A Single Nucleotide Deletion in Gibberellin20-oxidase1 Causes Alpine Dwarfism in Arabidopsis

Abstract

Alpine dwarfism is widely observed in alpine plant populations and often considered a high-altitude adaptation, yet its molecular basis and ecological relevance remain unclear. In this study, we used map-based cloning and field transplant experiments to investigate dwarfism in natural Arabidopsis (Arabidopsis thaliana) accessions collected from the Swiss Alps. A loss-of-function mutation due to a single nucleotide deletion in gibberellin20-oxidase1 (GA5) was identified as the cause of dwarfism in an alpine accession. The mutated allele, ga5-184, was found in two natural Arabidopsis populations collected from one geographic region at high altitude, but was different from all other reported ga5 null alleles, suggesting that this allele has evolved locally. In field transplant experiments, the dwarf accession with ga5-184 exhibited a fitness pattern consistent with adaptation to high altitude. Across a wider array of accessions from the Swiss Alps, plant height decreased with altitude of origin, but fitness patterns in the transplant experiments were variable and general altitudinal adaptation was not evident. In general, our study provides new insights into molecular basis and possible ecological roles of alpine dwarfism, and demonstrates the importance of the GA-signaling pathway for the generation of ecologically relevant variation in higher plants.

The High Life: Alpine Dwarfism in Arabidopsis

“…They showed, with transplant experiments, that dwarfism indeed appears to be locally adaptive at high altitudes. They found that a mutation in the gene encoding an important enzyme in the GA 3 pathway, GA 20-oxidase (GA5), was responsible for dwarfism (Luo et al, 2015). This particular mutation was common in two geographically proximal high-altitude sites in the Alps and was not found in 855 other Arabidopsis strains sampled from the 1001 Genomes Project (Cao et al, 2011), suggesting that it arose and persisted locally.…”

“…However, like the Green Revolution mutations, the Arabidopsis ga5 mutants cause reduced stature without decreasing yield. This suggests that their spontaneous occurrence may be tolerated; thus, in Switzerland, one allele may have become fortuitously advantageous because it occurred in a population that colonized a high-altitude environment (Luo et al, 2015). This work provides an important inroad to begin understanding the genetic basis of alpine dwarfism and to begin extending this to other species to ask if GA 3 modulation is a common cause of dwarfism in alpine plants.…”

“…A recent study of dwarf stature in alpine colonists of the molecular model Arabidopsis (Arabidopsis thaliana) provides intriguing new hints to the genetic basis of that most ubiquitous of tundra adaptations (Luo et al, 2015). The authors identified dwarf plants common in two high-altitude populations in the Swiss Alps.…”

“…The study by Luo et al (2015) places this potential alpine adaptation firmly in the realm of our knowledge of plant physiology. In agriculture, the Green Revolution of the 1960s and 1970s was facilitated by the development of crop strains with increased grain yield at the expense of biomass production.…”

“…In agriculture, the Green Revolution of the 1960s and 1970s was facilitated by the development of crop strains with increased grain yield at the expense of biomass production. Dwarf plants in wheat (Triticum aestivum) and maize (Zea mays) are defective for a transcription factor that regulates GA 3 signaling (Peng et al, 1999), while the rice (Oryza sativa) Green Revolution dwarfing gene Semidwarf corresponds to the GA 20-oxidase (Spielmeyer et al, 2002), the homolog of the gene affected in the high-altitude Arabidopsis strains (Luo et al, 2015). Mutations in GA5 have been reported to sporadically cause semidwarf stature in Arabidopsis strains worldwide (Barboza et al, 2013), although without obvious association with altitude or other habitat factors.…”