TaPP2C-a6 interacts with TaDOG1Ls and regulates seed dormancy and germination in wheat

Modern wheat cultivation requires seed to germinate rapidly and uniformly with weak dormancy. However, such varieties tend to undergo pre-harvest sprouting (PHS) if the harvest overlaps with the rainy season, causing substantial yield losses. Knowledge regarding the mechanisms of seed dormancy in wheat (Triticum aestivum L.) is limited, with only a few causal genes of the many PHS quantitative trait loci (QTLs) characterized. Here, we emphasize the involvement of ABA signalling core components in regulating seed dormancy and germination in wheat. TaPP2C-a6 was identified as the likely causal gene of wheat PHS-QTLs QPhs.wsu-1A/1B and QPhs1D.1_nwafu loci. Both TaPP2C-a6 and TaPP2C-a7 were highly expressed at embryonic developmental stages and germinating seeds, whereas TaPP2C-a6 was up-regulated during embryo maturation and seed germination. TaPP2C-a6 and TaPP2C-a7 were clade-A PP2Cs that interacted with TaPYLs and class III TaSnRK2s; however, TaPP2C-a6 showed stronger interactions with TaDOG1L members than those of TaPP2C-a7. TaPP2C-a6 overexpression in transgenic Arabidopsis thaliana caused a more severe reduction in ABA sensitivity than TaPP2C-a7 overexpression. Overexpression of TaPP2C-a6 in transgenic A. thaliana and wheat increased PHS levels, whereas TaPP2C-a7 transgenic A. thaliana did not affect PHS levels, confirming that TaPP2C-a6 is a novel regulator of wheat seed dormancy and germination. In summary, we demonstrated that leveraging the knowledge of seed dormancy and germination from model species could rapidly identify the causal genes of PHS-QTLs in wheat. Significantly, we showed that the TaPP2C-TaDOG1L interactions, particularly the interaction strength, could be a new aspect in the regulation of seed dormancy and germination.