The effect of endogenous mRNA levels on co-suppression in tomato

AbstractIntroduction of truncated polygalacturonase (PG) transgenes into tomato plants caused the production of small interfering RNAs (siRNAs) and co-suppression of both the endogenous and PG transgenes in ripening fruits by post-transcriptional gene silencing. In order to test the possible effect on co-suppression of the endogenous PG mRNA level, we transferred the PG transgenes from a PG-silenced line (wild type background) by crossing to two ripening regulatory mutants with reduced PG: Never-ripe (Nr, ∼10% endogenous PG mRNA compared to wild type) and ripening-inhibitor (rin, ∼1% endogenous PG mRNA) and to wild type (as a control). The PG transgenes caused strong co-suppression of the transgenes and the endogenous PG gene in cells with high PG mRNA background (wild type) and silencing appeared to be linked with higher transgene copy number and/or a particular transgene locus. In cells with low endogenous PG mRNA accumulation (Nr), the endogenous PG gene was preferentially suppressed compared to the transgenes, whose expression was not reduced significantly. The expression of the transgenes was also not reduced in the very low PG background (rin), in which endogenous PG was barely detectable. In all the analysed lines with all three PG background levels, siRNAs accumulated in leaves and green fruits, in which the endogenous PG gene is not transcribed. The relatively abundant production of siRNAs in most of the lines was linked with a particular transgene insert. These results suggest that a certain threshold level of endogenous PG mRNA is required for the co-suppression of the truncated PG transgenes and the endogenous PG gene or for extensive silencing of the transgenes

Effects of fully open-air [CO2] elevation on leaf photosynthesis and ultrastructure of Isatis indigotica Fort

Traditional Chinese medicine relies heavily on herbs, yet there is no information on how these herb plants would respond to climate change. In order to gain insight into such response, we studied the effect of elevated [CO2] on Isatis indigotica Fort, one of the most popular Chinese herb plants. The changes in leaf photosynthesis,chlorophyll fluorescence, leaf ultrastructure and biomass yield in response to elevated [CO2] (550619 mmol mol–1) were determined at the Free-Air Carbon dioxide Enrichment (FACE) experimental facility in North China. Photosynthetic ability of I. indigotica was improved under elevated [CO2]. Elevated [CO2] increased net photosynthetic rate (PN), water use efficiency (WUE) and maximum rate of electron transport (Jmax) of upper most fully-expended leaves, but not stomatal conductance (gs), transpiration ratio (Tr) and maximum velocity of carboxylation (Vc,max). Elevated [CO2] significantly increased leaf intrinsic efficiency of PSII (Fv’/Fm’) and quantum yield of PSII(WPSII), but decreased leaf non-photochemical quenching (NPQ), and did not affect leaf proportion of open PSII reaction centers (qP) and maximum quantum efficiency of PSII (Fv/Fm). The structural chloroplast membrane, grana layer and stroma thylakoid membranes were intact under elevated [CO2], though more starch grains were accumulated within the chloroplasts than that of under ambient [CO2]. While the yield of I. indigotica was higher due to the improved photosynthesis under elevated [CO2], the content of adenosine, one of the functional ingredients in indigowoad root was not affected

Induction of defensive enzymes (isozymes) during defense against two different fungal pathogens in pear calli

Activities of defensive enzymes peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), polyphenol oxidase (PPO) and esterase (EST) and their isozymes in pear calli were studied to reveal their role in the defensive response to different fungal infections and to find some clues to enhance their antimicrobial properties. The results confirm the fact that the activities and isozymes of these five enzymes showed differences in response to different fungal infections. After the inoculation of two different fungi for the same calli, its defensive enzymes’ activities changed relatively when compared with those of the control and in Botryosphaeria berengriana f.sp. piricola (BBP)-infected calli, the enzymes’ activities changed more significantly than those of Monilinia fructigena Honcy (MFH). Meanwhile, more new isozymes were induced by BBP infection. These are in agreement with the fact that the BBP-infected calli decay was slower than that of the MFH. These results suggest that enhancing defensive enzymes’ activities and inducing new isozymes may be related to mitigating pathogen-induced oxidative damage which result in the decrease of calli decay, and this implies that antioxidant defense response may be involved in the mechanisms of plant against fungal pathogen.Keywords: Pear callus, fungi infection, defense enzyme, isozyme, biochemical defense mechanis

A Larger Root System Is Coupled With Contrasting Expression Patterns of Phosphate and Nitrate Transporters in Foxtail Millet [Setaria italica (L.) Beauv.] Under Phosphate Limitation

Foxtail millet [Setaria italica (L.) Beauv.], a widely cultivated food and fodder crop, develops a smaller root system while enlarges the root diameter facilitating nutrient transport under nitrogen limitation. How foxtail millet responds to phosphate limitation (LP) remains unaddressed. LP seedlings of the sequenced variety Yugu1 had significantly lower P concentrations in both shoots and roots and displayed higher levels of anthocyanin accumulation in leaves, indicating that the seedlings suffered from P limitation under hydroponic culture. One obvious and adaptive phenotype of LP plants was the larger root system mostly as the result of stimulation of lateral root proliferation in terms of the number, density, and length. Preferential biomass accumulation in the root under LP ensured carbon provision for root expansion and resulted in significant increases in the total and specific root length, which substantially extended the absorptive surface of P in the growth medium. Elevation of auxin and gibberellin concentrations might serve as an internal boost underpinning root architectural re-patterning under LP. Not just morphological adaptation, up-regulation of expression of SiPHT1;1 and SiPHT1;4 in roots and that of SiPHT1;2 in roots and shoots preconditioned adaptive enhancement of P uptake and translocation under LP. Interestingly, internal nitrogen surpluses occurred as indicated by dramatic increases in free amino acids in LP shoots and roots and higher concentrations of nitrogen in roots. Such nitrogen surplus ‘signals’ tended to switch down expression of nitrate transporters SiNRT2.1 and SiNAR2.1 in the root and that of SiNRT1.11 and SiNRT1.12 in the shoot to reduce nitrate mobilization toward or within the shoot. Together, our work provided new insights into adaption of a critical cereal crop to LP and its innate connection with nitrogen nutrition

Characterization of volatile aroma compounds after in-vial cooking of foxtail millet porridge with gas chromatography-mass spectrometry

Foxtail millet has become popular over recent years for its nutritional value and ecological functions. The aroma of foxtail millet is not well characterized, which is critical for its eating quality and understanding the biochemistry and genetics of aroma is important for molecular breeding of millets rich in aroma. In this study, the volatile aroma compounds of the elite millet variety Jingu 21 were investigated at different cooking times, pH, processing methods, and compared with 3 other varieties. An in-vial cooking method was developed which combined solid phase micro-extraction and gas chromatography-mass spectrometry for the detection and identification of volatile compounds. The main findings were: a) Twelve aroma compounds were identified during cooking, which were hexanal, heptanal, octanal, (E)-2-heptenal, nonanal, trans-2-octenal, trans-2-nonenal, 2,4-nonadienal, (E,E)-2,4-decadienal, 1-octen-3-ol, 2-pentylfuran and 6-methyl-5- hepten-2-one. b) Longer cooking times produced higher concentrations of aroma compounds. c) Variations in cooking pH (from 6 to 8) had no obvious impact on the aroma of the millet porridge. d) More volatile compounds were released from millet flour compared to millet grain. e) There were significant differences among varieties and Jingu 21 millet showed the highest abundance of most aroma compounds, explaining partly why it is strongly favored by consumers for decades

Characterization of volatile aroma compounds after in-vial cooking of foxtail millet porridge with gas chromatography-mass spectrometry

Foxtail millet has become popular over recent years for its nutritional value and ecological functions. The aroma of foxtail millet is not well characterized, which is critical for its eating quality and understanding the biochemistry and genetics of aroma is important for molecular breeding of millets rich in aroma. In this study, the volatile aroma compounds of the elite millet variety Jingu 21 were investigated at different cooking times, pH, processing methods, and compared with 3 other varieties. An in-vial cooking method was developed which combined solid phase micro-extraction and gas chromatography-mass spectrometry for the detection and identification of volatile compounds. The main findings were: a) Twelve aroma compounds were identified during cooking, which were hexanal, heptanal, octanal, (E)-2-heptenal, nonanal, trans-2-octenal, trans-2-nonenal, 2,4-nonadienal, (E,E)-2,4-decadienal, 1-octen-3-ol, 2-pentylfuran and 6-methyl-5- hepten-2-one. b) Longer cooking times produced higher concentrations of aroma compounds. c) Variations in cooking pH (from 6 to 8) had no obvious impact on the aroma of the millet porridge. d) More volatile compounds were released from millet flour compared to millet grain. e) There were significant differences among varieties and Jingu 21 millet showed the highest abundance of most aroma compounds, explaining partly why it is strongly favored by consumers for decades

Molecular analysis of post-harvest physiological deterioration of cassava

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN037096 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

The Integration of Genome-Wide Association Study and Homology Analysis to Explore the Genomic Regions and Candidate Genes for Panicle-Related Traits in Foxtail Millet

Panicle traits are important factors affecting yield, and their improvement has long been a critical goal in foxtail millet breeding. In order to understand the genetic basis of panicle formation, a large-scale genome-wide association study (GWAS) was performed in this study for six panicle-related traits based on 706,646 high-polymorphism SNP loci in 407 accessions. As a result, 87 quantitative trait loci (QTL) regions with a physical distance of less than 100 kb were detected to be associated with these traits in three environments. Among them, 27 core regions were stably detected in at least two environments. Based on rice–foxtail millet homologous comparison, expression, and haplotype analysis, 27 high-confidence candidate genes in the QTL regions, such as Si3g11200 (OsDER1), Si1g27910 (OsMADS6), Si7g27560 (GS5), etc., affected panicle-related traits by involving multiple plant growth regulator pathways, a photoperiod response, as well as panicle and grain development. Most of these genes showed multiple effects on different panicle-related traits, such as Si3g11200 affecting all six traits. In summary, this study clarified a strategy based on the integration of GWAS, a homologous comparison, and haplotype analysis to discover the genomic regions and candidate genes for important traits in foxtail millet. The detected QTL regions and candidate genes could be further used for gene clone and marker-assisted selection in foxtail millet breeding