Dissecting the molecular basis of spike traits by integrating gene regulatory networks and genetic variation in wheat

Spike architecture influences both grain weight and grain number per spike,which are the two major components of grain yield in bread wheat(Triticum aestivum L.).However,the complex wheat genome and the influence of various environmental factors pose challenges in mapping the causal genes that affect spike traits.Here,we systematically identified genes involved in spike trait formation by integrating information on genomic variation and gene regulatory networks controlling young spike development in wheat.We identified 170 loci that are responsible for variations in spike length,spikelet number per spike,and grain number per spike through genome-wide association study and meta-QTL analyses.We constructed gene regulatory networks for young inflorescences at the double ridge stage and thefloret primordium stage,in which the spikelet meristem and thefloret meristem are predominant,respec-tively,by integrating transcriptome,histone modification,chromatin accessibility,eQTL,and protein–pro-tein interactome data.From these networks,we identified 169 hub genes located in 76 of the 170 QTL regions whose polymorphisms are significantly associated with variation in spike traits.The functions of TaZF-B1,VRT-B2,and TaSPL15-A/D in establishment of wheat spike architecture were verified.This study provides valuable molecular resources for understanding spike traits and demonstrates that combining genetic analysis and developmental regulatory networks is a robust approach for dissection of complex traits.

Wide hybridizations reveal the robustness of functional centromeres in Triticum-Aegilops species complex lines

The Triticum-Aegilops complex groups demonstrated high cross-affinity with each other to overcome the barriers of distant hybridization(Loureiro et al.,2023).Distant hybridization involves two distinct yet closely related events:hybridization and genome doubling.Previous studies have indicated that bursts of transposable elements(TEs)can occur as a consequence or concomitant to hybridization or genome duplication(Parisod et al.,2010).This raises an important scientific question regarding how the TEs-rich centromere region copes with genomic shock(McClintock,1984).The Triticum-Aegilops species complexes,particularly in the F1,So,and subsequent early generations resulting from successive selfcrossing,offer an opportunity to investigate whether the centromere environment undergoes reconstruction and the associated mechanisms that maintain genomic stability.

Site-specific transfer of chromosomal segments and genes in wheat engineered chromosomes

Recently, engineered minichromosomes have been produced using a telomere-mediated truncation technique in some plants. However, the study on transferring genes to minichromosomes is very limited.Here, telomere-mediated truncation was successfully performed in common wheat（Triticum aestivum）to generate stable truncated chromosomes accompanied by a relatively high frequency of chromosomal rearrangements. After the cross between transgenic parents, a promoter-less DsRed gene in a chromosome from one parent was transferred to another chromosome from the other parent at the site behind a maize ubiquitin promoter via the Cre/lox system. DsRed transcripts and red fluorescent proteins were detected in the recombinant plants. In one such seedling, transgenic signals were detected at the centric terminus of chromosome 4D and the distal terminus of chromosome 3A. Clear translocations could be detected at the transgenic loci of these two chromosomes. Intriguingly, signals of centric-specific sequences were co-localized with the translocated D-group chromosomal segment in the terminal region of chromosome 3A. Our results indicate that the Cre/lox system induces the gene swapping to the target chromosome and non-homologous chromosomal recombination simultaneously. These approaches could offer a platform to transfer large DNA fragments or even terminal chromosomal segments to other chromosomes of the natural genome.