Ectopic expression of maize gene ZmDUF1645 in rice affects rice grain traits and cold tolerance

The DUF protein family is a class of functional proteins containing conserved structural domains that are widely involved in biological processes such as plant seed development, yield formation and response to adversity. Previous research has demonstrated that the heterologous expression of ZmDUF1645 from maize (Zea mays) in rice (Oryza sativa L.) markedly enhances grain yield and influences drought tolerance. However, its effects under other stress conditions remain poorly understood. This study aims to elucidate the role of ZmDUF1645 in rice grain traits and cold tolerance. To this end, the maize gene ZmDUF1645 was expressed in rice, resulting in transgenic plants that exhibited significantly increased yield but reduced grain quality. Further analysis revealed that ZmDUF1645, with functional conservation to its rice homolog OsSGL, exerts pleiotropic effects when ectopically overexpressed in rice. It enhances yield by upregulating GIF1 to promote panicle development, increase grains per panicle, and elevate thousand-grain weight. However, it impairs grain quality (reduced amylose, abnormal starch granules, higher chalkiness) via repressing GBSS1/AGPS2, and compromises cold tolerance by disrupting redox homeostasis, inhibiting superoxide dismutase - SOD; peroxidase - POD; proline - Pro, and downregulating genes related to starch synthesis/energy metabolism. These findings highlight the pleiotropic effects of ZmDUF1645 on rice yield, quality, and stress resistance, offering valuable insights for future crop genetic improvement.