Leaf angle (LA) is a critical agronomic trait in maize, with more upright leaves allowing higher planting density, leading to more efficient light capture and higher yields. A few genes responsible for variation in LA have been identified by map-based cloning. In this study, we cloned maize ZmIBH1-1, which encodes a bHLH transcription factor with both a basic binding region and a helix-loop-helix domain, and the results of qRT-PCR showed that it is a negative regulator of LA. Histological analysis indicated that changes in LA were mainly caused by differential cell wall lignification and cell elongation in the ligular region. To determine the regulatory framework of ZmIBH1-1, we conducted RNA-seq and DNA affinity purification (DAP)-seq analyses. The combined results revealed 59 ZmIBH1-1-modulated target genes with annotations, and they were mainly related to the cell wall, cell development, and hormones. Based on the data, we propose a regulatory model for the control of plant architecture by ZmIBH1-1 in maize.

Background: Appropriate flowering time is very important to the success of modern agriculture. Maize (Zea maysL.) is a major cereal crop, originated in tropical areas, with photoperiod sensitivity. Which is an important obstacle to the utilization of tropical/subtropical germplasm resources in temperate regions. However, the study on the regulation mechanism of photoperiod sensitivity of maize is still in the early stage. Although it has been previously reported thatZmCCTis involved in the photoperiod response and delays maize flowering time under long-day conditions, the underlying mechanism remains unclear.Results: Here, we showed thatZmCCToverexpression delays flowering time and confers maize drought tolerance under LD conditions. Implementing the Gal4-LexA/UAS system identified thatZmCCThas a transcriptional inhibitory activity, while the yeast system showed thatZmCCThas a transcriptional activation activity. DAP-Seq analysis and EMSA indicated thatZmCCTmainly binds to promoters containing the novel motifs CAAAAATC and AAATGGTC. DAP-Seq and RNA-Seq analysis showed thatZmCCTcould directly repress the expression ofZmPRR5andZmCOL9, and promote the expression ofZmRVE6to delay flowering under long-day conditions. Moreover, we also demonstrated thatZmCCTdirectly binds to the promoters ofZmHY5,ZmMPK3,ZmVOZ1andZmARR16and promotes the expression ofZmHY5andZmMPK3, but repressesZmVOZ1andZmARR16to enhance stress resistance. Additionally,ZmCCTregulates a set of genes associated with plant development.Conclusions: ZmCCThas dual functions in regulating maize flowering time and stress response under LD conditions.ZmCCTnegatively regulates flowering time and enhances maize drought tolerance under LD conditions.ZmCCTrepresses most flowering time genes to delay flowering while promotes most stress response genes to enhance stress tolerance. Our data contribute to a comprehensive understanding of the regulatory mechanism ofZmCCTin controlling maize flowering time and stress response.

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.

Summary: The control of flowering time in maize is crucial for reproductive success and yield, and it can be influenced by environmental stresses. Using the approaches of Ac/Ds transposon and transposable element amplicon sequencing techniques, we identified a Ds insertion mutant in the ZmPRR37 gene. The Ds insertion showed a significant correlation with days to anthesis. Further research indicated that ZmPRR37‐CR knockout mutants exhibited early flowering, whereas ZmPRR37‐overexpression lines displayed delayed flowering compared to WT under long‐day (LD) conditions. We demonstrated that ZmPRR37 repressed the expression of ZmNF‐YC2 and ZmNF‐YA3 to delay flowering. Association analysis revealed a significant correlation between flowering time and a SNP2071‐C/T located upstream of ZmPRR37. The SNP2071‐C/T impacted the binding capacity of ZmELF6 to the promoter of ZmPRR37. ZmELF6 also acted as a flowering suppressor in maize under LD conditions. Notably, our study unveiled that ZmPRR37 can enhance salt stress tolerance in maize by directly regulating the expression of ABA‐responsive gene ZmDhn1. ZmDhn1 negatively regulated maize salt stress resistance. In summary, our findings proposed a novel pathway for regulating photoperiodic flowering and responding to salt stress based on ZmPRR37 in maize, providing novel insights into the integration of abiotic stress signals into floral pathways.

Flowering time is an important agronomic trait that determines the distribution and adaptation of plants. The accurate prediction of flowering time in elite germplasm is critical for maize breeding. However, the molecular mechanisms underlying the photoperiod response remain elusive in maize. Here we cloned the flowering time-controlling gene, ZmNF-YC2, by map-based cloning and confirmed that ZmNF-YC2 is the nuclear transcription factor Y subunit C-2 protein and a positive regulator of flowering time in maize under long-day conditions. Our results show that ZmNF-YC2 promotes the expression of ZmNF-YA3. ZmNF-YA3 negatively regulates the transcription of ZmAP2. ZmAP2 suppresses the expression of ZMM4 to delay flowering time. We then developed a gene regulatory model of flowering time in maize using ZmNF-YC2, ZmNF-YA3, ZmAP2, ZMM4, and other key genes. The cascading regulation by ZmNF-YC2 of maize flowering time has not been reported in other species.