Search

Dehydration-responsive element binding proteins (DREBs) constitute a large subfamily in the plant-specific APETALA2/ethylene-responsive factor (ERF) family and play crucial roles in plant stress tolerance. So far, studies on the A-5 subgroup DREBs which comprise the largest proportion of the DREB subfamily are limited. Here, we report functional characterization of two A-5 subgroup genes named AmDREB1 and AmDREB2 from Ammopiptanthus mongolicus, a desert shrub with high abiotic stress tolerance. Both AmDREB1 and AmDREB2 proteins contain an ERF-associated amphiphilic repression (EAR)-like motif and were localized in the nucleus. The transcription levels of AmDREB1 and AmDREB2 in laboratory-cultured seedlings increased differentially under dehydration, salt, cold and/or heat stresses as well as under abscisic acid (ABA) treatment. In leaves of naturally growing shrubs in the wild, the transcription level of AmDREB2 also increased in response to seasonal cold weather of a year. Moreover, AmDREB1 was most abundantly expressed in leaves, followed by immature pods; AmDREB2 was abundantly expressed in all examined organs. Constitutively expressing AmDREB1 in Arabidopsis significantly enhanced drought and salt tolerances of transgenic lines, likely by inducing the expression of some stress-inducible genes and accumulating more proline and less Na+. Constitutive expression of AmDREB2 conferred only osmotic stress tolerance in transgenic Arabidopsis at the seed germination stage. Both AmDREBs also conferred ABA insensitivity in transgenics. This study provides important evidence that the A-5 subgroup EAR motif-containing DREBs can positively regulate stress response and tolerance in plants, and that AmDREB1 may have potential application in improving drought and salt tolerances in crop plants. AmDREB1 and AmDREB2 were differentially induced by abiotic stressors, exogenous ABA and seasonal cold weather. The tolerances of their transgenics to drought and/or salt as well as ABA were enhanced.

The

Chloroplast glycerol-3-phosphate acyltransferase (GPAT) is the first key enzyme determining the unsaturation of phosphatidylglycerol (PG) in thylakoid membranes and is involved in the tolerance of plants to chilling, heat and high salinity. However, whether the GPAT affects plant tolerance to other stressors has been scarcely reported. Ammopiptanthus mongolicus is the only evergreen broadleaf shrub growing in the central Asian desert, and it has a high tolerance to harsh environments, especially extreme cold. This study aimed to characterize the physiological function of AmGPAT from A. mongolicus. The transcription of AmGPAT was markedly induced by cold and drought but differentially suppressed by heat and high salinity in the laboratory-cultured seedlings. The gene also had the highest transcription levels in the leaves of shrubs naturally growing in the wild during the late autumn and winter months throughout the year. Moreover, AmGPAT was most abundantly expressed in leaves and immature pods rather than other organs of the shrubs. Constitutive expression of AmGPAT in Arabidopsis increased the levels of cis-unsaturated fatty acids, especially that of linolenic acid (18:3), mainly in PG but also in other chloroplast lipids in transgenic lines. More importantly, the transgene significantly increased the tolerance of the transgenics not only to chilling but also to freezing and oxidative stress at both the cellular and whole-plant levels. In contrast, this gene reduced heat tolerance of the transgenic plants. This study improves the current understanding of chloroplast GPAT in plant tolerance against abiotic stressors through regulating the unsaturation of chloroplast lipids, mainly that of PG.

Dehydration-responsive element-binding (DREB) transcription factors (TFs) play a vital role in plant response to abiotic stresses. However, little is known about DREB TFs in plants adapted to harsh environments and in the formation of polyunsaturated fatty acids (PUFAs), a major membrane component closely associated with plant stress tolerance. Here, we characterized AmDREB2C in Ammopiptanthus mongolicus (Maxim. ex kom.) Cheng F., a desert evergreen broadleaf shrub with a high tolerance to harsh environments. AmDREB2C encodes a canonical DREB2-type TF, and the protein was localized in the nucleus. AmDREB2C had the highest expression levels in leaves of naturally growing shrubs in the wild during the winter season of a year of sampling. The expression was also induced by cold, heat and drought stresses in laboratory-cultured seedlings. Moreover, AmDREB2C was most abundantly expressed in young leaves and immature seeds rather than other tissues of the shrubs. Constitutive expression of AmDREB2C in Arabidopsis enhanced freezing, heat and drought tolerances of the transgenic plants, likely through inducing the expression of important stress-responsive genes. The transgene also increased the level of linolenic acid (C18:3), a major PUFA in most plant species, in leaves and seeds of the transgenic plants. Correspondingly, the transcription of FAD3, FAD7 and FAD8, three genes encoding fatty acid desaturases (FADs) responsible for the production of C18:3, showed a differential up-regulation in these two organs. This study provides new insight into the underlying molecular mechanisms of A. mongolicus' ability to endure harsh environments and DREB TF regulation of fatty acid desaturation.

Drought and cold are the primary factors limiting plant growth worldwide. The Ammopiptanthus mongolicus NAC11 (AmNAC11) gene encodes a stress-responsive transcription factor. Expression of the AmNAC11 gene was induced by drought, cold and high salinity. The AmNAC11 protein was localized in the nucleus and plays an important role in tolerance to drought, cold and salt stresses. We also found that differential expression of AmNAC11 was induced in the early stages of seed germination and was related to root growth. When the AmNAC11 gene was introduced into Arabidopsis thaliana by an Agrobacterium-mediated method, the transgenic lines expressing AmNAC11 displayed significantly enhanced tolerance to drought and freezing stresses compared to wild-type Arabidopsis thaliana plants. These results indicated that over-expression of the AmNAC11 gene in Arabidopsis could significantly enhance its tolerance to drought and freezing stresses. Our study provides a promising approach to improve the tolerance of crop cultivars to abiotic stresses through genetic engineering.

Dehydration-responsive element-binding (DREB) transcription factors (TFs) are key regulators of stress-inducible gene expression in plants. Anthocyanins, an important class of flavonoids, protect plants from reactive oxygen species produced under abiotic stresses. However, regulation of DREBs on anthocyanin accumulation is largely unknown. Here, an A-5 subgroup DREB gene (AmDREB3) isolated from Ammopiptanthus mongolicus, a desert broadleaf shrub with very high tolerance to harsh environments, was characterized in terms of both abiotic stress tolerance and anthocyanin accumulation. AmDREB3 does not contain the transcriptional repression motif EAR, and the protein was located in the nucleus and has transcriptional activation capacity. The transcription of AmDREB3 was differentially induced in the shoots and roots of A. mongolicus seedlings under drought, salt, heat, cold, ultraviolet B, and abscisic acid treatments. Moreover, the transcript levels in twigs, young leaves, and roots were higher than in other organs of A. mongolicus shrubs. Constitutively expressing AmDREB3 improved the tolerance of transgenic Arabidopsis to drought, high salinity and heat, likely by inducing the expression of certain stress-inducible genes. The transgenic Arabidopsis seedlings also exhibited an obvious purple coloration and significant increases in anthocyanin accumulation and/or oxidative stress tolerance under drought, salt, and heat stresses. These results suggest that the AmDREB3 TF may be an important positive regulator of both stress tolerance and anthocyanin accumulation.

Cellular specialization in abiotic stress responses is an important regulatory feature driving plant acclimation. Our in silico approach of iterative coexpression, interaction, and enrichment analyses predicted root cell-specific regulators of phosphate starvation response networks in Arabidopsis (Arabidopsis thaliana). This included three uncharacterized genes termed Phosphate starvation-induced gene interacting Root Cell Enriched (PRCE1, PRCE2, and PRCE3). Root cell-specific enrichment of 12 candidates was confirmed in promoter-GFP lines. T-DNA insertion lines of 11 genes showed changes in phosphate status and growth responses to phosphate availability compared with the wild type. Some mutants (cbl1, cipk2, prce3, and wdd1) displayed strong biomass gain irrespective of phosphate supply, while others (cipk14, mfs1, prce1, prce2, and s6k2) were able to sustain growth under low phosphate supply better than the wild type. Notably, root or shoot phosphate accumulation did not strictly correlate with organ growth. Mutant response patterns markedly differed from those of master regulators of phosphate homeostasis, PHOSPHATE STARVATION RESPONSE1 (PHR1) and PHOSPHATE2 (PHO2), demonstrating that negative growth responses in the latter can be overcome when cell-specific regulators are targeted. RNA sequencing analysis highlighted the transcriptomic plasticity in these mutants and revealed PHR1-dependent and -independent regulatory circuits with gene coexpression profiles that were highly correlated to the quantified physiological traits. The results demonstrate how in silico prediction of cell-specific, stress-responsive genes uncovers key regulators and how their manipulation can have positive impacts on plant growth under abiotic stress.

Phosphorus is an essential macro element for plant growth and development. PHO1 is an important factor for phosphorus transportation from underground to aboveground parts. Different from Arabidopsis , rice PHO1 has a natural cis -antisense transcript. To clarify whether PHO1 antisense transcript plays a role in plant response to phosphorus stress, the antisense transcript of PHO1-2 was cloned and its response to P deficiency was analyzed. Transgenic plants with overexpression of the PHO1 antisense transcript were obtained. The results of phosphorus content measurement showed significantly lower phosphorus content in leaves of transgenic seedlings than that of the wild type, but the phosphorus content in the root of overexpression transgenic lines was higher than that of the wild type. This result was in consistent with the phenotype of PHO1 loss of function material. Quantitative RT-PCR results showed that the transcript level of PHO1 was significantly lowered in the antisense transcript overexpression transgenic lines. The results suggested that PHO1 antisense transcripts were involved in phosphorus homeostasis regulation by regulating the transcript level of PHO1 .

The present study aimed at providing a new method in sight into short-wavelength near-infrared (NIR) spectroscopy of in pharmaceutical quantitative analysis. To do that, 124 experimental samples of metronidazole powder were analyzed using artificial neural networks (ANNs) in the 780–1100 nm region of short-wavelength NIR spectra. In this paper, metronidazole was as active component and other two components (magnesium stearate and starch) were as excipients. Different preprocessing spectral data (first-derivative, second-derivative, standard normal variate (SNV) and multiplicative scatter correction (MSC)) were applied to establish the ANNs models of metronidazole powder. The degree of approximation, a new evaluation criterion of the networks was employed to prove the accuracy of the predicted results. The results presented here demonstrate that the short-wavelength NIR region is promising for the fast and reliable determination of major component in pharmaceutical analysis.