A missense mutation in the VHYNP motif of a DELLA protein causes a semi-dwarf mutant phenotype in Brassica napus.
Although dwarf genes have been widely used to improve lodging resistance and enhance harvest index in cereal crops, lodging is still a serious problem in rapeseed (Brassica napus) production. A semi-dwarf B. napus mutant, ds-1, was identified through EMS mutagenesis of a microspore-cultured DH line. The mutant had a significant reduction in height due to a lower first branch position and shorter internodes when compared with wild-type cultivars. This dwarfism was inherited as a single semi-dominant gene, ds-1. DS-1 locus was mapped to chromosome A6, and co-segregated with a microsatellite marker BnEMS1125 derived from the gene BnRGA. BnRGA encodes a DELLA protein that functions as a GA signaling repressor. The expression of a mutant BnRGA allele from ds-1, Bnrga-ds, caused dwarf phenotypes in Arabidopsis. Comparative sequencing of RGA open-reading frames (ORFs) of ds-1 and wild-type cultivars revealed a single proline (P)-to-leucine (L) substitution that may lead to a gain-of-function mutation in GA signaling. The expression of the Arabidopsis homolog, Atrga-ds, bearing this site-directed mutation also rendered dwarf phenotypes in Arabidopsis, which demonstrated that the P-to-L mutation in the VHYNP motif of Bnrga-ds is responsible for the dwarfism. A yeast two-hybrid assay confirmed that this mutation inhibited the interaction between Bnrga-ds/Atrga-ds and the GA receptor, AtGID1A, in the presence of GA(3), suggesting that the conserved proline residue in the VHYNP motif of DELLA protein directly participates in DELLA-GID1 interaction. Identification and characterization of the dwarf gene ds-1 will facilitate its utilization in improving lodging resistance in Brassica breeding.
Liu
Chao
C
National Key Laboratory of Crop Genetic Improvement, National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, China.
Wang
Jilin
J
Huang
Tiandai
T
Wang
Fang
F
Yuan
Fang
F
Cheng
Xiaomao
X
Zhang
Yan
Y
Shi
Shuwen
S
Wu
Jiangsheng
J
Liu
Kede
K
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D029741:Brassica rapa / Q000235:genetics* / Q000254:growth & development*; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense / Q000235:genetics*; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014170:Transformation, Genetic; D020798:Two-Hybrid System Techniques
D005875:Gibberellins; D010940:Plant Proteins; D011956:Receptors, Cell Surface