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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Dairy Forage Research » Research » Publications at this Location » Publication #336571
Title: Transcriptional analysis of flowering time in switchgrass

Author
item TORNQVIST, CARL-ERIK - University Of Wisconsin
item EVANS, JOSEPH - Pioneer Hi-Bred, Inc
item VAILLANCOURT, BRIEANNE - Michigan State University
item KIM, JEONGWOON - Michigan State University
item BUELL, C ROBIN - Michigan State University
item KAEPPLER, SHAWN - University Of Wisconsin
item Casler, Michael

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: Switchgrass is undergoing development as a biomass crop for conversion to bioenergy. Development of switchgrass varieties with extremely late flowering is advantageous because it allows the plant to continue growing and to accumulate biomass throughout the growing season. Finding the major genes that control flowering time would simplify and speed up the breeding process of developing these extremely late flowering varieties. This study identified several key genes in the flowering pathway that showed consistent and significant differential expression between early- and late-flowering switchgrass plants, i.e., different amounts of RNA produced from the gene in early- vs. late-flowering plants. These genes are very similar in sequence to known flowering genes from other grass species. This is the first step toward designing a more efficient system of identifying, selecting, and breeding switchgrass plants that flower late in the growing season after they have accumulated as much biomass as possible from photosynthesis.

Technical Abstract: Over the past two decades, switchgrass (Panicum virgatum) has emerged as a viable biofuel feedstock. The bulk of switchgrass biomass is in the vegetative portion of the plant; a longer vegetative stage leads to an increase in overall biomass yield. The goal of this study was to gain insight into the components of the flowering time pathway in switchgrass and to assist in developing varieties that have extended vegetative phases through delayed flowering. The approach examined differential gene expression between switchgrass genotypes of early- and late-flowering ecotypes. Shoot apical meristem (SAM) and leaf tissue were collected in a developmental series from emergence to anthesis to capture stages of both vegetative and reproductive growth. The morphology of the SAM was also tracked to determine the stage of meristem transition and to choose samples that flanked the SAM transition for sequencing and expression analyses. The analyses revealed differential expression patterns between early- and late-flowering genotypes for known flowering time orthologs, as well as several novel genes, some of which are related to known flowering time genes. In addition, based on expression patterns, many of the identified genes could be classified as putative promoters or repressors of flowering. The candidate genes presented here will be further supported by functional confirmation in switchgrass or the model grass, Brachypodium, and may be used to guide switchgrass improvement through marker-assisted breeding and/or gene transformation methods.