Growth retardation and death of rice plants irradiated with carbon ion beams is preceded by very early dose- and time-dependent gene expression changes

The carbon-ion beam (CIB) generated by the heavy-ion medical accelerator in Chiba (HIMAC) was targeted to 7-day-old rice. Physiological parameters such as growth, and gene expression profiles were examined immediately after CIB irradiation. Dose-dependent growth suppression was seen three days post-irradiation (PI), and all the irradiated plants died by 15 days PI. Microarray (Agilent rice 22K) analysis of the plants immediately after irradiation (iai) revealed effects on gene expression at 270 Gy; 353 genes were up-regulated and 87 down-regulated. Exactly the same set of genes was affected at 90 Gy. Among the highly induced genes were genes involved in information storage and processing, cellular processes and signaling, and metabolism. RT-PCR analysis confirmed the microarray data.     

Production of in vitro haploid plants from in situ induced haploid embryos in winter squash (<Emphasis Type="Italic">Cucurbita maxima</Emphasis> Duchesne ex Lam.) via irradiated pollen

The influence of pollen irradiation on the production of in vitro haploid plants from in situ induced haploid embryos was investigated in winter squash (Cucurbita maxima Duchesne ex Lam.). Pollen were irradiated at different gamma-ray doses (50, 100, 200 and 300 Gray) and durations (9, 11, 15, 21, and 28 July). Production of in vitro haploid plantlets was influenced by irradiation dose, irradiation duration, genotype, and embryo type and embryo stage. Embryos were only obtained from lower irradiation doses (50 Gray and 100 Gray) and earlier irradiation durations (9, 11, and 15 July). The greatest embryo number per fruit was procured from “G14” and “55SI06” genotypes at 50 Gray gamma-ray dose. Necrotic embryos were higher than normal embryos at delayed harvest times (5 and 6 weeks after the pollination). The convenient harvest time for embryo rescue was observed about 4 weeks (between 25 and 30 days) after pollination. All cotyledon and amorphous embryos had only diploid plants while late-torpedo, arrow-tip, and pro-cotyledon embryos produced 33.3, 50.0, and 66.7% haploid plant. The frequency of haploid plantlets was 0.11, 1.17, 10.96 and 0.28 per 100 seeds, 100 embryos, 100 plantlets and a fruit at 50 Gray gamma-ray dose, respectively.     

Temporary effect of postharvest UV-C irradiation on gene expression profile in tomato fruit

To obtain an overall view on gene expression during the early stage (24 h) of tomato fruit in response to postharvest UV-C irradiation (4 kJ/m(2)), we performed a microarray analysis by using Affymetrix Tomato Genechip. The results showed that 274 and 403 genes were up- or down-regulated, respectively, more than two folds in postharvest tomato fruit irradiated with UV-C as compared with that in control fruit. The up-regulated genes mainly involve in signal transduction, defense response and metabolism. Conversely, genes related to cell wall disassembly, photosynthesis and lipid metabolism were generally down-regulated. These results opened ways to probe into the molecular mechanisms of the effects of postharvest UV-C irradiation on increased disease resistance, delayed softening, better quality maintenance and prolonged postharvest life in tomato fruit.     

An Arabidopsis mutant with enhanced resistance to powdery mildew.

We have identified an Arabidopsis mutant that displays enhanced disease resistance to the fungus Erysiphe cichoracearum, causal agent of powdery mildew. The edr1 mutant does not constitutively express the pathogenesis-related genes PR-1, BGL2, or PR-5 and thus differs from previously described disease-resistant mutants of Arabidopsis. E. cichoracearum conidia (asexual spores) germinated normally and formed extensive hyphae on edr1 plants, indicating that the initial stages of infection were not inhibited. Production of conidiophores on edr1 plants, however, was <16% of that observed on wild-type Arabidopsis. Reduction in sporulation correlated with a more rapid induction of defense responses. Autofluorescent compounds and callose accumulated in edr1 leaves 3 days after inoculation with E. cichoracearum, and dead mesophyll cells accumulated in edr1 leaves starting 5 days after inoculation. Macroscopic patches of dead cells appeared 6 days after inoculation. This resistance phenotype is similar to that conferred by "late-acting" powdery mildew resistance genes of wheat and barley. The edr1 mutation is recessive and maps to chromosome 1 between molecular markers ATEAT1 and NCC1. We speculate that the edr1 mutation derepresses multiple defense responses, making them more easily induced by virulent pathogens.     

Identification of genes responsive to gamma radiation in rat hepatocytes and rat liver by cDNA array gene expression analysis

The mechanisms underlying hepatocellular damage after irradiation are obscure. We identified genes induced by radiation in isolated rat hepatocytes in vitro by cDNA array gene expression analysis and then screened in vivo experiments with those same genes using real-time PCR and Western blotting. Hepatocytes were irradiated and cDNA array analyses were performed 6 h after irradiation. The mRNA of differentially expressed genes was quantitatively analyzed by real-time PCR. cDNA array analyses showed an up-regulation of 10 genes in hepatocytes 6 h after irradiation; this was confirmed by real-time PCR. In vivo, rat livers were irradiated selectively. Treated and sham-irradiated controls were killed humanely 1, 3, 6, 12, 24 and 48 h after irradiation. Liver RNA was analyzed by real-time PCR; expression of in vivo altered genes was also analyzed at the protein level by Western blotting. Up-regulation was confirmed for three of the in vitro altered genes (multidrug resistance protein, proteasome component C3, eukaryotic translation initiation factor 2). Histologically, livers from irradiated animals were characterized by steatosis of hepatocytes. Thus we identified genes that may be involved in liver steatosis after irradiation. The methods shown in this work should help to further clarify the consequences of radiation exposure in the liver.     

Selenium protects sorghum leaves from oxidative damage under high temperature stress by enhancing antioxidant defense system

Oxidative stress is commonly induced when plants are grown under high temperature (HT) stress conditions. Selenium often acts as an antioxidant in plants; however, its role under HT-induced oxidative stress is not definite. We hypothesize that selenium application can partly alleviate HT-induced oxidative stress and negative impacts of HT on physiology, growth and yield of grain sorghum [Sorghum bicolor (L.) Moench]. Objectives of this study were to investigate the effects of selenium on (a) leaf photosynthesis, membrane stability and antioxidant enzymes activity and (b) grain yield and yield components of grain sorghum plants grown under HT stress in controlled environments. Plants were grown under optimal temperature (OT; 32/22 °C daytime maximum/nighttime minimum) from sowing to 63 days after sowing (DAS). All plants were foliar sprayed with sodium selenate (75 mg L^?1) at 63 DAS, and HT stress (40/30 °C) was imposed from 65 DAS through maturity. Data on physiological, biochemical and yield traits were measured. High temperature stress decreased chlorophyll content, chlorophyll a fluorescence, photosynthetic rate and antioxidant enzyme activities and increased oxidant production and membrane damage. Decreased antioxidant defense under HT stress resulted in lower grain yield compared with OT. Application of selenium decreased membrane damage by enhancing antioxidant defense resulting in higher grain yield. The increase in antioxidant enzyme activities and decrease in reactive oxygen species (ROS) content by selenium was greater in HT than in OT. The present study suggests that selenium can play a protective role during HT stress by enhancing the antioxidant defense system.     

Identification of genes differentially expressed in husk tomato (<Emphasis Type="Italic">Physalis philadelphica</Emphasis>) in response to whitefly (<Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis>) infestation

Plants respond to phloem-feeding whiteflies by extensive changes in gene expression. To identify differentially expressed genes in husk tomato plants (Physalis philadelphica) infested with Trialeurodes vaporariorum, young plants were challenged with adult whiteflies, and forward and reverse subtractive libraries were constructed from infested leaves at 5 and 15 days after infestation. Several genes were identified as up-regulated; these included a diversity of genes involved in plant defense responses, protein synthesis or degradation, and cell wall fortification or modification. Genes required for amino acid biosynthesis, lipid metabolism and synthesis, including cell surface components such as suberin, responses to stress, photosynthesis and other functions, were similarly induced. Down-regulated genes were also identified, most prominently kinases and aquaporin genes. Similarities in defense responses between tomato and P. philadelphica were noted regarding the expression of certain genes in response to nematode, aphid, or whitefly. A role for abscisic acid, brassinosteroids, and cytokinins in the regulated response to whitefly infestation in P. philadelphica was also implied by the expression pattern of phytohormone-associated genes, including genes coding for proteins containing F-box motifs. Differential expression of selected genes was validated by quantitative real-time PCR. The possible role played by some of these genes during whitefly infestation is discussed.     

不同海拔地区(南京和拉萨)种植的甘蓝型油菜的种子基因差异表达

分别在南京(海拔8.9 m)和拉萨(海拔3 658 m)2个不同海拔地区种植甘蓝型油菜(Brassica napus)高油品系H105, 该材料含油量在两地分别为(46.04±1.42)%和(53.09±1.35)%。利用拟南芥表达谱基因芯片检测两地种植的H105开花后30天种子基因的表达。以种植在南京的H105为对照, 差异表达分析结果显示有421个差异表达的基因, 其中229个基因表达下调, 192个基因表达上调。这些基因按功能可初步分为代谢相关、运输相关、结合相关、转录相关、结构相关、发育相关、信号转导相关、其它相关及功能未知基因等几大类别。一些与光合成、糖代谢以及脂肪酸合成相关的重要基因, 如叶绿素a-b结合蛋白基因家族、蔗糖合酶、丙酮酸激酶、6-磷酸葡萄糖酸脱氢酶、ATP-柠檬酸裂解酶、柠檬酸合酶、异柠檬酸脱氢酶、脂肪酸去饱和酶(FAD6和FAD7)基因等被鉴定为差异表达。研究结果初步揭示了相关基因的表达变化规律, 为探讨油菜在不同海拔地区含油量差异的分子遗传机理提供了重要信息。     

Formation of short-wavelength chlorophyll(ide) after brief irradiation is correlated with the occurrence of protochlorophyll(ide)636–642 in dark-grown epi- and hypocotyls of bean (Phaseolus vulgaris)

Chlorophyll formation capacity along the seedling of bean ( Phaseolus vulgaris L. cv. Brede zonder draad) was investigated. After 7 days of irradiation a gradient was formed, where the primary leaf contained ca 300 times more chlorophyll per gram fresh weight than the lower hypocotyl section and ca 20 times more than the epicotyl. Similar chlorophyll gradients but at lower levels were seen when the seedlings were first placed in darkness for 7 days and then irradiated for 1, 2 or 7 days. Ultrastructural investigation of seedlings grown for 7 days in darkness and then irradiated for 24 h revealed a more developed inner membrane system with grana stacks in plastids of cells in the uppermost hypocotyl section compared to plastids of cells in lower hypocoty] sections. The higher up on the seedling the more the ratio increased of protochlorophyll(ide) emitting at 657 nm to short-wavelength protochlorophyll(ide). After flash irradiation of the different sections, fluorescence emission spectra with maxima at 680 and 690 nm, respectively, were observed, indicating the formation of short- and long wavelength chlorophyll(ide) forms. The lower the ratio of protochlorophyll(ide) emitting at 657 nm to the short-wavelength protochlorophyll(ide), the less long-wavelength chlorophyll(ide) was formed after irradiation. However, after continuous irradiation long-wavelength chlorophyll(ide) was formed. In dark grown roots, where only short-wavelength protochlorophyll forms were present, it was not possible to transform protochlorophyll to chlorophyll by flash irradiation. Possible explanations for this phenomenon are discussed.     

Expression pattern analysis of Will Die Slowly genes in Arabidopsis

Leaf senescence is a developmental programmed cell death (PCD) that occurs as a response to external and internal signals. Several factors, such as the environment, plant hormones, and senescence-associated genes, regulate leaf senescence. In Drosophila melanogaster, Will Die Slowly (WDS) is a WD-repeat protein, which is closely related to PCD. Phylogenetic analysis indicated that eight genes are highly homologous to D. melanogaster WDS (DmWDS) in Columbia ecotype (Col) of Arabidopsis thaliana. In this study, the expression patterns of three close homologues of DmWDS named WDS1, WDS2, and WDS3 were investigated. Real-time PCR revealed the spatio-temporal expression levels of these three genes. No tissue-specific expression of the three AtWDS genes was observed. These genes were expressed at every growth stage; the variation in their expression was similar: the expression of the three AtWDS reached the peak in leaves at the 37 days after sowing, at the time when the first pod initially appeared on the plant and the leaf 7 show 25 to 50% yellow; and the expression of the three AtWDS reached the peak in flowers at the 43.5 days after sowing, at the time when 50% of the flowers bloomed. In addition, the expression level of the three AtWDS peaked at the 48 h after the plants were treated with 0.5 mM salicylic acid (SA). WDS3 also exhibited a high expression at 24, 48, and 72 h. Taken together; these results suggest that AtWDS genes may be involved in plant PCD