Poly(amic acid)s (PAAs) alignment agents have been prepared from the alicyclic dianhydrides, including 1,2,3,4‐cyclobutanetetracarboxylic dianhydride (CBDA, I), ...1,3‐dimethyl‐1,2,3,4‐cyclobutanetetracarboxylic dianhydride (DMCBDA, II), and ester‐linked aromatic diamines, including 4‐aminophenyl‐4′‐aminobenzoate (APAB, a) and bis(4‐aminophenyl)terephthalate (BPTP, b), respectively. The derived PAAs, including PAA‐Ia (CBDA‐APAB), PAA‐Ib (CBDA‐BPTP), and PAA‐IIa (DMCBDA‐APAB) exhibited the preferable molecular weights, while the PAA‐IIb (DMCBDA‐BPTP) showed the low one due to the low polymerization reactivity both for the DMCBDA dianhydride and the BPTP diamine. All the PAA solutions except PAA‐IIb were adopted as the alignment components to fabricate liquid crystal (LC) minicells with a mode of in‐plane switching (IPS). The polyimides (PI) alignment layers derived from the thermal dehydration reaction of the PAA precursors at 230°C for 30 min showed good alignments effects to the LC molecules, which exhibited the pretilt angles (θp) from 0.09 to 0.15° after being exposed by the linear polarized ultraviolet light sources with the wavelength of 254 nm. In addition, the PI alignment layers afforded good optoelectronic features to the minicells, including the voltage holding ratio values over 97% at room temperature, and the residual direct circuit voltages lower than 1.0 V. The anchoring energy results indicated that the PI‐IIa (DMCBDA‐APAB) alignment layer showed the highest interaction with the LC molecules, and thus exhibited the highest threshold voltage (Vth) in the voltage‐transmittance (V‐T) measurements for the minicells.
DNA methylation plays an important role in plant growth and development, and in regulating the activity of transposable elements (TEs). Research on DNA methylation-related (DMR) genes has been ...reported in Arabidopsis, but little research on DMR genes has been reported in Brassica rapa and Brassica oleracea, the genomes of which exhibit significant differences in TE content. In this study, we identified 78 and 77 DMR genes in Brassica rapa and Brassica oleracea, respectively. Detailed analysis revealed that the numbers of DMR genes in different DMR pathways varied in B. rapa and B. oleracea. The evolutionary selection pressure of DMR genes in B. rapa and B. oleracea was compared, and the DMR genes showed differential evolution between these two species. The nucleotide diversity (π) and selective sweep (Tajima's D) revealed footprints of selection in the B. rapa and B. oleracea populations. Transcriptome analysis showed that most DMR genes exhibited similar expression characteristics in B. rapa and B. oleracea. This study dissects the evolutionary differences and genetic variations of the DMR genes in B. rapa and B. oleracea, and will provide valuable resources for future research on the divergent evolution of DNA methylation between B. rapa and B. oleracea.
An endoplasmic reticulum-localized tomato omega-3 fatty acid desaturase gene (
LeFAD3) was isolated and characterized with regard to its sequence, response to various temperatures and function in ...transgenic tomato plants. Northern blot analysis showed that
LeFAD3 was expressed in all organs tested and was markedly abundant in roots. Meanwhile, the expression of
LeFAD3 was induced by chilling stress (4 °C), but inhibited by high temperature (40 °C). The transgenic plants were obtained under the control of the cauliflower mosaic virus 35S promoter (35S-CaMV). Northern and western blot analyses confirmed that sense
LeFAD3 was transferred into tomato genome and overexpressed. Level of linolenic acids (18:3) increased and correspondingly level of linoleic acid (18:2) decreased in leaves and roots. After chilling stress, the fresh weight of the aerial parts of transgenic plants was higher than that of the wild type (WT) plants, and the membrane system ultrastructure of chloroplast in leaf cell and all the subcellular organelles in root tips of transgenic plants kept more intact than those of WT. Relative electric conductivity increased less in transgenic plants than that in WT, and the respiration rate of the transgenic plants was notably higher than that of WT. The maximal photochemical efficiency of PSII (
F
v/
F
m) and the O
2 evolution rate in WT decreased more than those in transgenic plants under chilling stress. Together with other data, results showed that the overexpression of
LeFAD3 led to increased level of 18:3 and alleviated the injuries under chilling stress.
An endoplasmic reticulum-localized tomato ω-3 fatty acid desaturase gene （LeFAD3） was isolated. The antisense tomato plants were obtained under the control of the cauliflower mosaic virus 35S ...promoter （35S-CaMV）. Northern blot analysis confirmed that the expression of LeFAD3 was inhibited in the tomato genome. Levels of 18：3 decreased and correspondingly levels of 18：2 increased in total lipids of leaves and roots. After heat stress, the fresh weight of the aerial parts of antisense transgenic plants was higher than that of the wild type （WT） plants. The membrane system ultrastructure of chloroplasts in leaf cells and all of the subcellular organelles in the root tips of transgenic plants remained more intact than those of WT. Relative electric conductivity increased less in transgenic plants than in WT. Under heat stress, the maximal photochemical efficiency of photosystem Ⅱ （Fv/Fm） and the O2 evolution rate decreased more in WT than in transgenic plants. These results suggested that the depletion of LeFAD3 increased the saturation of fatty acids and alleviated high temperature stress.
GDP-mannose pyrophosphorylase (GMPase: EC 2.7.7.22) plays a crucial role in the synthesis of
l
-ascorbate (AsA) and the consequent detoxification of reactive oxygen species (ROS). Herein, a
GMPase
...(accession ID DQ449030) was identified and cloned from tomato. The full-length cDNA sequence of this gene contains 1,498 bp nucleotides encoding a putative protein with 361 amino acid residues of approximate molecular weight 43 kDa. Northern blot analysis revealed that the
GMPase
was expressed in all examined tomato tissues, but its expression level was up-regulated in tomato plants subjected to abnormal temperatures. We then overexpressed this tomato
GMPase
in tobacco plants and observed that the activity of GMPase and the content of AsA were significantly increased by two- to fourfold in the leaves of transgenic tobacco plants. The effect of this gene overexpression was superimposed by the treatments of high or low temperature in tobacco, since the activities of both chloroplastic SOD (superoxide dismutase EC 1.15.1.1), APX (ascorbate peroxidase EC 1.11.1.7) and the content of AsA in leaves were significantly higher in transgenic plants than those of WT, while the contents of H
2
O
2
and O
2
−·
were reduced. Meanwhile, relative electric conductivity increased less in transgenic plants than that in WT, and the net photosynthetic rate (
P
n
) and the maximal photochemical efficiency of PSII (
F
v
/
F
m
) of transgenic plants were notably higher than those of WT under temperature stresses. In conclusion, the overexpression of
GMPase
increased the content of AsA, thereby leading to the increase in tolerance to temperature stress in transgenic plants.
Silicon (Si) is known to be beneficial to plants in alleviating biotic and abiotic stresses. However, its uptake from soil and transport in plants is not well documented. In this work, we cloned two ...cucumber putative silicon transporter genes (
CSiT
-
1
and
CSiT
-
2
) and characterized some of their functions in cucumber plants. The proteins coded by these two genes were almost identical to other plant Si influx transporters, containing two conserved NPAs (asparagine proline alanine) and four ar/R (aromatic/arginine) selectivity filter-forming residues G(Gly)/C(Cys), S(Ser), G(Gly), and R(Arg). The two genes were expressed in all tissues and most interestingly the diurnal patterns of their expression were displaying a circadian rhythm. Compared with rice
OsLsi1
or other plant Si transport genes, these two genes were highly expressed in leaves and their expression levels corresponded to Si supply in the hydroponic culture solution. Both CSiT-1 and CSiT-2 proteins were localized in the plasma membrane when they were heterogeneously expressed in tobacco leaves. Our data suggested that the two genes cloned from cucumber were likely coding silicon transporters and had a distinct diurnal expression pattern of a circadian rhythm both in leaves and roots.
KEY MESSAGE : Transgenic tomato plants overexpressing LeFAD3 sense and antisense sequences were generated. Salt stress suppressed the growth of WT and antisense plants to a higher extent than that in ...sense plants. In this study, we investigated the role of the LeFAD3-encoding ER-type omega-3 fatty acid desaturase in salt tolerance in tomato plants. We created transgenic tomato plants by overexpressing its sense and antisense sequences under the control of the cauliflower mosaic virus 35S promoter. Based on the results of northern and western blotting as well as quantitative reverse transcription-polymerase chain reaction, sense plants expressed more desaturase than wild-type (WT) plants, whereas antisense plants expressed less desaturase than WT. Salt stress suppressed the growth of both WT and antisense plants to a higher extent than that in sense plants, which can be attributed to the fact that sense plants performed better in maintaining the integrity of the membrane system, as revealed by electron microscopy. The concomitant increase in superoxide dismutase (EC 1.15.1.1) and ascorbate peroxidase (EC 1.11.1.7) may have alleviated the photoinhibition caused by the increased level of ROS in sense plants. Our results suggest that LeFAD3 overexpression can enhance the tolerance of early seedlings to salinity stress.
Polyimide (PI) has been widely used as the alignment layers for twisted-nematic (TN) thin film transistor driven liquid crystal display devices (TFT-LCDs). However, the currently PI alignment layers ...based on 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and common aromatic diamines usually showed low alignment abilities to rigid-rod liquid crystal (LC) molecule with low pretilt angles. Thus, in the current work, a series of novel PI precursors, poly(amic acid)s (PAAs) alignment agents were developed. For this purpose, four PAAs have been prepared from a newly developed ester-linked aromatic diamine containing
tert
-butyl-substituted cyclohexyl in the side chain, 4'-
tert
-butyl-cyclohexyl-3,5-diaminobenzoate (DABC) and various dianhydrides. The PAAs included three ones derived from aliphatic or alicyclic dianhydrides, including PAA-1 (BDA-DABC) from 1,2,3,4-butanetetracarboxylic dianhydride (BDA), PAA-2 (CBDA-DABC) from CBDA, and PAA-3 (DMCBDA-DABC) from 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride (DMCBDA), and one from aromatic dianhydride, 2,2′-bis(3,4-dicarboxylphenyl)hexafluoropropane dianhydride (6FDA) (PAA-4, 6FDA-DABC). The derived PAAs were used as the alignment agents to fabricate the minicells of twisted-nematic (TN) modes of thin-film transistor driven liquid crystal display (TFT-LCDs). The PI alignment layers obtained by the thermal imidization of the corresponding PAAs, followed by rubbing treatments showed good alignment ability to the liquid crystal (LC) molecules with the pretilt angles (
θ
p
) in the range of 1.46 ~ 7.02°. PI-3 (DMCBDA-DABC) showed the highest
θ
p
of 7.02°, while PI-4 (6FDA-DABC) exhibited the lowest one of 1.46°. The semi-aromatic PI-1 ~ PI-3 layers showed higher optical transmittance than that of the wholly aromatic PI-4 counterpart. PI-4 layer exhibited the lowest voltage holding ratio (VHR) of 91.32% at 60 °C, which was apparently lower than those of the semi-aromatic PI-1 ~ PI-3 counterparts (> 96.00%). In addition, the semi-alicyclic PI alignment layers (PI-2 and PI-3) showed lower residual direct circuit voltages (RDC) than that of the wholly aromatic PI-4. At last, the photoalignment behaviors of the PI alignment layers were preliminarily investigated. Only PI-2 and PI-3 exhibited the alignment ability to the LC molecules after being treated with the linear polarized ultraviolet (LPUV) with the wavelength of 254 nm.
In our previous work
1
we investigated the role of tomato GDP-mannose pyrophosphorylase (EC 2.7.7.22) in plants by overexpressing its gene in tobacco leaves and showed its function in AsA ...metabolism and detoxification of reactive oxygen species under temperature stresses. In this study, we use the antisense technique to block the endogenous GMPase gene expression in tobacco in order to further investigate its function. Northern and western blot analysis confirmed that the expression of endogenous tobacco GMPase mRNA and protein was inhibited by this antisense expression. Consequently, the activity of GMPase and the content of AsA in the leaves of antisense transgenic plants were markedly decreased. This was also the case for the activities of both chloroplastic SOD (superoxide dismutase EC 1.15.1.1), APX (ascorbate peroxidase EC 1.11.1.7) and the content of AsA in leaves of the transgenic plants. On the contrary, the contents of H
2
O
2
and O
2
−•
were increased. Meanwhile, the net photosynthetic rate (
Pn
) and the maximal photochemical efficiency of PSII (
Fv/Fm
) also declined in the leaves of antisense plants. Under high or low temperature stresses, the seed germination rate of the antisense transgenic plants was significantly decreased in comparison with that of the wild-type tobacco. Interestingly, the antisense plants had smaller leaves and an earlier onset of flowering. In conclusion, the depletion of GMPase decreased the content of AsA, resulting in the plants susceptible to the oxidative damage caused by temperature stresses and subjected to developmental alternations.
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