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  • Author or Editor: Hui-Rong Hu x
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‘Korla’ fragrant pear (Pyrus sinkiangensis T.T. Yu) variety has shown severe coarse skin in recent years. The intrinsic quality of its coarse fruit shows an increase in the number of stone cells and poor taste. In this study, stone cells and the cell wall of coarse pear (CP) and normal pear (NP) during various development stages were compared using paraffin-sectioning and transmission electron microscopy (TEM), and the relationships between lignin-related genes and stone cell formation and cell wall thickening were also analyzed. Our results show that giant stone cells are formed and distributed in the core of pear, whereas many of these crack 60 days after flowering (DAF). The period of stone cell fragmentation occurs later in CP fruits than in NP fruits. Parenchyma cell wall development in CP and NP fruits varies from 120 DAF to maturity. The parenchyma cell wall of CP fruits thickens, whereas that of NP fruits is thinner during the same period. The expression pattern of five genes (Pp4CL1-l, PpHCT-l, Pp4CL2-l, PpPOD4, and PpPOD25) coincides with changes in stone cell content in the pulp. Correlation analysis demonstrates a significant correlation between stone cell content and the expression level of the five genes (ρ < 0.05). In addition, the expression of those five genes and PpCCR1 genes in CP fruits significantly increases during maturation and is highly correlated with the thickness of the parenchyma cell wall. The aim of this work is to provide insights into the mechanism of stone cell and parenchyma cell wall development in pear fruits and identify important candidate genes to regulate the quality of fruit texture using bioengineering methods.

Open Access

A set of Petunia hybrida plants encompassing a range of ploidy levels was developed through colchicine-mediated induction of chromosome doubling. The resulting double-flower tetraploid plants were cross-hybridized with inbred single-flower diploid lines to generate F1 populations with segregation for ploidy level and flower type. The initial in vivo application of colchicine to seedling apical tips produced mixoploid plants of petunia at a high rate of efficiency. Thus, 95% of the shoot tips treated with colchicine for 48 h resulted in polyploid mutant plants, and no difference in this efficiency was observed using concentrations of colchicine between 0.2 and 2.0 mg·mL−1. Of the polyploid plants, 10% were found to be tetraploid and 85% were mixoploid (chimeric). Compared with their diploid counterparts, polyploid plants underwent reduced elongation growth during the first 2 weeks and had thicker stems and shorter internodes resulting in dwarfing of the whole plant. In extreme cases, very slow growth rates produced stunted plantlets. Polyploid plants also had larger, thicker leaves and, in some cases, the leaves that developed after 1 month of growth appeared seriously malformed. Octoploid plants were also obtained and these tended to have more extreme phenotypes. Pure tetraploid plants of double-flower petunia were isolated by the in vitro culture of explants from the initial chimeric tetraploid mutants. These were crossed with three inbred single-flower diploid lines (S1, S2, and S3) thereby generating F1 populations that showed segregation for flower type and ploidy level and included the generation of triploid plants. In the tetraploid plants, flower diameter and the number of flower petals were not changed significantly (P > 0.05) compared with the original diploid double-flower plants, but observation of the pollen grains revealed segregation for size consistent with the increased ploidy level. Analysis of the F1 progeny plants also indicated that chromosome number is not necessary but sufficient to cause the production of semidouble-flowered plants. Flower color and flower diameter were also analyzed in the F1 progeny and complex patterns of inheritance were inferred. In addition to single and double flowers, semidouble-flowered plants were also suggested to be generated by the hybridization of 2n or 3n pollen from the double-flower tetraploid plants with the single-flower diploid lines.

Free access

We studied the effects of exogenous spermidine (Spd) on plant growth and nitrogen metabolism in two cultivars of tomato (Solanum lycopersicum) that have differential sensitivity to mixed salinity-alkalinity stress: ‘Jinpeng Chaoguan’ (salt-tolerant) and ‘Zhongza No. 9’ (salt-sensitive). Seedling growth of both tomato cultivars was inhibited by salinity-alkalinity stress, but Spd treatment alleviated the growth reduction to some extent, especially in ‘Zhongza No. 9’. Exogenous Spd may help reduce stress-induced increases in free amino acids, ammonium (NH4 +) contents, and NADH-dependent glutamate dehydrogenase (NADH-GDH) activities; depress stress-induced decreases in soluble protein and nitrate content; and depress nitrate reductase, nitrite reductase, glutamine synthetase (GS), NADH-dependent glutamate synthase (NADH-GOGAT), glutamate oxaloacetate transaminase (GOT), and glutamate pyruvate transaminase (GPT) activities, especially for ‘Zhongza No. 9’. Based on our results, we suggest that exogenous Spd promotes the assimilation of excess toxic NH4 + by coordinating and strengthening the synergistic action of NADH-GDH, GS/NADH-GOGAT, and transamination pathways, all during saline-alkaline stress. Subsequently, NH4 + and its related enzymes (GDH, GS, GOGAT, GOT, and GPT), in vivo, are maintained in a proper and balanced state to enable mitigation of stress-resulted damages. These results suggest that exogenous Spd treatment can relieve nitrogen metabolic disturbances caused by salinity-alkalinity stress and eventually promote plant growth.

Free access