ZmILI1 regulates leaf angle by directly affecting liguleless1 expression in maize

Abstract

The leaf angle in a plant canopy has a significant impact on the reflectance, transmittance and absorption of solar light in maize. Plants with upright leaves can be planted closer together, thereby increasing yield/unit area. To identify genetic components of leaf angle important for yield gain, we took advantage of a set of near-isogenic line population developed from erect and expanded inbred lines. Fine mapping of a major effect QTL qLA2 on chromosome 2 for leaf angle led to the identification of ZmILI1, a functional orthologue of ILI1 in rice. The zmili1 mutants showed reduced leaf angle phenotype. DAP-Seq analysis and expression of target genes showed that ZmILI1 not only directly affected genes associated with auxin polar transport, BR signaling pathway, response to cytokinin and cell differentiation genes, but it also affected auxin and BR biosynthetic process genes regulating leaf angle. Especially, ZmILI1 directly bound to the promoter of the downstream gene LIGULELESS1 (LG1) and activated LG1 to increase leaf angle. We also found that ZmILI1 and CYP90D1formed a new negative feedback loop to maintain the balance of Brassinolide in maize. These results provide useful information for the elucidation of the molecular mechanisms underlying leaf angle formation in maize.