The glossy varieties (A14 and Jing 2001) and glaucous varieties (Fanmai 5 and Shanken 99) of wheat (Triticum aestivum L.) were selected for evaluation of developmental changes in the composition and morphology of cuticular waxes on leaves and spikes. The results provide us with two different wax development patterns between leaf and spike. The general accumulation trend of the total wax load on leaf and spike surfaces is first to increase and then decrease during the development growth period, but these changes were caused by different compound classes between leaf and spike. Developmental changes of leaf waxes were mainly the result of variations in composition of alcohols and alkanes. In addition, diketones were the third important contributor to the leaf wax changes in the glaucous varieties. Alkanes and diketones were the two major compound classes that caused the developmental changes of spike waxes. For leaf waxes, β- and OH-β-diketones were first detected in flag leaves from 200-day-old plants, and the amounts of β- and OH-β-diketones were significantly higher in glaucous varieties compared with glossy varieties. In spike waxes, β-diketone existed in all varieties, but OH-β-diketone was detectable only in the glaucous varieties. Unexpectedly, the glaucous variety Fanmai 5 yielded large amounts of OH-β-diketone. There was a significant shift in the chain length distribution of alkanes between early stage leaf and flag leaf. Unlike C28 alcohol being the dominant chain length in leaf waxes, the dominant alcohol chain length of spikes was C24 or C26 depending on varieties. Epicuticular wax crystals on wheat leaf and glume were comprised of platelets and tubules, and the crystal morphology changed constantly throughout plant growth, especially the abaxial leaf crystals. Moreover, our results suggested that platelets and tubules on glume surfaces could be formed rapidly within a few days.

No abstract

The vacuolar type H+-ATPase (V-type H+-ATPase) plays important roles in establishing an electrochemical H+-gradient across tonoplast, energizing Na+ sequestration into the central vacuole, and enhancing salt stress tolerance in plants. In this paper, a putative E subunit of the V-type H+-ATPase gene, W36 was isolated from stress-induced wheat de novo transcriptome sequencing combining with 5'-RACE and RT-PCR methods. The full-length of W36 gene was 1097 bp, which contained a 681 bp open reading frame (ORF) and encoded 227 amino acids. Southern blot analysis indicated that W36 was a single-copy gene. The quantitative real-time PCR (qRT-PCR) analysis revealed that the expression level of W36 could be upregulated by drought, cold, salt, and exogenous ABA treatment. A subcellular localization assay showed that the W36 protein accumulated in the cytoplasm. Isolation of the W36 promoter revealed some cis-acting elements responding to abiotic stresses. Transgenic Arabidopsis plants overexpressing W36 were enhanced salt and mannitol tolerance. These results indicate that W36 is involved in the plant response to osmotic stress.

Compared to C3 species, C4 plants showed higher photosynthetic capacity as well as water and nitrogen use efficiency due to the presence of the C4 photosynthetic pathway. Previous studies have shown that all genes required for the C4 photosynthetic pathway exist in the genomes of C3 species and are expressed. In this study, the genes encoding six key C4 photosynthetic pathway enzymes (β-CA, PEPC, ME, MDH, RbcS, and PPDK) in the genomes of five important gramineous crops (C4: maize, foxtail millet, and sorghum; C3: rice and wheat) were systematically identified and compared. Based on sequence characteristics and evolutionary relationships, their C4 functional gene copies were distinguished from non-photosynthetic functional gene copies. Furthermore, multiple sequence alignment revealed important sites affecting the activities of PEPC and RbcS between the C3 and C4 species. Comparisons of expression characteristics confirmed that the expression patterns of non-photosynthetic gene copies were relatively conserved among species, while C4 gene copies in C4 species acquired new tissue expression patterns during evolution. Additionally, multiple sequence features that may affect C4 gene expression and subcellular localization were found in the coding and promoter regions. Our work emphasized the diversity of the evolution of different genes in the C4 photosynthetic pathway and confirmed that the specific high expression in the leaf and appropriate intracellular distribution were the keys to the evolution of C4 photosynthesis. The results of this study will help determine the evolutionary mechanism of the C4 photosynthetic pathway in Gramineae and provide references for the transformation of C4 photosynthetic pathways in wheat, rice, and other major C3 cereal crops.

Background Phosphate (Pi) deficiency severely affects crop growth and productivity, including wheat, therefore it is necessary to develop cultivars with enhanced Pi-deficiency tolerance. However, the underlying mechanism of Pi-deficiency tolerance in wheat is still elusive. Two contrasting wheat cultivars, low-Pi tolerant Kenong199 (KN199) and low-Pi sensitive Chinese Spring (CS) were used to reveal adaptations in response to Pi deficiency at the morphological, physiological, metabolic, and molecular levels. Results KN199 was more tolerant to Pi deficiency than CS with significantly increased root biomass and R/S ratio. Root traits, the total root length, total surface area, and total volume, were remarkably enhanced by Pi deficiency in KN199. The shoot soluble Pi and total P concentrations of KN199 were all significantly higher than these of CS, but not in roots. In KN199, high Pi level in shoots is a higher priority than that in roots under Pi deficiency. It was probably due to differentially regulation in the miR399-mediated signaling network between the shoots of the two cultivars. The Pi deficiency-induced root architecture adaptation in KN199 was attributed to the regulation of the hormone-mediated signaling (ethylene, gibberellin, and jasmonates). The expression of genes associated with root development and Pi uptake was enhanced in KN199. Some primary metabolites (amino acids and organic acids) were significantly accumulated in roots of KN199 under Pi deficiency. Conclusions The low-Pi tolerant wheat cultivar KN199 possessed greater morphological and primary metabolic adaptations in roots than CS under Pi deficiency. The adaption and the underlying molecular mechanism in wheat provide a better understanding of the Pi-deficiency tolerance and the strategies for improving Pi efficiency in wheat.