Byoung Yong Moon

Differential expression of rice lipid transfer protein gene(LTP) classes in response to abscisic acid, salt, salicylic acid, and the fungal pathogenMagnaporthe grisea

Rice lipid transfer protein(LTP) genes belong to a complex multigene family and are differentially regulated. The organ specificity of expression for the different classes of riceLTP gene Subfamily I was investigated here.LTPC1 (Class I) was highly expressed in flowers and stems, whileLTPC2 (Class II) showed higher expression in leaves and stems.LTPC3 (Class III) showed higher expression in stems, whereas corresponding mRNA was barely detected in leaves. Treatment of 3-wk-old plants with ABA induced the expression ofLTPC1 andLTPC3 after 1 d. Expression of all threeLTP isoforms was induced in response to salicylic acid. Because some of these genes are reportedly induced by pathogens, we also investigated whether they might be responsive to infection byMagnaporthe grisea. Transcripts ofLTPC1 started to accumulate in the leaves at 8 h after incompatible inoculation, reaching a maximum level at 48 h. In contrast, the response was much slower and weaker after compatible inoculation.

Yield loss and quality degradation of strawberry fruits cultivated under the deficient insolation conditions by shading

Deficient insolation conditions (DICs) frequently occur during the winter and early spring season in Korea and negatively affect crop growth. This study was conducted to investigate changes in the yields and qualities of strawberry fruits under DICs that result from an insufficient input of sunlight. To induce DIC, strawberry plants were treated with 40 or 70% shading by covering the plants with curtains during growth in a plastic greenhouse. The shaded plants were cultivated from March to May of 2012. When the strawberry plants were subjected to the shading treatments, their photosynthesis and fruit yields were significantly reduced. Although the mineral element and organic acid contents of the fruits were not affected by the shading treatments, the total nitrogen (T-N) of the stems and roots were noticeably reduced. Furthermore, the shading treatments of the plants also resulted in reductions in the sugar contents and total phenolics of the fruits. In parallel with these observations, the shading treatments were also found to decrease the antioxidant activities of the fruits as measured with the DPPH assay. We suggest that the DIC-induced losses of strawberry fruit yield resulted from the reduced photosynthetic performances of the plants that were caused by insufficient sunlight.

Recovery from low-temperature photoinhibition is related to dephosphorylation of phosphorylated CP29 rather than zeaxanthin epoxidation in rice leaves

During recovery from chilling-induced photoinhibition in rice leaves, we compared the reactivation kinetics of PSII photochemical efficiency (Fv/Fm) with that of zeaxanthin (Z) epoxidation and the dephosphorylation of CP34 (i.e., the phosphorylated form of CP29). The latter two processes were kinetically similar to the slow increase in Fv/Fm measured in our control leaves. However, the rate of Z epoxidation was significantly retarded by an epoxidase inhibitor, 5 mM salicylaldoxime (SA), without any significant changes in the processes of PSII reactivation and CP34 dephosphorylation. When chilled leaves were incubated at 10°C in the dark, both reactivation and dephosphorylation were significantly blocked, but Z epoxidation was not. Finally, we observed that the kinetics of CP34 dephosphorylation matched very well with those of PSII recovery in two rice cultivars with different chilling sensitivities. These results suggest that PSII reactivation from low-temperature photoinhibition is more closely related to CP34 dephosphorylation than to Z epoxidation.

Arabidopsis lenc1 mutant displays reduced ABA accumulation by low AtNCED3 expression under osmotic stress

The plant hormone, abscisic acid (ABA), is a main signal transducer that confers abiotic stress tolerance to plants. Although the pathway of ABA production and the genes catalyzing its biosynthesis are largely defined, the regulatory mechanism of ABA biosynthesis in response to abiotic stress remains much unknown. In this study, to identify upstream genes regulating ABA biosynthesis involved in abiotic stress signal transduction, Arabidopsis thaliana mutants with altered promoter activity of 9-cis-epoxycarotenoid dioxygenase 3 (NCED3), a key gene in ABA biosynthesis, were identified and characterized. Among selected mutants, lenc1 (for low expression of NCED3 1) after dehydration treatment had lower AtNCED3 promoter activity compared with wild type. lenc1 mutation is recessive and is located on chromosome 4. Expression analysis of AtNCED3 and quantification of ABA levels showed that both the AtNCED3 transcripts and the endogenous ABA in lenc1 were less abundant than in wild type under dehydration treatments. The lenc1 was hypersensitive to methyl viologen (MV), LiCl, NaCl and high light. The aerial part of lenc1 lost water faster than wild type possibly due to a larger stomata opening. Our results suggest LENC1 might act as a positive regulator in AtNCED3 gene expression under osmotic stress.

Correlation between Strawberry (Fragaria ananassa Duch.) Productivity and Photosynthesis-Related Parameters under Various Growth Conditions

In the present study, we investigated changes in chlorophyll fluorescence, photosynthetic parameters and fruit yields, as well as fruit phytochemical accumulation of strawberry (Fragaria ananassa Duch.) that had been cultivated in a greenhouse under different combinations of light intensity and temperature. In plants grown with low light (LL) photosystem II chlorophyll fluorescence was found to increase as compared with those grown under high light (HL). When strawberry plants were grown with temperature higher than 5°C in addition to LL, they showed decrease in non-photochemical quenching (NPQ), photochemical quenching (qP), as well as chlorophyll fluorescence decrease ratio (RFd) when compared with other combinations of light and temperature. Moreover, fruit yield of strawberry was closely correlated with chlorophyll fluorescence-related parameters such as NPQ, qP, and RFd, but not with the maximum efficiency of PS II (Fv/Fm). Although plant groups grown under different combinations of light and temperature showed almost comparable levels of photosynthesis rates (Pr) when irradiated with low-intensity light, they displayed clear differences when measured with higher irradiances. Plants grown under HL with temperature above 10°C showed the highest Pr, in contrast to the plants grown under LL with temperature above 5°C. When the stomatal conductance and the transpiration rate were measured, plants of each treatment showed clear differences even when analyzed with lower irradiances. We also found that fruit production during winter season was more strongly influenced by growth temperature than light intensity. We suggest that fruit productivity of strawberry is closely associated with chlorophyll fluorescence and photosynthesis-related parameters during cultivation under different regimes of temperature and light.

Effect of spermine on the phytochelatin concentration and composition in cadmium-treated roots ofCanavalia lineata seedlings

Effect of spermine on the phytochelatins (PCs) in cadmium-treated roots ofCanavalia lineata seedlings was studied. With the treatment of spermine, total nonprotein thiol (SH) contents decreased by 55% in roots of Cd-treated plants. Glutathione (GSH) synthetase activity was inhibited by 36.8% in roots and cysteine synthase was also inhibited by 9.5% while y-GluCys synthetase activity was not affected. From the PC-Cd complex analyses by gel column chromatography, it was found that Cd+spermine-treated roots contain an additional PC that has low affinity for Cd, in addition to Cd-induced PC whose SH:Cd ratio is 1:1. Spermine affected the PC concentration and composition in the Cd-treated roots ofC. lineata seedlings.

Effects of foliar fertilization containing titanium dioxide on growth, yield and quality of strawberries during cultivation

We addressed the question of whether it is useful to apply a titanium dioxide (TiO2) solution to promote the growth of strawberry plants in a greenhouse when they suffer from insufficient solar radiation during the winter season. A TiO2 solution was sprayed on strawberry plants three times during the growth period. This treatment occurred once on the 5th day of each month from December to February at concentrations of 50, 100 or 150 mg·kg -1. The control strawberry plants were treated with a foliar solution lacking TiO2. The length of the petiole was inhibited by TiO2 treatments, especially those in January and February. In terms of the fruits, the TiO2 applications were found to increase the yield and hardness of strawberries compared to the control. In addition, the contents of chlorophyll a and b in the leaves of the strawberries were increased by the treatment with TiO2 foliar spray. In contrast, the phenolic compounds of the fruits were decreased as a result of the TiO2 treatments. Combined, our results reveal that the application of TiO2 can promote the yield and quality of strawberry plants sufferings from a shortage of sunlight in a plastic greenhouse during the winter season.

Genes for Fatty Acid Desaturases and Choline Oxidase are Responsible for Tolerance to Low-Temperature and Salinity Stresses in Cyanobacteria and Plants

Most cyanobacteria and plants contain high levels of polyunsaturated fatty acids of membrane lipids. We isolated the desA, desB and desC genes of Synechocystis sp. PCC 6803, which encode the Δ12, Δ15 (ω3) and Δ9 desaturases, respectively, of the acyl-lipid type. We disrupted the desA gene and the desD gene (for Δ6 desaturase) in Synechocystis sp. PCC 6803 by insertion of antibiotic resistance gene cartridges. These mutations greatly modified the extent of unsaturation of the fatty acids of membrane lipids. These changes in the unsaturation of membrane lipids altered the tolerance of cyanobacterial cells to low temperature. In higher plants, we isolated a cDNA for acyl-ACP: glycerol-3-phosphate acyltransferase from squash and introduced it into tobacco plants. The transformation modified the level of unsaturation of chloroplastic phosphatidylglycerol, and altered the tolerance of tobacco plants to low temperature. Glycinebetaine, a compatible solute, is synthesized in some halophilic plants. We cloned, from the soil bacterium Arthrobacter globiformis, the codA gene for choline oxidase which converts choline into glycinebetaine. introduced this gene into Synechococcus sp. PCC 7942, the resultant transformants accumulated glycinebetaine to some extent and became tolerant to salinity stresses.