Grain yield in bread wheat (Triticum aestivum L.) is largely determined by inflorescence architecture. Zang734 is an endemic Tibetan wheat variety that exhibits a rare triple spikelet (TRS) phenotype with significantly increased spikelet/floret number per spike. However, the molecular basis underlying this specific spike morphology is completely unknown.Through map-based cloning, the causal genes for TRS trait in Zang734 were isolated. Furthermore, using CRISPR/Cas9-based gene mutation, transcriptome sequencing and proteinprotein interaction, the downstream signalling networks related to spikelet formation and awn elongation were defined.Results showed that the null mutation in WFZP-A together with deletion of WFZP-D led to the TRS trait in Zang734. More interestingly, WFZP plays a dual role in simultaneously repressing spikelet formation gene TaBA1 and activating awn development genes, basically through the recruitments of chromatin remodelling elements and the Mediator complex.Our findings provide insights into the molecular bases by which WFZP suppresses spikelet formation but promotes awn elongation and, more importantly, define WFZP-D as a favourable gene for high-yield crop breeding.

Summary The spikelet number and heading date are two crucial and correlated traits for yield in wheat. Here, a quantitative trait locus (QTL) analysis was conducted in F 8 recombinant inbred lines (RILs) derived from crossing two common wheats with different spikelet numbers. A total of 15 stable QTL influencing total spikelet number (TSN) and heading date (HD) were detected. Notably, FT‐D1 , a well‐known flowering time gene in wheat, was located within the finely mapped interval of a major QTL on 7DS ( QTsn/Hd.cau‐7D ). A causal indel of one G in the third exon of FT‐D1 was significantly associated with total spikelet number and heading date. Consistently, CRISPR/Cas9 mutant lines with homozygous mutations in FT‐D1 displayed an increase in total spikelet number and heading date when compared with wild type. Moreover, one simple and robust marker developed according to the polymorphic site of FT‐D1 revealed that this one G indel had been preferentially selected to adapt to different environments. Collectively, these data provide further insights into the genetic basis of spikelet number and heading date, and the diagnostic marker of FT‐D1 will be useful for marker‐assisted pyramiding in wheat breeding.

Lateral roots play essential roles in drought tolerance in maize (Zea mays L.). However, the genetic basis for the variation in the number of lateral roots in maize remains elusive. Here, we identified a major quantitative trait locus (QTL), qLRT5-1, controlling lateral root number using a recombinant inbred population from a cross between the maize lines Zong3 (with many lateral roots) and 87-1 (with few lateral roots). Fine-mapping and functional analysis determined that the candidate gene for qLRT5-1, ZmLRT, expresses the primary transcript for the microRNA miR166a. ZmLRT was highly expressed in root tips and lateral root primordia, and knockout and overexpression of ZmLRT increased and decreased lateral root number, respectively. Compared with 87-1, the ZmLRT gene model of Zong3 lacked the second and third exons and contained a 14 bp deletion at the junction between the first exon and intron, which altered the splicing site. In addition, ZmLRT expression was significantly lower in Zong3 than in 87-1, which might be attributed to the insertions of a transposon and over large DNA fragments in the Zong3 ZmLRT promoter region. These mutations decreased the abundance of mature miR166a in Zong3, resulting in increased lateral roots at the seedling stage. Furthermore, miR166a post-transcriptionally repressed five development-related class-III homeodomain-leucine zipper genes. Moreover, knockout of ZmLRT enhanced drought tolerance of maize seedlings. Our study furthers our understanding of the genetic basis of lateral root number variation in maize and highlights ZmLRT as a target for improving drought tolerance in maize.

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