Maize transcription factor ZmHY5L shapes waxy gene starch quality and grain size

Researchers working with two characteristic waxy maize landraces from Yunnan have identified a transcription factor that directly controls the expression of the waxy gene, a key determinant of grain quality in maize. The factor, named ZmHY5L, belongs to the basic leucine zipper (bZIP) family and is one of the homologous genes of the Arabidopsis light-signaling regulator HY5. According to the study, published in Theoretical and Applied Genetics, ZmHY5L positively regulates waxy transcription by specifically binding to G-box elements in the gene’s promoter, and in doing so simultaneously influences both starch quality and grain morphology in the maize endosperm.

To find candidate regulators, the team used DNA pull-down combined with mass spectrometry, and this screen pointed to ZmHY5L as an upstream regulatory factor of the waxy gene.

The researchers then verified the interaction with a series of standard molecular tests. Subcellular localization confirmed that the ZmHY5L protein resides in the nucleus, as expected for a transcription factor. Electrophoretic mobility shift assays and yeast one-hybrid assays both confirmed a direct interaction between ZmHY5L and the regulatory region of the waxy gene.

The functional consequences became clear when the team constructed ZmHY5L gene-editing mutants and compared their phenotypes with normal plants. In the mutants, the GBSSI protein content in maize kernels was significantly reduced, consistent with the loss of a positive transcriptional activator acting on the gene that encodes that enzyme.

Reduced GBSSI shifted the composition of the starch itself. At the same time, the edited plants produced grains with larger volume and higher hundred-grain weight, meaning the transcription factor’s influence extends beyond starch chemistry into the physical morphology of the grain.

Notably, these shifts occurred without altering the total starch content of the kernels, indicating that ZmHY5L reshapes the balance between amylose and amylopectin and the architecture of the grain rather than the overall amount of starch deposited.

Taken together, the findings establish ZmHY5L as a G-box-binding transcriptional activator of the maize waxy gene with pleiotropic effects on endosperm starch quality and grain morphology. Because the study was conducted in two Yunnan waxy landraces using gene-editing mutants for phenotype comparison, the results are rooted in a specific genetic background, but they provide a mechanistic entry point for understanding how a light-signaling-associated factor tunes amylose synthesis and grain traits in maize.

Subject of Research: Transcriptional regulation of the maize waxy gene by the bZIP factor ZmHY5L and its effects on endosperm starch quality and grain morphology

Article Title: ZmHY5L synergistically affects endosperm starch quality and grain morphology through G-box-mediated transcriptional regulation of the maize waxy gene

Article References: Du, J., Ye, Y., Chen, X., Li, F., Yin, G., & Wu, X. (2026). ZmHY5L synergistically affects endosperm starch quality and grain morphology through G-box-mediated transcriptional regulation of the maize waxy gene. Theoretical and Applied Genetics, 139(11), Article 312. https://doi.org/10.1007/s00122-026-05425-0

Image Credits: AI Generated

DOI: 10.1007/s00122-026-05425-0

Keywords: maize, waxy gene, ZmHY5L, GBSSI, amylose, starch quality, grain morphology, transcription factor, G-box, gene editing, waxy maize landraces, Yunnan