TaZIM-A1 negatively regulates flowering time in common wheat (Triticum aestivum L.)

Flowering time is a critical determinant of regional adaptation for crops and has strong effects on crop yields. Here, we report that TaZIM-A1, an atypical GATA-like transcription factor, is a negative regulator of flowering in wheat. TaZIM-A1 possessed weak transcriptional repression activity, with its CCT domain functioning as the major inhibitory region. TaZIM-A1 expression exhibited a typical circadian oscillation pattern under various light regimes. Overexpression of TaZIM-A1 caused a delay in flowering time and a decrease in thousand-kernel weight (TKW) in wheat under long-day conditions. Moreover, TaZIM-A1 directly bound to the promoters of TaCO-1 and TaFT-1 and downregulated their expression. Sequence analysis of a collection of common wheat cultivars identified three and two haplotypes for TaZIM-A1 and TaZIM-B1, respectively. Association analysis revealed that TaZIM-A1-HapI/-HapIII and TaZIM-B1-HapI have undergone strong positive selection during modern wheat breeding, likely due to their association with earlier heading and higher TKW. Diagnostic markers were developed for these haplotypes that can be used for wheat cultivar improvement, via marker-assisted breeding.