The GZnC1 variant from common wild rice influences grain Zn content

Zinc (Zn) deficiency, caused by inadequate Zn intake in the human diet, has serious health implications. Rice (Oryza sativa) is the staple food in regions with a high incidence of Zn deficiency, so raising Zn levels in rice grain could help alleviate Zn deficiency. The wild relatives of cultivated rice vary widely in grain Zn content and thus are suitable resources for improving this trait. However, few loci underlying grain Zn content have been identified in wild rice relatives. Here, we identified a major quantitative trait locus for grain Zn content, Grain Zn Content 1 (qGZnC1), from Yuanjiang common wild rice (Oryza rufipogon Griff.) using map-based cloning. Down-regulating GZnC1 expression reduced the grain Zn content, whereas the presence of GZnC1 had the opposite effect, indicating that GZnC1 is involved in grain Zn content in rice. Notably, GZnC1 is identical to a previously reported gene, EMBRYO SAC ABORTION 1 (ESA1), involved in seed setting rate. The mutation in GZnC1/ESA1 at position 1819 (^T1819^C) causes delayed termination of protein translation. In addition, GZnC1 is specifically expressed in developing panicles. Several genes related to Zn-transporter genes were up-regulated in the presence of GZnC1. Our results suggest that GZnC1 activates Zn transporters to promote Zn distribution in panicles. Our work thus sheds light on the genetic mechanism of Zn accumulation in rice grain and provides a new genetic resource for improving Zn content in rice.