Expression of Flowering Locus C and a frame shift mutation of this gene on chromosome 20 differentiate a summer and winter annual biotype of Camelina sativa

Authors: Anderson, James; Horvath, David; DOGRAMACI, MUNEVVER - Sanford Health; DORN, KEVIN - Kansas State University; Chao, Wun; Watkin, Erin; HERNANDEZ, ALVARO - University Of Illinois; MARKS, DAVID - University Of Minnesota; Gesch, Russell - Russ

Submitted to: Plant Direct
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2018
Publication Date: 7/9/2018
Citation: Anderson, J.V., Horvath, D.P., Dogramaci, M., Dorn, K.M., Chao, W.S., Watkin, E.E., Hernandez, A.G., Marks, M.D., Gesch, R. 2018. Expression of FLOWERING LOCUS C and a frameshift mutation of this gene on chromosome 20 differentiate a summer and winter annual biotype of Camelina sativa. Plant Direct. 2:1-14. https://doi.org/10.1002/pld3.60.
DOI: https://doi.org/10.1002/pld3.60

Interpretive Summary: Camelina [Camelina sativa (L.)] is valued as an industrial oilseed crop and feedstock for production of biofuels and other industrial bio-based products. Cultivars of camelina that flower and mature early are desired in winter cover cropping systems, as it allows for more optimal growing conditions and full development of a late-summer relay- or double-crop. In this study, we confirmed that the camelina cultivar Joelle required a prolonged cold treatment to induce flowering; whereas the cultivar CO46, did not. To gain insights into the flowering habits of these summer- and winter-biotypes at the molecular level, we conducted sequencing of transcripts (RNA) and whole genomes (DNA) from both cultivars. Analysis of the transcript data indicated that one of three copies of a gene, FLOWERING LOCUS C (FLC), known to prevent flowering, was 16-fold greater in Joelle compared to CO46 prior to cold treatment. However, sequencing of this FLC gene identified a one base deletion in CO46 that likely results in a nonfunctional protein, and thus could explain why flowering in CO46 does not require a cold treatment. This information should help in future manipulation of flowering time in new camelina varieties.

Technical Abstract: The nature of the vegetative to reproductive transition in the shoot apical meristem of Camelina sativa summer annual cultivar CO46 and winter annual cultivar Joelle was confirmed by treating seedlings with or without 8 weeks of vernalization. True to their life cycle classification, Joelle required a vernalization treatment to induce bolting and flowering, whereas CO46 did not. In this study, RNAseq, whole genome sequencing, and resequencing of a key floral repressor were used to better understand factors involved in the flowering habit of summer- and winter-biotypes at the molecular level. Analysis of transcriptome data indicated that abundance for one of the three genes encoding the floral repressor FLOWERING LOCUS C (FLC; Csa20g015400) was 16-fold greater in Joelle compared to CO46 prior to vernalization. Abundance of this transcript decreased only slightly in CO46 post-vernalization, compared to a substantial and significant decrease in Joelle. The results observed in the winter annual cultivar Joelle are consistent with repression of FLC by vernalization. However, further characterization of FLC at both the genome and transcriptome levels identified a one base deletion in the 5th exon coding for a keratin-binding domain in chromosome 20 of CO46 and Joelle. The one base deletion detected in chromosome 20 FLC is predicted to result in a frame shift that would produce a non-functional protein. Resequencing of the genome identified the one base deletion in chromosome 20 FLC at a greater ratio in CO46 (2:1) compared to Joelle (1:4); this trend was also observed for transcripts mapping to chromosome 20.