Molecular characterization of Rht-1 dwarfing genes in hexaploid wheat.

Abstract

The introduction of the Reduced height (Rht)-B1b and Rht-D1b semidwarfing genes led to impressive increases in wheat (Triticum aestivum) yields during the Green Revolution. The reduction in stem elongation in varieties containing these alleles is caused by a limited response to the phytohormone gibberellin (GA), resulting in improved resistance to stem lodging and yield benefits through an increase in grain number. Rht-B1 and Rht-D1 encode DELLA proteins, which act to repress GA-responsive growth, and their mutant alleles Rht-B1b and Rht-D1b are thought to confer dwarfism by producing more active forms of these growth repressors. While no semidwarfing alleles of Rht-A1 have been identified, we show that this gene is expressed at comparable levels to the other homeologs and represents a potential target for producing novel dwarfing alleles. In this study, we have characterized additional dwarfing mutations in Rht-B1 and Rht-D1. We show that the severe dwarfism conferred by Rht-B1c is caused by an intragenic insertion, which results in an in-frame 90-bp insertion in the transcript and a predicted 30-amino acid insertion within the highly conserved amino-terminal DELLA domain. In contrast, the extreme dwarfism of Rht-D1c is due to overexpression of the semidwarfing Rht-D1b allele, caused by an increase in gene copy number. We show also that the semidwarfing alleles Rht-B1d and Rht-B1e introduce premature stop codons within the amino-terminal coding region. Yeast two-hybrid assays indicate that these newly characterized mutations in Rht-B1 and Rht-D1 confer "GA-insensitive" dwarfism by producing DELLA proteins that do not bind the GA receptor GA INSENSITIVE DWARF1, potentially compromising their targeted degradation.

• Authors: Stephen Pearce, Robert Saville, Simon P Vaughan, Peter M Chandler, Edward P Wilhelm, Caroline A Sparks, Nadia Al-Kaff, Andrey Korolev, Margaret I Boulton, Andrew L Phillips, Peter Hedden, Paul Nicholson, Stephen G Thomas
• Journal: Plant physiology (Plant Physiol) Vol. 157 Issue 4 Pg. 1820-31 (Dec 2011) ISSN: 1532-2548 [Electronic] United States
• PMID: 22013218 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• DNA, Plant
• Gibberellins
• Plant Growth Regulators
• Plant Proteins
• RHT-D1A protein, Triticum aestivum
• RNA, Messenger
• RNA, Plant

Topics

• Alleles
• Amino Acid Sequence
• Base Sequence
• DNA, Plant (chemistry, genetics)
• Gibberellins (pharmacology)
• Molecular Sequence Data
• Mutation
• Phenotype
• Plant Growth Regulators (pharmacology)
• Plant Proteins (genetics, metabolism)
• Plant Stems (genetics, growth & development)
• Polyploidy
• RNA, Messenger (genetics)
• RNA, Plant (genetics)
• Sequence Alignment
• Sequence Analysis, DNA
• Triticum (genetics, growth & development, metabolism)
• Two-Hybrid System Techniques