Meristems contain groups of indeterminate stem cells, which are maintained by a feedback loop between CLAVATA (CLV) and WUSCHEL (WUS) signaling. CLV signaling involves the secretion of the CLV3 peptide and its perception by a number of Leucine-Rich-Repeat (LRR) receptors, including the receptor-like kinase CLV1 and the receptor-like protein CLV2 coupled with the CORYNE (CRN) pseudokinase. CLV2, and its maize ortholog FASCIATED EAR2 (FEA2) appear to function in signaling by CLV3 and several related CLV3/EMBRYO-SURROUNDING REGION (CLE) peptide ligands. Nevertheless, how signaling specificity is achieved remains unknown. Here we show that FEA2 transmits signaling from two distinct CLE peptides, the maize CLV3 ortholog ZmCLE7 and ZmFON2-LIKE CLE PROTEIN1 (ZmFCP1) through two different candidate downstream effectors, the alpha subunit of the maize heterotrimeric G protein COMPACT PLANT2 (CT2), and ZmCRN. Our data provide a novel framework to understand how diverse signaling peptides can activate different downstream pathways through common receptor proteins.

Maize ear size and kernel number differ among lines, however, little is known about the molecular basis of ear length and its impact on kernel number. Here, we characterize a quantitative trait locus, qEL7, to identify a maize gene controlling ear length, flower number and fertility. qEL7 encodes 1-aminocyclopropane-1- carboxylate oxidase2 (ACO2), a gene that functions in the final step of ethylene biosynthesis and is expressed in specific domains in developing inflorescences. Confirmation of qEL7 by gene editing of ZmACO2 leads to a reduction in ethylene production in developing ears, and promotes meristem and flower development, resulting in a ~13.4% increase in grain yield per ear in hybrids lines. Our findings suggest that ethylene serves as a key signal in inflorescence development, affecting spikelet number, floral fertility, ear length and kernel number, and also provide a tool to improve grain productivity by optimizing ethylene levels in maize or in other cereals.

Summary: Multiple distinct specialized regions shape the architecture of maize leaves. Among them, the fringe‐like and wedge‐shaped auricles alter the angle between the leaf and stalk, which is a key trait in crop plant architecture. As planting density increased, a small leaf angle (LA) was typically selected to promote crop light capture efficiency and yield. In the present study, we characterized two paralogous INDETERMINATE DOMAIN (IDD) genes, ZmIDD14 and ZmIDD15, which contain the Cys2‐His2 zinc finger domain and function redundantly to regulate auricle development and LA in maize. Loss‐of‐function mutants showed decreased LA by reducing adaxial sclerenchyma thickness and increasing the colourless cell layers. In addition, the idd14;idd15 double mutant exhibited asymmetrically smaller auricles, which might cause by a failed maintenance of symmetric expression of the key auricle size controlling gene, LIGULELESS(LG1). The transcripts of ZmIDD14 and ZmIDD15 enriched in the ligular region, where LG1 was highly expressed, and both proteins physically interacted with ZmILI1 to promote LG1 transcription. Notably, the idd14;idd15 enhanced the grain yield of hybrids under high planting densities by shaping the plant architecture with a smaller LA. These findings demonstrate the functions of ZmIDD14 and ZmIDD15 in controlling the abaxial/adaxial development of sclerenchyma in the midrib and polar development along the medial‐lateral axes of auricles and provide an available tool for high‐density and high‐yield breeding in maize.

Summary: Kernel row number (KRN) is a major yield related trait for maize (Zea mays L.) and is also a major goal of breeders, as it can increase the number of kernels per plant. Thus, identifying new genetic factors involving in KRN formation may accelerate improving yield‐related traits genetically. We herein describe a new kernel number‐related gene (KRN5b) identified from KRN QTL qKRN5b and encoding an inositol polyphosphate 5‐phosphatase (5PTase). KRN5b has phosphatase activity towards PI(4,5)P₂, PI(3,4,5)P₃, and Ins(1,4,5)P₃ in vitro. Knocking out KRN5b caused accumulation of PI(4,5)P₂ and Ins(1,4,5)P₃, resulting in disordered kernel rows and a decrease in the number of kernels and tassel branches. The introgression of the allele with higher expression abundance into different inbred lines could increase the ear weight of the inbred lines and the corresponding hybrids by 10.1%–12.2% via increasing KRN, with no adverse effects on other agronomic traits. Further analyses showed that KRN5b regulates inflorescence development through affecting the synthesis and distribution of hormones. Together, KRN5b contributes to spikelet pair meristem development through inositol phosphate and phosphatidylinositols, making it a selecting target for yield improvement.