The WUSCHEL-related homeobox (WOX) is a family of plant-specific transcription factors, with important functions, such as regulating the dynamic balance of division and differentiation of plant stem cells and plant organ development. We identified 14 distinct TaWOX genes in the wheat (Triticum aestivum L.) genome, based on a genome-wide scan approach. All of the genes under evaluation had positional homoeologs on subgenomes A, B and D except TaWUS and TaWOX14. Both TaWOX14a and TaWOX14d had a paralogous copy on the same genome due to tandem duplication events. A phylogenetic analysis revealed that TaWOX genes could be divided into three groups. We performed functional characterization of TaWOX genes based on the evolutionary relationships among the WOX gene families of wheat, rice (Oryza sativa L.), and Arabidopsis. An overexpression analysis of TaWUS in Arabidopsis revealed that it affected the development of outer floral whorl organs. The overexpression analysis of TaWOX9 in Arabidopsis revealed that it promoted the root development. In addition, we identified some interaction between the TaWUS and TaWOX9 proteins by screening wheat cDNA expression libraries, which informed directions for further research to determine the functions of TaWUS and TaWOX9. This study represents the first comprehensive data on members of the WOX gene family in wheat.

Chemical hybridization agent (CHA)-induced male sterility is an important tool in crop heterosis. To demonstrate that CHA-SQ-1-induced male sterility is associated with abnormal tapetal and microspore development, the cytology of CHA-SQ-1-treated plant anthers at various developmental stages was studied by light microscopy, scanning and transmission electron microscopy, in situ terminal deoxynucleotidyl transferasemediated dUTP nick end-labelling (TUNEL) assay and DAPI staining. The results indicated that the SQ-1-treated plants underwent premature tapetal programmed cell death (PCD), which was initiated at the early-uninucleate stage of microspore development and continued until the tapetal cells were completely degraded; the process of microspore development was then blocked. Microspores with low-viability (fluorescein diacetate staining) were aborted. The study suggests that premature tapetal PCD is the main cause of pollen abortion. Furthermore, it determines the starting period and a key factor in CHA-SQ-1-induced male sterility at the cell level, and provides cytological evidence to further study the mechanism between PCD and male sterility.

DUOII is a multi-ovary wheat (Triticum aestivum L.) line with two or three pistils and three stamens in each floret. The multi-ovary trait of DUOII is controlled by a dominant gene, whose expression can be suppressed by the heterogeneous cytoplasm of TeZhiI (TZI), a line with the nucleus of common wheat and the cytoplasm of Aegilops. Crosses between female DUOII plants and male TZI plants resulted in multi-ovary F1s; whereas, the reciprocal crosses resulted in mono-ovary F1s. Although the multi-ovary trait is inherited as single trait controlled by a dominant allele in lines with a Triticum cytoplasm, the mechanism by which the special heterogeneous cytoplasm suppresses the expression of multi-ovary is not well understood. Observing the developmental process, we found that the critical stage of additional pistil primordium development was when the young spikes were 2–6 mm long. Then, we compared the quantitative proteomic profiles of 2–6 mm long young spikes obtained from the reciprocal crosses between DUOII and TZI. A total of 90 differentially expressed proteins were identified and analyzed based on their biological functions. These proteins had obvious functional pathways mainly implicated in chloroplast metabolism, nuclear and cell division, plant respiration, protein metabolism, and flower development. Importantly, we identified two key proteins, Flowering Locus K Homology Domain and PEPPER, which are known to play an essential role in the specification of pistil organ identity. By drawing relationships between the 90 differentially expressed proteins, we found that these proteins revealed a complex network which is associated with multi-ovary gene expression under heterogeneous cytoplasmic suppression. Our proteomic analysis has identified certain differentially expressed proteins in 2–6 mm long young spikes, which was the critical stage of additional primordium development. This paper provided a universal proteomic profiling involved in the cytoplasmic suppression of wheat floral meristems; and our findings have laid a solid foundation for further mechanistic studies on the underlying mechanisms that control the heterogeneous cytoplasm-induced suppression of the nuclear multi-ovary gene in wheat.

SQUAMOSApromoter-binding protein (SBP)-box genes encode a family of plant-specific transcription factors that play roles in plant growth and development. The characteristics of SBP-box genes in rice (Oryza sativa) andArabidopsishave been reported, but their potential roles in wheat (Triticum aestivum) are not fully understood. In this study, 48SBP-box genes (TaSBPs) were identified; they were located in all wheat chromosomes except for 4B and 4D. SixTaSBPswere identified as tandem duplication genes that formed three tandem duplication pairs, while 22 were segmentally duplicated genes that formed 16 segmental duplication pairs. Subcellular localization prediction showed TaSBPs were located in nucleus. Among the 48TaSBPs, 24 were predicted to be putative targets ofTamiR156. Phylogenetic analysis showed that TaSBPs, AtSBPs, and OsSBPs that shared similar functions were clustered into the same subgroups. The phylogenetic relationships between the TaSBPs were supported by the identification of highly conserved motifs and gene structures. Four types ofcis-elements––transcription-related, development-related, hormone-related, and abiotic stress-related elements––were found in theTaSBPpromoters. Expression profiles indicated mostTaSBPsparticipate in flower development and abiotic stress responses. This study establishes a foundation for further investigation ofTaSBPgenes and provides novel insights into their biological functions.

This study used semi-thin sectioning and cytochemistry to investigate the relationship between pollen nutrient metabolism and pollen abortion in male sterile lines of wheat induced by SQ-1 (a chemical hybridising agent). Anthers were collected from the tetrad to trinucleate stages, and 4',6-diamidino-2-phenylindole staining was used to visualise nuclei and confirm the development stage. Sudan Black B, periodic acid–Schiff, Coomassie Brilliant Blue, and toluidine blue were used to detect lipids, starch, proteins, and acidic polyanions, respectively. Semi-thin sectioning indicated that nutrient accumulation was much higher in the fertile line 1376 than in the sterile line 1376-PHYMS. Further, no lipids were found in the free microspore stage in the sterile line; however, at the late microspore stage, more proteins and acidic polyanions were found in the sterile line 1376-PHYMS pollen than in the fertile line 1376 pollen. From the binucleate to trinucleate pollen stages, the starch content was low and the intine considerably thinner in the pollen of the 1376-PHYMS line. SQ-1 probably hampered nutrient metabolism in the anthers, leading to decreased nutrient supply and abnormal intine formation, ultimately resulting in pollen abortion. A new mechanism for nutrient absorption, i.e. endocytosis of Ubisch bodies or orbicules by the intine through the germinal aperture, was revealed.