Overexpression of Q/q-related homoeoalleles of hexaploid wheat reveals distinct recovery of flower transformation in the apetala2 mutant of Arabidopsis

抄録

The Q gene has played substantial roles in wheat domestication. As it pleiotropically governs domestication-related traits, such as free threshing, glume shape and tenacity, rachis fragility, spike length, plant height, and flowering time, wheat is cultivated in widespread adaptation. The Q gene located on the A genome encodes the APETALA2-like transcription factor WAP2A^Q. The allelic mutation from q (WAP2A^q) to Q took place in the polyploidy wheats, and the B and D genomes of bread (hexaploid) wheat conferred its homoeoalleles (WAP2B and WAP2D, respectively). Although WAP2A^q and WAP2D revealed allelic phenotypes against WAP2A^Q, their functions remain to be clarified. We overexpressed full-length cDNAs of WAP2A^Q, WAP2A^q, and WAP2D in the ap2 mutant line of Arabidopsis. WAP2A^Q fully recovered their flower organs similar to the wild type, WAP2D showed less recovery, and WAP2A^q rescued the least mutant flower phenotype. Use of a yeast two-hybrid system showed that WAP2A^Q formed the most homodimers, WAP2A^q formed the next highest, and WAP2D formed the least. The sequence comparisons between the three transcription factors and with AP2 of Arabidopsis revealed that WAP2A^q confers two single protein substitutions, I₃₂₉-to-V substitution and K₁₀₈-to-E in the nuclear translocation signal, WAP2D harbors SNPs of I₃₂₉-to-L similar to Arabidopsis, and other 6 substitutions. These data support the idea that a critical point mutation at the functional domain and structure alteration(s) resulting from sequence diversifications caused functional differences in the genes. Mutant lines of Arabidopsis can become a powerful tool for analyzing foreign gene functions as in the case of wheat.