[Effects of exogenous ABA and GA3 on sugar concentration in flesh of cara cara navel orange].
Wang Gui-yuan,Xia Ren-xue,Zeng Xiang-guo,Wu Qiang-sheng
Ying yong sheng tai xue bao = The journal of applied ecology
The concentration of glucose, fructose, sucrose and total sugar were determined after exogenous ABA and GA3 treatment during young period of fruit and before fruit coloring in flesh of Cara Cara Navel Orange. The results showed that 10 mg x L(-1) ABA treatment improved glucose, fructose and total sugar concentration significantly or very significantly, 50 mg x L(-1) ABA treatment improved sucrose concentration very significantly, but 100 mg x L(-1) ABA treatment reduced glucose concentration very significantly. GA3 treatment of lower and middle concentrations (10, 50 and 250 mg x L(-1)) improved sucrose concentration very significantly, 10 mg x L(-1) GA3 treatment had no remarkable effect on glucose and fructose concentration but improved total sugar concentration very significantly, GA3 treatment of 50, 250 and 500 mg x L(-1) decreased glucose, fructose and total sugar concentration very significantly. Therefore, ABA treatment of lower concentration could improve one or several kinds of sugar concentration, but GA3 treatment of higher concentration (250 and 500 mg x L(-1)) prohibited sugar accumulation in flesh of Cara Cara Navel Orange seriously.
The involvement of hexokinase in the coordinated regulation of glucose and gibberellin on cell wall invertase and sucrose synthesis in grape berry.
Zhang Yujing,Zhen Lili,Tan Xi,Li Limei,Wang Xiuqin
Molecular biology reports
In plants, hexokinase (HXK, EC 188.8.131.52), an enzyme normally involved in hexose phosphorylation, plays an important role in sugar sensing and signaling. The hexokinase activity of grape HXKs was confirmed by functional complementation of the hexokinase-deficient yeast strain YSH7.4-3C (hxk1, hxk2, glk1). HXK1 and HXK2 were able to complement this mutant. The subcellular localization of HXK1 and HXK2, observed with green fluorescent protein fusion constructs, indicated that HXK1 localized to the cytosol while HXK2 was a nuclear-targeted hexokinase. Gibberellin (GA3) control various processes across plant life and has been involved in sugar accumulation. The coordinated regulation of exogenous GA3 with Glc on CWINV, SuSy1, or SuSy2 expressions indicated that GA3 can relieve the repression of Glc on CWINV or SuSy1 expression, and the repression of GA3 on SuSy2 expression overrides the Glc-inductive effect, resulting in the down-regulation of SuSy2 expression. It was concluded that GA3 negatively interfere with Glc signal transduction depending on hexokinase phosphorylation. GA3 might regulate CWINV, SuSy1 or SuSy2 expression to in order to maintain an intracellular sugar levels and normal cell metabolism. Our results provide new insights into the crosstalk mechanism of GA3 and Glc signaling depending on hexokinase in grape berry sugar accumulation.
ABA and GA3 increase carbon allocation in different organs of grapevine plants by inducing accumulation of non-structural carbohydrates in leaves, enhancement of phloem area and expression of sugar transporters.
Murcia Germán,Pontin Mariela,Reinoso Herminda,Baraldi Rita,Bertazza Gianpaolo,Gómez-Talquenca Sebastián,Bottini Rubén,Piccoli Patricia N
Grape quality for winemaking depends on sugar accumulation and metabolism in berries. Abscisic acid (ABA) and gibberellins (GAs) have been reported to control sugar allocation in economically important crops, although the mechanisms involved are still unknown. The present study tested if ABA and gibberellin A3 (GA3) enhance carbon allocation in fruits of grapevines by modifying phloem loading, phloem area and expression of sugar transporters in leaves and berries. Pot-grown Vitis vinifera cv. Malbec plants were sprayed with ABA and GA3 solutions. The amount of soluble sugars in leaves and berries related to photosynthesis were examined at three points of berry growth: pre-veraison, full veraison and post-veraison. Starch levels and amylase activity in leaves, gene expression of sugar transporters in leaves and berries and phloem anatomy were examined at full veraison. Accumulation of glucose and fructose in berries was hastened in ABA-treated plants at the stage of full veraison, which was correlated with enhancement of Vitis vinifera HEXOSE TRANSPORTER 2 (VvHT2) and Vitis vinifera HEXOSE TRANSPORTER 6 (VvHT6) gene expression, increases of phloem area and sucrose content in leaves. On the other hand, GA3 increased the quantity of photoassimilates delivered to the stem thus increasing xylem growth. In conclusion, stimulation of sugar transport by ABA and GA3 to berries and stems, respectively, was due to build-up of non-structural carbohydrates in leaves, modifications in phloem tissue and modulation in gene expression of sugar transporters.