Summary: The AGAMOUS‐LIKE6 (AGL6)‐like genes are ancient MADS‐box genes and are functionally studied in a few model plants. The knowledge of these genes in wheat remains limited. Here, by studying a ‘double homoeolog mutant’ of the AGL6 gene in tetraploid wheat, we showed that AGL6 was required for the development of all four whorls of floral organs with dosage‐dependent effect on floret fertility. Yeast two‐hybrid analyses detected interactions of AGL6 with all classes of MADS‐box proteins in the ABCDE model for floral organ development. AGL6 was found to interact with several additional proteins, including the G protein β and γ (DEP1) subunits. Analysis of the DEP1‐B mutant showed a significant reduction in spikelet number per spike in tetraploid wheat, while overexpression of AGL6 in common wheat increased the spikelet number per spike and hence the grain number per spike. RNA‐seq analysis identified the regulation of several meristem activity genes by AGL6, such as FUL2 and TaMADS55. Our work therefore extensively updated the wheat ABCDE model and proposed an alternative approach to improve wheat grain yield by manipulating the AGL6 gene.

Summary: Grain size and filling are two key determinants of grain thousand‐kernel weight (TKW) and crop yield, therefore they have undergone strong selection since cereal was domesticated. Genetic dissection of the two traits will improve yield potential in crops. A quantitative trait locus significantly associated with wheat grain TKW was detected on chromosome 7AS flanked by a simple sequence repeat marker of Wmc17 in Chinese wheat 262 mini‐core collection by genome‐wide association study. Combined with the bulked segregant RNA‐sequencing (BSR‐seq) analysis of an F₂ genetic segregation population with extremely different TKW traits, a candidate trehalose‐6‐phosphate phosphatase gene located at 135.0 Mb (CS V1.0), designated as TaTPP‐7A, was identified. This gene was specifically expressed in developing grains and strongly influenced grain filling and size. Overexpression (OE) of TaTPP‐7A in wheat enhanced grain TKW and wheat yield greatly. Detailed analysis revealed that OE of TaTPP‐7A significantly increased the expression levels of starch synthesis‐ and senescence‐related genes involved in abscisic acid (ABA) and ethylene pathways. Moreover, most of the sucrose metabolism and starch regulation‐related genes were potentially regulated by SnRK1. In addition, TaTPP‐7A is a crucial domestication‐ and breeding‐targeted gene and it feedback regulates sucrose lysis, flux, and utilization in the grain endosperm mainly through the T6P‐SnRK1 pathway and sugar–ABA interaction. Thus, we confirmed the T6P signalling pathway as the central regulatory system for sucrose allocation and source–sink interactions in wheat grains and propose that the trehalose pathway components have great potential to increase yields in cereal crops.

Summary: Plant breeding is constrained by trade‐offs among different agronomic traits by the pleiotropic nature of many genes. Genes that contribute to two or more favourable traits with no penalty on yield are rarely reported, especially in wheat. Here, we describe the editing of a wheat auxin response factor TaARF12 by using CRISPR/Cas9 that rendered shorter plant height with larger spikes. Changes in plant architecture enhanced grain number per spike up to 14.7% with significantly higher thousand‐grain weight and up to 11.1% of yield increase under field trials. Weighted Gene Co‐Expression Network Analysis (WGCNA) of spatial–temporal transcriptome profiles revealed two hub genes: RhtL1, a DELLA domain‐free Rht‐1 paralog, which was up‐regulated in peduncle, and TaNGR5, an organ size regulator that was up‐regulated in rachis, in taarf12 plants. The up‐regulation of RhtL1 in peduncle suggested the repression of GA signalling, whereas up‐regulation of TaNGR5 in spike may promote GA response, a working model supported by differential expression patterns of GA biogenesis genes in the two tissues. Thus, TaARF12 complemented plant height reduction with larger spikes that gave higher grain yield. Manipulation of TaARF12 may represent a new strategy in trait pyramiding for yield improvement in wheat.

Summary: Upland cotton (Gossypium hirsutum) is the world's largest source of natural fibre and dominates the global textile industry. Hybrid cotton varieties exhibit strong heterosis that confers high fibre yields, yet the genome‐wide effects of artificial selection that have influenced Upland cotton during its breeding history are poorly understood. Here, we resequenced Upland cotton genomes and constructed a variation map of an intact breeding pedigree comprising seven elite and 19 backbone parents. Compared to wild accessions, the 26 pedigree accessions underwent strong artificial selection during domestication that has resulted in reduced genetic diversity but stronger linkage disequilibrium and higher extents of selective sweeps. In contrast to the backbone parents, the elite parents have acquired significantly improved agronomic traits, with an especially pronounced increase in the lint percentage. Notably, identify by descent (IBD) tracking revealed that the elite parents inherited abundant beneficial trait segments and loci from the backbone parents and our combined analyses led to the identification of a core genomic segment which was inherited in the elite lines from the parents Zhong 7263 and Ejing 1 and that was strongly associated with lint percentage. Additionally, SNP correlation analysis of this core segment showed that a non‐synonymous SNP (A‐to‐G) site in a gene encoding the cell wall‐associated receptor‐like kinase 3 (GhWAKL3) protein was highly correlated with increased lint percentage. Our results substantially increase the valuable genomics resources available for future genetic and functional genomics studies of cotton and reveal insights that will facilitate yield increases in the molecular breeding of cotton.

Terpenes are the largest and most diverse class of secondary metabolites in plants and play a very important role in plant adaptation to environment. 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is a rate-limiting enzyme in the process of terpene biosynthesis in the cytosol. Previous study found the HMGR genes underwent gene expansion in Gossypium raimondii, but the characteristics and evolution of the HMGR gene family in Gossypium genus are unclear. In this study, genome-wide identification and comparative study of HMGR gene family were carried out in three Gossypium species with genome sequences, i.e., G. raimondii, Gossypium arboreum, and Gossypium hirsutum. In total, nine, nine and 18 HMGR genes were identified in G. raimondii, G. arboreum, and G. hirsutum, respectively. The results indicated that the HMGR genes underwent gene expansion and a unique gene cluster containing four HMGR genes was found in all the three Gossypium species. The phylogenetic analysis suggested that the expansion of HMGR genes had occurred in their common ancestor. There was a pseudogene that had a 10-bp deletion resulting in a frameshift mutation and could not be translated into functional proteins in G. arboreum and the A-subgenome of G. hirsutum. The expression profiles of the two pseudogenes showed that they had tissue-specific expression. Additionally, the expression pattern of the pseudogene in the A-subgenome of G. hirsutum was similar to its paralogous gene in the D-subgenome of G. hirsutum. Our results provide useful information for understanding cytosolic terpene biosynthesis in Gossypium species.