Zaijun Yang

Proper development of floral organs is essential for reproductive success and grain yield in wheat. However, the molecular mechanisms regulating wheat floral organ development remain largely unknown. In this study, we characterized the role of the wheat TaEPFL1 gene in floral organ development and its association with ethylene signaling. TaEPFL1 was highly expressed in immature spikes of the pistillody mutant HTS-1, particularly during the pistil and stamen specification stages. Its expression was responsive to both exogenous ethylene and the ethylene inhibitor 1-Methylcyclopropene (1-MCP). Overexpression of TaEPFL1 in transgenic wheat led to shortened stamens, defective pistils, male sterility, and complete reproductive failure. Histological analysis revealed delayed tapetum degradation, indicating disrupted programmed cell death (PCD). Gas chromatography (GC) showed significantly reduced ethylene production and release in TaEPFL1-overexpressing lines. Similar floral defects were observed in wild-type plants treated with 1-MCP. Transcriptome and qRT-PCR analyses further confirmed downregulation of multiple ethylene biosynthesis-related genes, including three homologs of TaACO. These results suggest that TaEPFL1 negatively regulates ethylene biosynthesis by repressing TaACO expression, thereby impairing floral organ differentiation. We propose a feedback model in which ethylene induces TaEPFL1, which in turn suppresses ethylene production to maintain hormonal homeostasis. This study reveals a novel regulatory mechanism linking TaEPFL1 to ethylene-mediated floral development and provides new insights for improving wheat fertility through molecular breeding.

TaWI12 is a member of the wound-induced (WI) protein family, which has been implicated in plant stress responses and developmental processes. Wheat (Triticum aestivum L.) is a crucial staple crop upon which human sustenance relies. Consequently, investigating the developmental mechanisms of pistils and stamens in wheat is profoundly significant for enhancing wheat characteristics and boosting productivity. In this study, we cloned TaWI12, from common wheat and observed a significant resemblance among the three homoeologs of TaWI12. The open reading frames (ORFs) of TaWI12-4A, TaWI12-4B and TaWI12-4D were 408 bp, 417 bp and 417 bp, respectively, and encoded 135, 138 and 138 amino acids, respectively. The phylogenetic tree revealed a high degree of homology between the protein sequences of TaWI12 and the wound-induced proteins of Hordeum vulgare (KAI4994568) and Aegilops tauschii (XP_020196548). To clarify the characteristics and functions of TaWI12 homoeologs, we obtained transgenic positive plants of Arabidopsis thaliana and observed significant filament shortening and decrease. Simultaneously, we used the CRISPR/Cas9 system to generate mutant plants via the modification of three homoeologs of TaWI12 in wheat. We noticed two distinct phenotypic differences in the knockout mutant. First, we observed the different degrees of homologous conversion of stamens to pistils in the single mutant TaWI12-4D. Second, we observed leaf cracking in both the single mutant TaWI12-4A and the double mutants TaWI12-4A and TaWI12-4D. Our findings further revealed that TaWI12 plays an important role in flower development, which is important for revealing the molecular mechanisms of pistil and stamen development in wheat and has important application value for high-yield wheat breeding. TaWI12 overexpression in Arabidopsis caused filament shortening and decreasing. 1 bp insertion or deletion in upstream of ATG increased the expression of TaWI12 and caused varying degrees of pistillody traits in wheat. Utilizing CRISPR/Cas9 technology to modify TaWI12 in the coding region caused varying degrees of leaf cracking in wheat.

Multi-pistil trait in wheat is of great potential value in plant development research and crop breeding. Our previous studies identified the Pis1 locus that causes three pistils in wheat by genetic mapping using multiple DNA marker systems. However, there are still 26 candidate genes on the locus, and the causal gene remains to be found. In this study, we aimed to approach the molecular mechanism of multi-pistil formation. Comparative RNA sequencing (RNA-Seq) during the pistil formation was undertaken in four wheat lines: a three-pistil mutant TP, a single-pistil TILLING mutant of TP (SP), a three-pistil near-isogenic line CM28TP with the background of cultivar Chunmai 28 (CM28), and CM28. Electron microscopic analysis specified probable developmental stages of young spikes for the three-pistil formation. mRNA sequencing in the young spikes of the four lines represented 253 down-regulated genes and 98 up-regulated genes in both three-pistil lines, which included six potential genes for ovary development. Weighted gene co-expression analysis represented three-pistil trait-associated transcription factor-like genes, among which one hub gene, ARF5, was the most highlighted. ARF5 is on the Pis1 locus and an orthologue of MONOPTEROS which mediates tissue development in Arabidopsis. qRT-PCR validation implies that the deficiency of ARF5 underlies the three-pistil formation in wheat.

Poaceae is the most prominent monocot family that contains the primary cereal crops wheat, rice, and maize. These cereal species exhibit physiological diversity, such as different photosynthetic systems and environmental stress tolerance. Phosphoenolpyruvate carboxylase (PEPC) in Poaceae is encoded by a small multigene family and plays a central role in C₄-photosynthesis and dicarboxylic acid metabolism. Here, to better understand the molecular basis of the cereal species diversity, we analyzed the PEPC gene family in wheat together with other grass species. We could designate seven plant-type and one bacterial-type grass PEPC groups, ppc1a, ppc1b, ppc2a, ppc2b, ppc3, ppc4, ppcC₄, and ppc-b, respectively, among which ppc1b is an uncharacterized type of PEPC. Evolutionary inference revealed that these PEPCs were derived from five types of ancient PEPCs (ppc1, ppc2, ppc3, ppc4, and ppc-b) in three chromosomal blocks of the ancestral Poaceae genome. C₄-photosynthetic PEPC (ppcC₄) had evolved from ppc1b, which seemed to be arisen by a chromosomal duplication event. We observed that ppc1b was lost in many Oryza species but preserved in Pooideae after natural selection. In silico analysis of cereal RNA-Seq data highlighted the preferential expression of ppc1b in upper ground organs, selective up-regulation of ppc1b under osmotic stress conditions, and nitrogen response of ppc1b. Characterization of wheat ppc1b showed high levels of gene expression in young leaves, transcriptional responses under nitrogen and abiotic stress, and the presence of a Dof1 binding site, similar to ppcC₄ in maize. Our results indicate the evolving status of Poaceae PEPCs and suggest the functional association of ppc1-derivatives with adaptation to environmental changes.

Comparative metabolomics and transcriptomics of pistils, stamens and pistilloid stamens widen key knowledge of pistil and stamen development in wheat. | Yan Yu, Zheng Song Peng, Ji Peng Qu, Zhen Yong Chen, Shu Hong Wei, Ming Li Liao, Li Zhang, Zai Jun Yang<a target=

Members of the EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) family play diverse roles in plant growth and development, including the guidance of inflorescence architecture and pedicel length. In this work, we identified and characterized the EFPL gene TaEPFL1 from the wheat pistillody mutant HTS-1. Sequence alignment and phylogenetic analysis indicated that TaEPFL1 belongs to the EPFL1 gene. Quantitative real-time RT-PCR analysis showed that the TaEPFL1 gene is expressed at an abnormally high level in pistillody stamens compared with that in pistils and stamens. Heterologous expression of the TaEPFL1 gene in Arabidopsis caused shortened filaments and pedicels and might reduce the level of AtACO2 gene expression. These results suggest that TaEPFL1 plays an important role in the development of stamen and that overexpression of TaEPFL1 results in abnormal stamens. We deduced that the overexpression of the TaEPFL1 gene may contribute to the homeotic transformation of stamens into pistils or pistil-like structures in wheat. These data offer insights into the molecular mechanism of pistillody mutation in wheat.