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
WAP2AQ. The allelic mutation from
q (
WAP2Aq) 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
WAP2Aq and
WAP2D revealed allelic phenotypes against
WAP2AQ, their functions remain to be clarified. We overexpressed full-length cDNAs of
WAP2AQ,
WAP2Aq, and
WAP2D in the
ap2 mutant line of
Arabidopsis.
WAP2AQ fully recovered their flower organs similar to the wild type,
WAP2D showed less recovery, and
WAP2Aq rescued the least mutant flower phenotype. Use of a yeast two-hybrid system showed that
WAP2AQ formed the most homodimers,
WAP2Aq formed the next highest, and
WAP2D formed the least. The sequence comparisons between the three transcription factors and with
AP2 of
Arabidopsis revealed that
WAP2Aq confers two single protein substitutions, I
329-to-V substitution and K
108-to-E in the nuclear translocation signal,
WAP2D harbors SNPs of I
329-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.
View full abstract