A single amino acid change led to structural and functional differentiation of PvHd1 to control flowering in switchgrass

Abstract

Switchgrass, a forage and bioenergy crop, occurs as two main ecotypes with different but overlapping ranges of adaptation. The two ecotypes differ in a range of characteristics, including flowering time. Flowering time determines the duration of vegetative development and therefore biomass accumulation, a key trait in bioenergy crops. No causal variants for flowering time differences between switchgrass ecotypes have, as yet, been identified. In this study, we mapped a robust flowering time quantitative trait locus (QTL) on chromosome 4K in a biparental F2 population and characterized the flowering-associated transcription factor PvHd1, an ortholog of CONSTANS in Arabidopsis and Heading date 1 in rice, as the underlying causal gene. Protein modeling predicted that a serine to glycine substitution at position 35 (p.S35G) in B-Box domain 1 greatly altered the global structure of the PvHd1 protein. The predicted variation in protein compactness was supported in vitro by a 4ºC-shift in denaturation temperature. Overexpressing the PvHd1-p.35S allele in a late-flowering CONSTANS-null Arabidopsis mutant rescued earlier flowering, whereas PvHd1-p.35G had a reduced ability to promote flowering, demonstrating that the structural variation led to functional divergence. Our findings provide us with a tool to manipulate the timing of floral transition in switchgrass cultivars and, potentially, expand their cultivation range.

Advances in Molecular Breeding of Forage Crops: Technologies, Applications and Prospects

“…Furthermore, the timing of flowering, a critical factor in biomass accumulation, has been thoroughly investigated. Choi et al (2023) pinpointed a QTL affecting flowering time in switchgrass [13], whereas Jiang et al (2022) identified several QTLs that control this trait in alfalfa [14]. These groundbreaking discoveries provide essential insights that are crucial in developing breeding strategies aimed at optimizing biomass production.…”

Finger millet: a hero in the making to combat food insecurity

“…This approach removes a lot of the genotypic variation that is not associated with the trait of interest, similarly to a bulked segregant approach, but requires that the genes and alleles that confer Al tolerance are the same across accessions within a pseudoreplicate. Pseudoreplication has previously been successfully used in the identification of candidate genes for flowering time and wax deposition in switchgrass (Choi et al 2023 ; Qi et al 2021 ). Another consideration in RNA-seq analyses of allopolyploids is the possible co-alignment of reads from more than one subgenome.…”

Diversity of Heading date 1 (Hd1) gene that conditioning flowering time in traditional tropical japonica and traditional indica rice from Thailand

“…These genetic variations can alter the stability and function of transcripts and protein function of this gene. For example, an amino acid change of PvHd1 gene in switchgrass lead to structural and functional differentiation(Choi et al 2023). Traditional rice cultivars grown in different natural agroecosystem in Thailand exhibited Hd1 gene variations between northern (upland rice) and northeastern (lowland rice) re ect to variation of mode of adaptation to different local environments (i.e., light and temperature).…”