The abscisic acid (ABA) has a key role in the regulation of grapevine fruit ripening, but the cellular and molecular biological mechanism of the hormone action in the fruit ripening remains unknown. By means of differential centrifugation, microsomes were prepared from Kyoho grapevine (Vitis vinifera L. × V. Labrusca L.) berries, and using the microsomes, we have obtained evidence for the occurrence of specific ABA-binding sites on the membranes with the microvolume radio-ligand binding assay. The binding sites had saturability, high affinity, and low capacity. The results of trypsin and dithiothreitol treatments to the microsomes suggested that ABA binding sites had the properties of proteins that might have disulfide group located at or near the binding site. The binding maximum amount of ABA in the microsomes was at pH 6.0 and the activity of ABA binding proteins was higher at 25 than at 0°C (temperature). The amount of ABA bound reached 54% of the ABA binding maximum (Bmax) for 10 minutes of incubation and Bmax reached for 30 minutes. The dissociation constant (Ka) and Bmax of ABA binding proteins in the microsomes were 17.5 nmol/L and 98.4 fmol/mg protein, respectively.
Da-Peng Zhang, Zi-Lian Zhang, Jia Chen, and Jiang Lu
Da-Peng Zhang, Zi-Lian Zhang, Jia Chen, and Jiang Lu
By using the micro-volume radio-ligand binding essay, the changes in the kinetic characteristics of the abscisic acid (ABA)-binding protein(s) of the Kyhoh grapevine (Vitis vinifera × V. labrusca) fruit during the different stages of fruit development have been studied. The changes in the berry volume growth, concentration of sugar, organic acids, and ABA in fruit mesocarp have been surveyed, especially for studies of ABA-binding protein. The dissociation constant (Kd) and ABA binding maximum (Bmax) were determined by the Scatchard plots for ABA binding in microsomes of the fruit. They are Kd = 17.5, 50.0, 6.3, 13.3 nmol·L–1; Bmax = 98.6, 523.0, 41.6, 85.4 μmol·mg–1 protein, respectively, for the fruit developmental phase I, II, veraison, and phase III. The Scatchard plots showed a rectilinear function for all of the developmental phases including veraison, which suggests the sole ABA-binding site of high affinity for ABA in the fruit microsomes, but this site could either be only one kind of the same protein or consist of more kinds of different proteins for different developmental stages. The binding affinity of ABA-binding protein(s) for ABA was shown to be higher at veraison time than during other developmental phases; this binding affinity increased nearly by 10 times from phase II to veraison, while the concentration (Bmax) of the ABA-binding protein(s) decreased to the minimum at veraison. The very low concentration of ABA at veraison may be able to trigger the onset of fruit ripening due to the increase of the binding affinity of ABA-binding protein(s) for ABA at this time. The possible functions of the ABA-binding protein(s) for fruit development during the different developmental stages were discussed, and it is suggested that the protein(s) detected could be the putative ABA receptor(s) or transporter(s) for the action of this plant hormone in grapevine.
Min Wang, Wenrui Liu, Biao Jiang, Qingwu Peng, Xiaoming He, Zhaojun Liang, and Yu’e Lin
Heat stress (HS) negatively influences plant development and growth, especially production and quality. Cucumber is a widely cultivated plant in the gourd family Cucurbitaceae that is often exposed to high temperatures during summer and protected cultivation. In this study, we performed whole-genome re-sequencing of two pools, one heat-tolerant and one heat-sensitive, of the F2 population derived from L-9 (heat-resistant) and A-16 (heat-sensitive). The genetic analysis showed that the heat resistance of L-9 cucumber seedlings was controlled by a single recessive gene. By combining bulked segregant analysis (BSA) technology, the crucial gene related to HS was preliminarily mapped to a 1.08-Mb region on chromosome 1. To fine-map the locus, Indel markers were designed according to the genomic sequence. Finally, the gene was narrowed to a 550-kb region flanked by two Indel markers, namely Indel-H90 and Indel-H224, that contained 56 candidate genes. Re-sequencing results indicated that 10 candidate genes among the 56 in the candidate region showed single base pair differences in the exons. Quantitative reverse-transcription polymerase chain reaction showed that 6 genes among the 10 candidate genes were significantly decreased when exposed to high temperatures. These results not only were useful for the isolation and characterization of the key genes involved in HS but also provided a basis for understanding the mechanism of heat tolerance regulation.
Yihua Chen, Peng Jiang, Shivegowda Thammannagowda, Haiying Liang, and H. Dayton Wilde
We investigated the FT/TFL1 family of peach (Prunus persica), a gene family that regulates floral induction in annual and perennial plants. The peach terminal flower 1 gene (PpTFL1) was expressed in a developmental and tissue-specific pattern that, overall, was similar to that of TFL1 orthologs in other woody Rosaceae species. Consistent with a role as a floral inhibitor, ectopic expression of PpTFL1 in arabidopsis (Arabidopsis thaliana) delayed flowering and prolonged vegetative growth. Other members of the peach FT/TFL1 family were identified from the sequenced genome, including orthologs of flowering locus T, centroradialis, brother of ft, and mother of ft and tfl. Sequence analysis found that peach FT/TFL1 family members were more similar to orthologous genes across the Rosaceae than to each other. Together these results suggest that information on genes that regulate flowering in peach could be applied to other Rosaceae species, particularly ornamentals.
Xing-Zheng Fu, Fei Xing, Li Cao, Chang-Pin Chun, Li-Li Ling, Cai-Lun Jiang, and Liang-Zhi Peng
To compare the effects of various zinc (Zn) foliar fertilizers on correcting citrus Zn deficiency and to explore an effective correcting method, three common Zn fertilizers, Zn sulfate heptahydrate (ZnSO4.7H2O), Zn chloride (ZnCl2), and Zn nitrate hexahydrate [Zn(NO3)2.6H2O], were selected to spray the Zn-deficient citrus leaves, tested at different concentrations, with or without organosilicone surfactant. Zn content, chlorophyll levels, and photosynthesis characteristics of leaves were analyzed. Leaf Zn content was significantly increased with increase of the sprayed Zn concentration of the three Zn fertilizers. However, when the sprayed Zn concentration of ZnSO4.7H2O exceeded 200 mg·L−1, and Zn concentration of ZnCl2 or Zn(NO3)2.6H2O exceeded 100 mg·L−1, obvious necrotic spots formed on leaves. This necrosis disappeared when 0.025% organosilicone was added to the three Zn fertilizer solutions, even at a Zn concentration of 250 mg·L−1. Meanwhile, the Zn contents of leaves increased one to four times for these treatments. Furthermore, foliar application of the three Zn fertilizers significantly improved chlorophyll levels and photosynthetic capacity of Zn-deficient leaves. The data of chlorophyll and photosynthesis characteristics indicate that the correcting effect of ZnCl2 and Zn(NO3)2.6H2O is better than that of ZnSO4.7H2O, and could be further improved via supplement of organosilicone. In conclusion, ZnCl2 or Zn(NO3)2.6H2O containing 250 mg·L−1 of Zn and supplemented with 0.025% organosilicone is a safe and effective formulation of Zn foliar fertilizer for correcting citrus Zn deficiency.