Drought Stress Enhances Up-Regulation of Anthocyanin Biosynthesis in Grapevine leafroll-associated virus 3-Infected in vitro Grapevine (Vitis vinifera) Leaves.

Reddish-purple coloration on the leaf blades and downward rolling of leaf margins are typical symptoms of grapevine leafroll disease (GLD) in red-fruited grapevine cultivars. These typical symptoms are attributed to the expression of genes encoding enzymes for anthocyanins synthesis, and the accumulation of flavonoids in diseased leaves. Drought has been proven to accelerate development of GLD symptoms in virus-infected leaves of grapevine. However, it is not known how drought affects GLD expression nor how anthocyanin biosynthesis in virus-infected leaves is altered. The present study used HPLC to determine the types and levels of anthocyanins, and applied reverse transcription quantitative polymerase chain reaction (RT-qPCR) to analyze the expression of genes encoding enzymes for anthocyanin synthesis. Plantlets of Grapevine leafroll-associated virus 3 (GLRaV-3)-infected Vitis vinifera 'Cabernet Sauvignon' were grown in vitro under PEG-induced drought stress. HPLC found no anthocyanin-related peaks in the healthy plantlets with or without PEG-induced stress, while 11 peaks were detected in the infected plantlets with or without PEG-induced drought stress, but the peaks were significantly higher in infected drought-stressed plantlets. Increased accumulation of total anthocyanin compounds was related to the development of GLD symptoms in the infected plantlets under PEG stress. The highest level of up-regulated gene expression was found in GLRaV-3-infected leaves with PEG-induced drought stress. Analyses of variance and correlation of anthocyanin accumulation with related gene expression levels found that GLRaV-3-infection was the key factor in increased anthocyanin accumulation. This accumulation involved the up-regulation of two key genes, MYBA1 and UFGT, and their expression levels were further enhanced by drought stress.

Responses of In vitro-Grown Plantlets (Vitis vinifera) to Grapevine leafroll-Associated Virus-3 and PEG-Induced Drought Stress.

Stresses caused by viral diseases and drought have long threatened sustainable production of grapevine. These two stresses frequently occur simultaneously in many of grapevine growing regions of the world. We studied responses of in vitro-grown plantlets (Vitis vinifera) to Grapevine leafroll associated virus-3 (GLRaV-3) and PEG-induced drought stress. Results showed that stress induced by either virus infection or drought had negative effects on vegetative growth, caused significant decreases and increases in total soluble protein and free proline, respectively, induced obvious cell membrane damage and cell death, and markedly increased accumulations of [Formula: see text] and H2O2. Co-stress by virus and drought had much severer effects than single stress on the said parameters. Virus infection alone did not cause significant alternations in activities of POD, ROS, and SOD, and contents of MDA, which, however, markedly increased in the plantlets when grown under single drought stress and co-stress by the virus and drought. Levels of ABA increased, while those of IAA decreased in the plantlets stressed by virus infection or drought. Simultaneous stresses by the virus and drought had co-effects on the levels of ABA and IAA. Up-regulation of expressions of ABA biosynthesis genes and down-regulation of expressions of IAA biosynthesis genes were responsible for the alternations of ABA and IAA levels induced by either the virus infection or drought stress and co-stress by them. Experimental strategies established in the present study using in vitro system facilitate investigations on 'pure' biotic and abiotic stress on plants. The results obtained here provide new insights into adverse effects of stress induced by virus and drought, in single and particularly their combination, on plants, and allow us to re-orientate agricultural managements toward sustainable development of the agriculture.

Different biosynthesis patterns among flavonoid 3-glycosides with distinct effects on accumulation of other flavonoid metabolites in pears (Pyrus bretschneideri Rehd.).

Flavonoid biosynthesis profile was clarified by fruit bagging and re-exposure treatments in the green Chinese pear 'Zaosu' (Pyrus bretschneideri Rehd.) and its red mutant 'Red Zaosu'. Two distinct biosynthesis patterns of flavonoid 3-glycosides were found in 'Zaosu' pear. By comparison with 'Red Zaosu', the biosynthesis of flavonoid 3-galactosides and flavonoid 3-arabinosides were inhibited by bagging and these compounds only re-accumulated to a small degree in the fruit peel of 'Zaosu' after the bags were removed. In contrast, the biosynthesis of flavonoid 3-gluctosides and flavonoid 3-rutinosides was reduced by bagging and then increased when the fruits were re-exposed to sunlight. A combination of correlation, multicollinearity test and partial-correlation analyses among major flavonoid metabolites indicated that biosynthesis of each phenolic compound was independent in 'Zaosu' pear, except for the positive correlation between flavonoid 3-rutincosides and flavanols. In contrast with the green pear cultivar, almost all phenolic compounds in the red mutant had similar biosynthesis patterns except for arbutin. However, only the biosynthesis of flavonoid 3-galactosides was relatively independent and strongly affected the synthesis of the other phenolic compounds. Therefore, we propose a hypothesis that the strong accumulation of flavonoid 3-galactosides stimulated the biosynthesis of other flavonoid compounds in the red mutant and, therefore, caused systemic variation of flavonoid biosynthesis profiles between 'Zaosu' and its red mutant. This hypothesis had been further demonstrated by the enzyme activity of UFGT, and transcript levels of flavonoid biosynthetic genes and been well tested by a stepwise linear regression forecasting model. The gene that encodes flavonoid 3-galacosyltransferase was also identified and isolated from the pear genome.

[Choline chloride protects cell membrane and the photosynthetic apparatus in cucumber seedling leaves at low temperature and weak light].

Choline chloride 1.07 mmol/L treatment diminished the saturated lipid contents of the fatty acid components mainly the phosphatidylglycerol (PG) resulting in the decrease of the saturation of lipid (Table 1), declined the permeability of cell membrane and the production of MDA from lipid peroxidation (Fig.2) in the cucumber seedling leaves under low temperature and weak light (6 degrees C, PFD 100 micromol m(-2) s(-1)). Furthermore, the choline chloride treatment alleviated the degradation of chlorophyll pigments especially chlorophyll b, the decrease in maximum photochemical efficiency (Fv/Fm), the capture efficiency of excited energy (Fv'/Fm'), the photochemical quenching coefficient (q(p)) and the actual photochemical efficiency (Phi PSII) of PSII (Table 2, Fig.3A, B & C), and decreases in activity of antioxidant enzymes such as POD, APX and CAT (Fig.4) in chilled leaves under weak light. In addition, choline chloride treatment increased the non-photochemical quenching (NPQ) (Fig.3D) and the proline content (Fig.5) in chilled leaves under weak light. The above results indicate that choline chloride protected the cell membrane and the photosynthetic apparatus in cucumber seedling leaves from chilling stress in weak light.

[Application of the fast chlorophyll fluorescence induction dynamics analysis in photosynthesis study].

The changes in PSII performance of the photosynthetic apparatus caused by environmental stress or senescence have been explored widely by applying the chlorophyll fluorescence technique, mainly by using the modulated fluorometer. In recent years, an alternative approach via analyzing chlorophyll a fluorescence transient using the continuous excitation fluorometer has been developed, which offers more information that cannot be obtained by the modulated fluorometry. The JIP-test based on the theory of energy fluxes in biomembranes has been widely used to analyze the chlorophyll a fluorescence kinetics transient helping researchers to have a deeper insight into the primary photochemical reaction in the photosynthetic apparatus. In this paper, the chlorophyll a fluorescence transient and its significance, the parameters involved and their significance in the JIP-test, and the application of the fast chlorophyll fluorescence induction dynamics analysis in photosynthesis study are introduced combining some results of the author's.

[Effects of chitosan treatment on physiological and biochemical characteristics in cucumber seedlings under low temperature].

Chitosan 50 mg/L treatment alleviated the low temperature injury of cucumber seedling membrane. The chitosan treatment reduced electrolyte leakage and the MDA content of cucumber leaves and alleviated the decreases in photosynthetic rate, the photochemical efficiency of photosystem II (PhiPSII), the photochemical quenching of fluorescence (q(P)) and the efficiency of excitation energy captured by the open photosystem II reaction centers (F(v)'/F(m)') under low temperature (6 degrees C). At the same time, the chitosan treatment enhanced the antioxidant enzymatic activities and increased the proline and soluble protein contents in cucumber leaves under low temperature. The results indicated that chitosan treatment improved cold resistance of cucumber seedlings,which protected the membrane system, improved the capability of eliminating active oxygen species and alleviated the damage to photosynthetic organization under low temperature.