<i>Key message</i> <p><b>TaGα regulates wheat development in a dose-dependent manner: a single mutant of TaGα solely accelerates heading, while a double mutant not only accelerates heading but also shortens organ length.</b></p> Abstract <p>The Gα subunit plays a crucial role in plant organ development and heading time; however, the exact functions in wheat are unknown. In the present study, knockout mutations in functional <i>TaGα-7A</i> and <i>TaGα-7D</i> were generated in the spring wheat cultivar ‘Fielder’ using the CRISPR/Cas9 system. Both single and double mutants exhibited early heading time. Reduced plant height, leaf length, and grain length were observed exclusively in the double mutant <i>Gα</i>^{<i>Δaadd</i>}, whereas leaf and grain width were unaffected. Histological sections revealed that cell length did not vary between the leaf and stem among ‘Fielder,’ <i>Gα</i>^<i>Δaa</i>, <i>Gα</i>^<i>Δdd</i>, and <i>Gα</i>^{<i>Δaadd</i>}, which indicated that cell number caused the leaf and stem length differences. Transcriptome analysis revealed dysregulated expression of kinesin and tubulin genes in double-mutant leaves, whereas altered oxidoreductase activity and differential expression of flowering-related genes were detected in the leaves of both single and double mutants. Immunoprecipitation coupled with mass spectrometry revealed that glutathione S-transferase (GST) physically interacted with TaGα directly, which was confirmed by luciferase complementation imaging and yeast two-hybrid assay. Furthermore, GST expression and enzyme activity were suppressed in both single and double mutants, resulting in elevated glutathione (GSH) content. The peak GSH content in wheat leaves during development corresponded to the heading time, which implied that GSH may have participated in regulation of heading time. According to the results of the present study, <i>TaGα</i> exerted regulatory effects on plant height, leaf length, grain length, and heading time in a dose-dependent manner via various pathways.</p>