A natural tandem array alleviates epigenetic repression of IPA1 and leads to superior yielding rice

Super hybrid rice varieties with ideal plant architecture (IPA) have been critical in enhancing food security worldwide. However, the molecular mechanisms underlying their improved yield remain unclear. Here, we report the identification of a QTL, qWS8/ipa1-2D, in the super rice Yongyou12 (YY12) and related varieties. In-depth genetic molecular characterization of qWS8/ipa1-2D reveals that this newly identified QTL results from three distal naturally occurring tandem repeats upstream of IPA1, a key gene/locus previously shown to shape rice ideal plant architecture and greatly enhance grain yield. The qWS8/ipa1-2D locus is associated with reduced DNA methylation and a more open chromatin state at the IPA1 promoter, thus alleviating the epigenetic repression of IPA1 mediated by nearby heterochromatin. Our findings reveal that IPA traits can be fine-tuned by manipulating IPA1 expression and that an optimal IPA1 expression/dose may lead to an ideal yield, demonstrating a practical approach to efficiently design elite super rice varieties.