Sequence variations of the partially dominant DELLA gene Rht-B1c in wheat and their functional impacts

Abstract

Rht-B1c, allelic to the DELLA protein-encoding gene Rht-B1a, is a natural mutation documented in common wheat (Triticum aestivum). It confers variation to a number of traits related to cell and plant morphology, seed dormancy, and photosynthesis. The present study was conducted to examine the sequence variations of Rht-B1c and their functional impacts. The results showed that Rht-B1c was partially dominant or co-dominant for plant height, and exhibited an increased dwarfing effect. At the sequence level, Rht-B1c differed from Rht-B1a by one 2kb Veju retrotransposon insertion, three coding region single nucleotide polymorphisms (SNPs), one 197bp insertion, and four SNPs in the 1kb upstream sequence. Haplotype investigations, association analyses, transient expression assays, and expression profiling showed that the Veju insertion was primarily responsible for the extreme dwarfing effect. It was found that the Veju insertion changed processing of the Rht-B1c transcripts and resulted in DELLA motif primary structure disruption. Expression assays showed that Rht-B1c caused reduction of total Rht-1 transcript levels, and up-regulation of GATA-like transcription factors and genes positively regulated by these factors, suggesting that one way in which Rht-1 proteins affect plant growth and development is through GATA-like transcription factor regulation.

Changes in Water Status, Membrane Stability and Antioxidant Capacity of Wheat Seedlings Carrying Different Rht‐B1 Dwarfing Alleles under Drought Stress

“…, Wen et al. ). Thus, the wheat GA‐insensitive DELLA mutations Rht‐B1c and Rht‐B1b produce dwarf and semidwarf phenotypes, respectively, by DELLAs‐mediated growth inhibition.…”

“…The allele Rht-B1b contains single nucleotide substitutions that introduce premature stop codons in the N-terminal coding region and result in truncated proteins (Peng et al 1999). The Rht-B1c allele represents an intragenic insertion in the N-terminal domain and two SNPs (single nucleotide polymorphisms), manifested by a 30-amino acid insertion and two-amino acid substitutions in the resulting proteins, respectively (Pearce et al 2011, Wen et al 2013. Thus, the wheat GA-insensitive DELLA mutations Rht-B1c and Rht-B1b produce dwarf and semidwarf phenotypes, respectively, by DELLAs-mediated growth inhibition.…”

“…, Wen et al. ). It was suggested that both mutant DELLAs are unable to interact with the GA receptor, GID1 (GA‐INSENSITIVE DWARF1), resulting in reduced GA responsiveness even at adequate hormone levels.…”

“…In wheat, DEL-LAs are encoded by the wild alleles of the reduced height (Rht) genes, well known for their impact in the 'Green Revolution' wheat cultivars. The alleles Rht-B1b (=Rht1) and Rht-B1c (=Rht3) are mutations within the N-terminal DELLA domain resulting in altered DELLA proteins (Peng et al 1999, Pearce et al 2011, Wen et al 2013. It was suggested that both mutant DELLAs are unable to interact with the GA receptor, GID1 (GA-INSENSITIVE DWARF1), resulting in reduced GA responsiveness even at adequate hormone levels.…”

Molecular background of cadmium tolerance in Rht dwarf wheat mutant is related to a metabolic shift from proline and polyamine to phytochelatin synthesis

“…The wild allele -B1a at locus Rht-B1 encodes for DELLA proteins, which act as transcriptional repressors of the GA signalling pathway and retard plant growth (Achard and Genschik 2009). The mutant allele -B1c at the same locus (formerly designated as the Rht3 gene) encodes for aberrant DELLA proteins that are unable to interact with the GA receptor, resulting in reduced GA responsiveness (Wen et al 2013). The better stress tolerance of the Rht-B1c line has been related to alterations of the photosynthetic membranes, the increased capacity of the photosystem I cyclic electron transport, the accumulation of osmoprotectants and the higher activity of certain antioxidant enzymes (Dobrikova et al 2017).…”