Comparative Transcript Profiling Suggests Distinct Flowering Response of Early- and Late-Flowering Phenotypes in Forage Grass Dactylis glomerata L

Abstract

Orchardgrass (Dactylis glomerata L.) is an economically important perennial forage grass with a high biomass, abundant carbohydrates, shade tolerance, and broad adaptability. The time of flowering is a crucial agronomic trait that is strongly relevant to the quality and yield of orchardgrass. However, there has been little information provided about the genes expressed during the critical flower development stages. In this study, we performed a comparative transcriptome analysis at different stages in which we compared the early- and late-flowering phenotypes of orchardgrass to identify the regulators and pathways that are involved in timing of flowering. Based on our results, 2561 and 3885 differentially expressed genes (DEGs) were identified between the late- and early-flowering phenotypes of orchardgrass in vernalization stage (VE) and before heading (BH) stages, respectively. Gene ontology analysis indicated that the DEGs in VE stage were primarily related to plant hormones, development processes, and environmental stimulation in response to vernalization induction. At the BH stage, DEGs were related to plant development processes and organ formation and differentiation. A large number of heat shock factors (HSFs) were detected in cooperation with plant hormone regulators in the heading (HT) stage. Ultimately, 50 flowering genes discovered were studied as DEGs between different phenotypes in flowering time, and 25 of those flowering DEGs were involved in the photoperiod pathway. These 50 DEGs revealed gene transcripts that corresponded to flowering-associated differences, and they provide novel insights into the molecular mechanisms that underlie regulation of flowering in early-flowering and late-flowering phenotypes of orchardgrass.