INTRODUCTION

Purple wheat (GZ1) is a high-quality wheat variety, and understanding its starch accumulation is key to improving its quality. Investigating how phytohormone regulate starch accumulation during the development of GZ1 grains can shed light on the molecular mechanisms of starch accumulation, supporting optimized wheat production and breeding. This study explored the roles of the phytohormone abscisic acid (ABA) and jasmonic acid (JA) in starch accumulation within purple wheat kernels.

MATERIALS AND METHODS

Wheat variety GZ1 was cultivated under controlled field conditions, with samples collected at 10, 25, and 35 days post-anthesis for RNA extraction, starch and enzyme activity measurements, paraffin sectioning, phytohormone analysis, and qPCR validation.

RESULTS

During grain development at 10, 25, and 35 days post-anthesis (dpa), starch content increased progressively, with the rate of accumulation slowing at 35 dpa. The activities of starch biosynthetic enzymes, including GBSS, SSS, and AGPase, increased from 10 to 25 dpa and declined at 35 dpa. Paraffin section analysis revealed enhanced starch granule accumulation across stages, consistent with the results of starch content measurement. ABA levels showed a continuous increase from 10 to 35 dpa, while both JA and JA-Ile levels decreased from 10 to 25 dpa and then increased markedly at 35 dpa. Venn diagram and heat map analyses showed that at 10 dpa, most ABA-related genes were upregulated, while JA-related genes were predominantly downregulated. By 35 dpa, ABA-related genes exhibited widespread downregulation in number, while JA-related genes showed an almost equal split between up- and downregulation. qRT-PCR results confirmed that the expression trends of ABA- and JA-related genes were consistent with transcriptome data. Starch synthesis-related genes, including TPP-7A, AGPS1a, NAC019, and GBSS1, were upregulated in expression between 10 and 25 dpa and downregulated at 35 dpa. Correlation analysis showed that starch content had a strong positive correlation with ABA levels and the activities of starch biosynthetic enzymes (GBSS, SSS, and AGPase). Starch content exhibited a moderate positive correlation with JA levels and no correlation with JA-Ile levels. ABA levels were positively correlated with the activities of the three starch biosynthetic enzymes, while JA content showed a strong positive correlation only with SSS activity.

CONCLUSION

This study elucidated the time-dependent regulatory roles of ABA and JA in starch accumulation during the natural development of GZ-1 seeds.