Identification of the Q Gene Playing a Role in Spike Morphology Variation in Wheat Mutants and Its Regulatory Network

Abstract

The wheat AP2 family gene Q controls domestication traits, including spike morphology and threshability, which are critical for the widespread cultivation and yield improvement of wheat. Although many studies have investigated the molecular mechanisms of the Q gene, its direct target genes, especially those controlling spike morphology, are not clear, and its regulatory pathways are not well established. In this study, we conducted gene mapping of a wheat speltoid spike mutant and found that a new allele of the Q gene with protein truncation played a role in spike morphology variation in the mutant. Dynamic expression levels of the Q gene throughout the spike development process suggested that the transcript abundances of the mutant were decreased at the W6 and W7 scales compared to those of the WT. We identified several mutation sites on the Q gene and showed that mutations in different domains resulted in distinct phenotypes. In addition, we found that the Q gene produced three transcripts via alternative splicing and that they exhibited differential expression patterns in nodes, internodes, flag leaves, and spikes. Finally, we identified several target genes directly downstream of Q, including TaGRF1-2D and TaMGD-6B, and proposed a possible regulatory network. This study uncovered the target genes of Q, and the results can help to clarify the mechanism of wheat spike morphology and thereby improve wheat grain yield.

Characterization and Mapping of a Rolling Leaf Mutant Allele rlT73 on Chromosome 1BL of Wheat

“…In the present study, we found that the rlT73 mutant carrying mutation (G581A; Gly194Glu) in the 3' end of miRNA165/166 of HB-B2 showed severe rolling leaf phenotype, paired spikelets comparable to those of rHb-D2 mutants [21,28]. Zhang et al [30] identified several mutation sites on the wheat domestication gene Q and showed that mutations in different domains resulted in distinct phenotypes. Moreover, point mutations interfere with the miRNA172directed cleavage of Q transcripts, which contributes to reduced height/compact spike phenotypes [31] and improved processing quality [32].…”

Identification of a novel SNP in the miR172 binding site ofQhomoeologAP2L-D5is associated with spike compactness and agronomic traits in wheat (Triticum aestivumL.)

“…Greenwood et al (2017) found an increase in rachis node number (which are the nodes that individual spikelets are attached to) with increased AP2L-A5 expression. Conversely, SNS decreased in ap2l5 null mutants generated by Debernardi et al (2020) and in a Q truncation mutant identified by Zhang et al (2022). These results indicate that AP2L5 can delays formation of the terminal spikelet leading to higher SNS.…”

Identification of a novel SNP in the miR172 binding site of Q homoeolog AP2L-D5 is associated with spike compactness and agronomic traits in wheat (Triticum aestivum L.)

“…Greenwood et al ( 2017 ) found an increase in rachis node number (which are the nodes that individual spikelets are attached to) with increased AP2L-A5 expression. Conversely, SNS decreased in ap2l5 null mutants generated by Debernardi et al ( 2020 ) and in a Q truncation mutant identified by Zhang et al ( 2022 ). These results indicate that AP2L5 can delays formation of the terminal spikelet leading to higher SNS.…”