BackgroundPotassium (K+) is an important nutrient ion in plant cells and plays crucial roles in many plant physiological and developmental processes. In the natural environment, K+ deficiency is a common abiotic stress that inhibits plant growth and reduces crop productivity. Several microarray studies have been conducted on genome-wide gene expression profiles of rice during its responses to various stresses. However, little is known about the transcriptional changes in rice genes under low-K+ conditions.ResultsWe analyzed the transcriptomic profiles of rice roots in response to low-K+ stress. The roots of rice seedlings with or without low-K+ treatment were harvested after 6 h, and 3 and 5 d, and used for microarray analysis. The microarray data showed that many genes (2,896) were up-regulated or down-regulated more than 1.2-fold during low-K+ treatment. GO analysis indicated that the genes showing transcriptional changes were mainly in the following categories: metabolic process, membrane, cation binding, kinase activity, transport, and so on. We conducted a comparative analysis of transcriptomic changes between Arabidopsis and rice under low-K+ stress. Generally, the genes showing changes in transcription in rice and Arabidopsis in response to low-K+ stress displayed similar GO distribution patterns. However, there were more genes related to stress responses and development in Arabidopsis than in rice. Many auxin-related genes responded to K+ deficiency in rice, whereas jasmonic acid-related enzymes may play more important roles in K+ nutrient signaling in Arabidopsis.ConclusionsAccording to the microarray data, fewer rice genes showed transcriptional changes in response to K+ deficiency than to phosphorus (P) or nitrogen (N) deficiency. Thus, transcriptional regulation is probably more important in responses to low-P and -N stress than to low-K+ stress. However, many genes in some categories (protein kinase and ion transporter families) were markedly up-regulated, suggesting that they play important roles during K+ deficiency. Comparative analysis of transcriptomic changes between Arabidopsis and rice showed that monocots and dicots share many similar mechanisms in response to K+ deficiency, despite some differences. Further research is required to clarify the differences in transcriptional regulation between monocots and dicots.

Potassium (K + ) plays crucial roles in plant growth and development. In natural environments, K + availability in soils is relatively low and fluctuating. Transcriptional regulation of K + transporter genes is one of the most important mechanisms in the plant's response to K + deficiency. In this study, we demonstrated that the transcription factor ARF2 (Auxin Response Factor 2) modulates the expression of the K + transporter gene HAK5 (High Affinity K + transporter 5) in Arabidopsis thaliana. The arf2 mutant plants showed a tolerant phenotype similar to the HAK5-overexpressing lines on low-K + medium, whose primary root lengths were longer than those of wild-type plants. High-affinity K + uptake was significantly increased in these plants. ARF2-overexpressing lines and the hak5 mutant were both sensitive to low-K + stress. Disruption of HAK5 in the arf2 mutant abolished the low-K + -tolerant phenotype of arf2. As a transcriptional repressor, ARF2 directly bound to the HAK5 promoter and repressed HAK5 expression under K + sufficient conditions. ARF2 can be phosphorylated after low-K + treatment, which abolished its DNA binding activity to the HAK5 promoter and relieved the inhibition on HAK5 transcription. Therefore, HAK5 transcript could be induced, and HAK5-mediated high-affinity K + uptake was enhanced under K + deficient conditions. The presented results demonstrate that ARF2 plays important roles in the response to external K + supply in Arabidopsis and regulates HAK5 transcription accordingly.

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This study mainly investigated the composition of adult male Chinese mitten crab () from four grades/sizes (Grade I: 200-249 g; Grade II: 175-199 g; Grade III: 150-174 g; Grade IV: ≤ 150 g). The results showed that the grade III crabs had the largest gonadsomatic index (GSI), which was significantly higher than the grade I and grade II crabs, no significant difference was found with the grade IV crab. Significant differences in moisture and total lipid contents were observed among various edible parts from different grades of male . In particular, grade II crabs had the highest total lipid and dry matter content for hepatopancreas. A balanced amino acids composition and a high essential amino acids score (EAAS) were found in the muscle and gonads of grade III crabs. The levels of poly-unsaturated fatty acids (PUFA), n-3 PUFA, n-6 PUFA and docosahexaenoic acid (DHA) in the hepatopancreas, as well as the contents of PUFA, highly-unsaturated fatty acids (HUFA), n-3 PUFA, arachidonic acid (ARA), and eicosapentaenoic acid (EPA) in the gonads were significantly increased in the grade II crabs. Taken together, it can generally be concluded that adult male of 150-200 g (Grade II-III) weight have the highest nutritional quality even though they are not the largest crabs.

Combining the chemistry of metal−organic frameworks (MOFs) and covalent organic frameworks (COFs) can bring new opportunities for the design of advanced materials with enhanced tunability and functionality. Herein, we constructed two COFs based on Ni−bis(dithiolene) units and imine bonds, representing a bridge between traditional MOFs and COFs. The Ni− bis(dithiolene)tetrabenzaldehyde as the 4-connected linker was initially synthesized, which was further linked by 4-connected tetra(aminophenyl)pyrene (TAP) or 3connected tris(aminophenyl)amine (TAA) linkers into two COFs, namely, Ni-TAP and Ni-TAA. Ni-TAP shows a two-dimensional sql network, while TAA is a twofold interpenetrated framework with an ffc topology. They both exhibit a high Brunauer−Emmett−Teller surface area (324 and 689 m 2 g −1 for Ni-TAP and Ni-TAA, respectively), a fairly good conductivity (1.57 × 10 −6 and 9.75 × 10 −5 S m −1 for Ni-TAP and Ni-TAA, respectively), and high chemical stability (a stable pH window of 1−14 for Ni-TAA). When applied in lithium metal batteries as an intermediate layer for guiding the uniform Li electrodeposition, Ni-TAP and Ni-TAA displayed impressive lithiophilicity and high Li-ion conductivity, enabling the achievement of smooth and dense Li deposition with a clear columnar morphology and stable Li plating/stripping behaviors with high Li utilization, which is anticipated to pave the way to upgrade Li metal anodes for application in high-energy-density battery systems.

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