Fructan biosynthesis gene expression upon cold acclimation in orchardgrass (Dactylis glomerata L.)

Authors: Bushman, Bradley; Robins, Joseph; ZHAO, XINXIN - Chengdu University; FENG, GUANGYAN - Sichuan Agricultural University; ZHANG, XINQUAN - Sichuan Agricultural University; HUANG, LINKAI - Sichuan Agricultural University; Robbins, Matthew

Submitted to: Grassland Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2025
Publication Date: 6/20/2025
Citation: Bushman, B.S., Robins, J.G., Zhao, X., Feng, G., Zhang, X., Huang, L., Robbins, M.D. 2025. Fructan biosynthesis gene expression upon cold acclimation in orchardgrass (Dactylis glomerata L.). Grassland Research. 4(2):121-130. https://doi.org/10.1002/glr2.70011.
DOI: https://doi.org/10.1002/glr2.70011

Interpretive Summary: Fructan content and flux in temperate forages can benefit the grasses through increased cold hardiness, increased drought tolerance, and improved forage quality. Orchardgrass (Dactylis glomerata L.) produces a straightforward series of fructans, and would be an ideal genetic model for fructan biosynthesis, but the genes involved in their biosynthesis are uncharacterized because of its polyploidy and complex genome. Recently a reference genome of orchardgrass was published, and we use that as a source of fructan biosynthesis genes to survey expression in diverse orchardgrass germplasm. We found the candidate for sucrose:fructan 6-fructosyltransferase (6-SFT), which had the highest transcript levels of any related gene in this study and was induced upon cold acclimation. We also found that for each main gene family, there was one gene with high expression and no mutations in major motifs while the related genes had low expression and evidence of mutations. These data provide putative roles of fructan biosynthesis genes, and show which genes play a role in fructan biosynthesis for cold acclimation in orchardgrass.

Technical Abstract: Fructan content and flux in temperate forages can benefit the grasses through increased cold hardiness, increased drought tolerance, and improved forage quality. Orchardgrass (Dactylis glomerata L.) produces relatively long and unbranched levan-type fructans, but the genes involved in their biosynthesis are uncharacterized. Through the evaluation of five orchardgrass cultivars and breeding lines that differ in their cold hardiness and freezing tolerance, we show that their fructan accumulation upon cold acclimation was similar. The glycoside hydrolase-32 (GH32) gene family members involved in fructan biosynthesis were identified and grouped with homologous genes from Triticum aestivum and Lolium perenne. In each of four sub-clades of the GH32 gene family, there were specific genes with high transcript levels and no deletions in GH32 motifs. The candidate for sucrose:fructan 6-fructosyltransferase (6-SFT) exhibited the highest transcript levels of any GH32 gene in this study and was induced upon cold acclimation. Conversely, three invertase and two fructan exohydrolase genes, with roles in sucrose and fructan hydrolysis, had reduced transcript levels upon cold acclimation. These data provide putative roles of GH32 genes, and show which genes play a role in fructan biosynthesis for cold acclimation in orchardgrass.