus Phleum and is widely grown in cool-season regions of the world, including the Nordic countries. Most temperate perennial grasses have a dual induction requirement for flowering. Primary induction is achieved by a prolonged period of low temperature, i.e., vernalization, and/or short days, while secondary induction requires transition to long days and increased temperatures. While induction of flowering in timothy requires secondary induction, a vernalization response has not previously been reported for this species. We studied the vernalization response in 38 genotypes of diverse geographic origin and found that vernalization accelerated heading in all genotypes. In addition, considerable variation in the vernalization response was observed between genotypes and a requirement for vernalization to induce flowering was indicated in genotypes of Northern origin. While heading time in general was found to be correlated to geographic origin of genotypes, a strong vernalization response was identified in genotypes of contrasting geographic origin. Candidate genes for the vernalization response genes VRN1, VRN2 and VRN3 (also named FT) were identified and transcript analysis during primary and secondary induction showed that VRN1 transcription was induced by vernalization. However, when not vernalized, genotypes with a strong vernalization response showed a prolonged repression of VRN1 transcription throughout secondary induction. In contrast, in genotypes with a mild vernalization response VRN1 transcription was induced by transfer to secondary induction. We conclude that significant genetic variation for the vernalization response is present within timothy and suggest that differential regulation of VRN1 transcription discriminates genotypes with contrasting vernalization responses.

Laccases are multicopper oxidases capable of polymerizing monolignols. Histochemical assays have shown temporal and spatial correlation with secondary cell wall formation in both herbs and woody perennials. However, in plants laccases constitutes a relatively large group of isoenzymes with unique substrate specificities and expression patterns. As part of the strategic research centre Bio4Bio, the present project deals with laccase functions in relation to cell wall formation in grasses based on a study of the model species Brachypodium distachyon. Thirty-one isozymes have been retrieved from the recently published genome. Histochemical assays show high correlation between lignification and laccase-like activity in this species. Temporal and spatial correlation between these processes will be further studied by analysis of gene expression based on quantitative PCR and fluorescent in situ hybridization. Specific isozymes that show high correlation with the process of secondary cell wall formation will be further studied in a reverse genetic study in which candidates will be knocked out using RNA interference. Phenotypes of knock-out mutants are to be described in relation to cell wall degradability in order to reveal possible gains for saccharification of grass-derived feedstocks in bioethanol production and industrial processing. Laccases are multicopper oxidases capable of polymerizing monolignols. Histochemical assays have shown temporal and spatial correlation with secondary cell wall formation in both herbs and woody perennials. However, in plants laccases constitutes a relatively large group of isoenzymes with unique substrate specificities and expression patterns. As part of the strategic research centre Bio4Bio, the present project deals with laccase functions in relation to cell wall formation in grasses based on a study of the model species Brachypodium distachyon. Thirty-one isozymes have been retrieved from the recently published genome. Histochemical assays show high correlation between lignification and laccase-like activity in this species. Temporal and spatial correlation between these processes will be further studied by analysis of gene expression based on quantitative PCR and fluorescent in situ hybridization. Specific isozymes that show high correlation with the process of secondary cell wall formation will be further studied in a reverse genetic study in which candidates will be knocked out using RNA interference. Phenotypes of knock-out mutants are to be described in relation to cell wall degradability in order to reveal possible gains for saccharification of grass-derived feedstocks in bioethanol production and industrial processing.