Genetic and physical mapping of the earliness per se locus Eps-A (m) 1 in Triticum monococcum identifies EARLY FLOWERING 3 (ELF3) as a candidate gene.

M A Alvarez,N Kippes,J Dubcovsky,G Tranquilli,S Lewis

doi:10.1007/s10142-016-0490-3

Abstract

Wheat cultivars exposed to optimal photoperiod and vernalization treatments still exhibit differences in flowering time, referred to as earliness per se (Eps). We previously identified the Eps-Am1 locus from Triticum monococcum and showed that the allele from cultivated accession DV92 significantly delays heading time and increases the number of spikelets per spike relative to the allele from wild accession G3116. Here, we expanded a high-density genetic and physical map of the Eps-Am1 region and identified the wheat ortholog of circadian clock regulator EARLY FLOWERING 3 (ELF3) as a candidate gene. No differences in ELF3 transcript levels were found between near-isogenic lines carrying the DV92 and G3116 Eps-Am1 alleles, but the encoded ELF3 proteins differed in four amino acids. These differences were associated with altered transcription profiles of PIF-like, PPD1, and FT1, which are known downstream targets of ELF3. Tetraploid wheat lines with combined truncation mutations in the A- and B-genome copies of ELF3 flowered earlier and had less spikelets per spike than the wild-type control under short- and long-day conditions. Both effects were stronger in a photoperiod-sensitive than in a reduced photoperiod-sensitive background, indicating a significant epistatic interaction between PPD1 and ELF3 (P < 0.0001). By contrast, the introgression of the T. monococcum chromosome segment carrying the Eps-Am1 allele from DV92 into durum wheat delayed flowering and increased the number of spikelets per spike. Taken together, the above results support the hypothesis that ELF3 is Eps-Am1. The ELF3 alleles identified here provide additional tools to modulate reproductive development in wheat.Electronic supplementary materialThe online version of this article (doi:10.1007/s10142-016-0490-3) contains supplementary material, which is available to authorized users.

Highlights

More than 700 million tons of wheat is grown every year in very diverse environments, providing a major source of calories and proteins to the human population
We mapped EARLY FLOWERING 3 (ELF3) completely linked to ADK1 inthesameT. monococcum segregating population used before to map earliness per se (Eps)-Am1 (Fig. 1a, Faricelli et al 2010)
near-isogenic lines (NILs) 502 carries the G3116 alleles for MOT1/FTSH4 and the DV92 alleles for ADK1/ELF3 (Fig. 1b), so if this line flowers early it would indicate that Eps-Am1 is linked to MOT1/ FTSH4 and if it flowers late it would indicate that Eps-Am1 is linked to ADK1/ELF3

Summary

Introduction

More than 700 million tons of wheat is grown every year in very diverse environments, providing a major source of calories and proteins to the human population. The ability of wheat to adapt to these different conditions has been favored by a rapidly evolving genome combined with the buffering effect of recent polyploidization events (Dubcovsky and Dvorak 2007) This plasticity, coupled with strong selection pressures during the expansion of agriculture and wheat cultivation throughout the world, contributed to a large genetic diversity in genes regulating reproductive development. This diversity has been used by wheat breeders to optimize the utilization of available natural resources during plant growth and grain filling and to maximize grain yield in different environments. The photoperiod response is mainly regulated by PPD1, a member of the PSEUDO-RESPONSE REGULATOR (PRR) gene

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Conclusion