A distorted circadian clock causes early flowering and temperature-dependent variation in spike development in the Eps-3Am mutant of einkorn wheat.
Viable circadian clocks help organisms to synchronize their development with daily and seasonal changes, thereby providing both evolutionary fitness and advantage from an agricultural perspective. A high-resolution mapping approach combined with mutant analysis revealed a cereal ortholog of Arabidopsis thaliana LUX ARRHYTHMO/PHYTOCLOCK 1 (LUX/PCL1) as a promising candidate for the earliness per se 3 (Eps-3A(m)) locus in einkorn wheat (Triticum monococcum L.). Using delayed fluorescence measurements it was shown that Eps-3A(m) containing einkorn wheat accession KT3-5 had a distorted circadian clock. The hypothesis was subsequently confirmed by performing a time course study on central and output circadian clock genes, which showed arrhythmic transcript patterns in KT3-5 under constant ambient conditions, i.e., constant light and temperature. It was also demonstrated that variation in spikelet number between wild-type and mutants is sensitive to temperature, becoming negligible at 25°. These observations lead us to propose that the distorted clock is causative for both early flowering and variation in spike size and spikelet number, and that having a dysfunctional LUX could have neutral, or even positive, effects in warmer climates. To test the latter hypothesis we ascertained sequence variation of LUX in a range of wheat germplasm. We observed a higher variation in the LUX sequence among accessions coming from the warmer climate and a unique in-frame mutation in early-flowering Chinese T. turgidum cultivar 'Tsing Hua no. 559.' Our results emphasize the importance of the circadian clock in temperate cereals as a promising target for adaptation to new environments.
Leibniz Institute of Plant Genetics and Crop Plant Research, OT Gatersleben, D-06466 Stadt Seeland, Germany.
Piotr
P
Gawroński
Ruvini
R
Ariyadasa
Axel
A
Himmelbach
Naser
N
Poursarebani
Benjamin
B
Kilian
Nils
N
Stein
Burkhard
B
Steuernagel
Goetz
G
Hensel
Jochen
J
Kumlehn
Sunish Kumar
SK
Sehgal
Bikram S
BS
Gill
Peter
P
Gould
Anthony
A
Hall
Thorsten
T
Schnurbusch
D002874:Chromosome Mapping; D057906:Circadian Clocks; D004252:DNA Mutational Analysis; D035264:Flowers / Q000235:genetics / Q000254:growth & development*; D014644:Genetic Variation; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D013696:Temperature; D014908:Triticum / Q000145:classification / Q000235:genetics / Q000254:growth & development*
D010940:Plant Proteins
circadian clock; earliness per se; flowering time