Lu Zheng

Although zinc (Zn) deficiency severely inhibits rice growth, it remains unclear how melatonin (MT) promotes adaptation under conditions of insufficient Zn supply. To address this issue, rice seedlings were treated with MT, the NO donor sodium nitroprusside (SNP), or the NO scavenger c‐PTIO, alone or in combination, under Zn‐deficient conditions. Zn starvation rapidly promoted endogenous MT accumulation in rice roots, together with a 90.2%–179.5% rise in the transcript levels of MT biosynthetic genes. Exposure to Zn deprivation reduced root/shoot length and root/shoot biomass, by 46.2%/31.3% and 27.5%/39.6%, respectively. Among the tested concentrations, 10 μM MT produced the strongest protective effect, increasing root length, shoot height, root biomass, and shoot biomass by 59.9%, 34.2%, 21.7%, and 51.8%, respectively, relative to plants that were merely deficient in Zn. In Zn‐deficient plants, MT raised Zn concentration in root and shoot both by 16.2% and xylem sap Zn concentration by 15.6%. MT also increased root cell‐wall Zn content, pectin abundance, and pectin‐associated Zn by 20.0%, 39.3%, and 31.9%, respectively. At the expression level, MT moderated the induction of OsZIP4 , OsZIP5 , OsZIP8 , OsZIP9 , OsZIP10 , and OsHMA3 by Zn deficiency and further repressed OsZIP1 , implying feedback regulation of the Zn‐homeostasis network instead of direct activation of Zn‐transporter transcription. Root NO content rose by 29.8% after MT treatment, and SNP elicited increases in root and shoot Zn concentrations comparable to those associated with MT. Overall, the data suggest that an NO‐associated response contributes to MT‐mediated Zn‐deficiency tolerance by restoring Zn homeostasis, promoting apoplastic Zn remobilization and root‐to‐shoot transport, and limiting oxidative damage.

Iron (Fe) is indispensable for plant growth and development. Notably, melatonin (MT) serves as a key regulator to improve plant tolerance under nutrient stress conditions. Currently, the exact mechanism regulating MT's involvement in the rice Fe‐deficiency response remains to be elucidated. This study reveals that Fe‐deficiency stress triggers a rapid increase in endogenous MT levels in rice roots and induces the expression of MT synthesis‐related genes, underscoring the involvement of MT in the rice Fe‐starvation response. Exogenously applied MT rescues the root growth inhibition triggered by Fe deficiency and efficiently mitigates leaf chlorosis in rice. Mechanistically, MT decreases Fe retention in the root cell wall and its hemicellulose fraction, thereby promoting the remobilization of stored Fe and increasing soluble Fe content. Additionally, MT selectively reshapes the transport networks by robustly upregulating genes associated with Strategy II Fe acquisition and internal Fe transport—including Ferric Reductase Defective 3‐like 1 ( OsFRDL1 ), Iron‐related transcription factor 3 ( OsIRO3 ), Nicotianamine Aminotransferase 1 ( OsNAAT1 ), OsNAS1 , OsNAS2 , Yellow Stripe‐Like 2 ( OsYSL2 ), and OsYSL15 —to accelerate root‐to‐shoot Fe translocation. Notably, this enhanced internal Fe recycling partially improves the plant's Fe nutritional status, which is consistent with a systemic negative feedback response that partially attenuates the core Strategy I ferrous iron transporters (OsIRT1/2) along with root‐surface ferric reductase (FCR) activity and proton secretion. Moreover, nitric oxide (NO) acts as a pivotal downstream mediator in MT‐induced mitigation of the rice Fe‐starvation response. In conclusion, MT alleviates Fe deficiency in rice by promoting the remobilization of hemicellulose‐bound Fe and enhancing root‐to‐shoot Fe translocation in an NO‐dependent manner. These processes are accompanied by partial attenuation of root‐surface FCR activity, proton secretion, and OsIRT1 / 2 expression, revealing a coordinated adjustment between internal Fe reutilization and external Fe‐acquisition responses.

Ribosomal phosphoprotein P1 (RPP1) is an integral component of the P-protein stalk in the 60S subunit of eukaryotic ribosomes and is required for the efficient elongation of translation. Previously, Arabidopsis RPP1A was revealed to be involved in the regulation of seed size and seed storage protein accumulation. In this work, the seedling growth analysis shows that the knockout mutation of Arabidopsis RPP1A significantly promoted seedling growth, particularly in the shoots. The label-free quantitative proteomic analysis demonstrated that a total of 593 proteins were differentially accumulated between the germinating seeds of the wild-type Col-0 and rpp1a mutant. And these proteins were significantly enriched in the intracellular transport, nitrogen compound transport, protein transport, and organophosphate metabolic process. The abundance of proteins involved in the RNA and protein processing processes, including ncRNA processing and protein folding, were significantly increased in the rpp1a mutant. Mutation in RPP1A highlighted the effects on the ribosome, energy metabolism, and nitrogen metabolism. The abundance of enzymes involved in glycolysis and pyruvate mechanism was decreased in the germinating seeds of the rpp1a mutant. Whereas the processes of amino acid biosynthesis, protein processing in endoplasmic reticulum, and biosynthesis of cofactors were enhanced in the germinating seeds of the rpp1a mutant. Taken together, the lack of RPP1A triggered changes in other ribosomal proteins, and the higher amino acid contents in the seedlings of the rpp1a mutant probably contributed to enhanced biosynthesis, processing, and transport of proteins, resulting in accelerated growth. Our results show the novel role of a P-protein and shed new light on the regulatory mechanism of seedling growth.

Beyond the role of a nutrient reservoir during germination, the endosperm of wheat seeds also responds to different abiotic stresses via modification of th

Nitrogen deficiency usually occurs along with aluminum toxicity in acidic soil, which is one of the major constraints for wheat production worldwide. In order to compare adaptive processes to N deficiency with different Al-tolerant wheat cultivars, we chose Atlas 66 and Scout 66 to comprehensively analyze the physiological responses to N deficiency, coupled with label-free mass spectrometry-based proteomics analysis. Results showed that both cultivars were comparable in most physiological indexes under N deficient conditions. However, the chlorophyll content in Scout 66 was higher than that of Atlas 66 under N deficiency. Further proteomic analysis identified 5592 and 5496 proteins in the leaves of Atlas 66 and Scout 66, respectively, of which 658 and 734 proteins were shown to significantly change in abundance upon N deficiency, respectively. The majority of the differentially expressed proteins were involved in cellular N compound metabolic process, photosynthesis, etc. Moreover, tetrapyrrole synthesis and sulfate assimilation were particularly enriched in Scout 66. Our findings provide evidence towards a better understanding of genotype-dependent responses under N deficiency which could help us to develop N efficient cultivars to various soil types.

DNA assembly is an essential technique enabling metabolic engineering and synthetic biology. Combining novel DNA assembly technologies with rational metabolic engineering can facilitate the construction of microbial cell factories. Amino acids and derived biochemicals are important products in industrial biotechnology with wide application and huge markets. DNA assembly scenarios encountered in metabolic engineering for the construction of amino acid and related compound producers, such as design-build-test-learn cycles, construction of precise genetic circuits and repetitive DNA molecules, usually require for iterative, scarless and repetitive sequence assembly methods, respectively. Restriction endonuclease (RE)-assisted strategies constitute one of the major categories of DNA assembly. Here, we developed a Type IIP and IIS RE-assisted method named PS-Brick that comprehensively takes advantage of the properties of PCR fragments and REs for iterative, seamless and repetitive sequence assembly. One round of PS-Brick reaction using purified plasmids and PCR fragments was accomplished within several hours, and transformation of the resultant reaction product from this PS-Brick assembly reaction exhibited high efficiency (104–105 CFUs/µg DNA) and high accuracy (~ 90%). An application of metabolic engineering to threonine production, including the release of feedback regulation, elimination of metabolic bottlenecks, intensification of threonine export and inactivation of threonine catabolism, was stepwise resolved in E. coli by rounds of “design-build-test-learn” cycles through the iterative PS-Brick paradigm, and 45.71 g/L threonine was obtained through fed-batch fermentation. In addition to the value of the iterative character of PS-Brick for sequential strain engineering, seamless cloning enabled precise in-frame fusion for codon saturation mutagenesis and bicistronic design, and the repetitive sequence cloning ability of PS-Brick enabled construction of tandem CRISPR sgRNA arrays for genome editing. Moreover, the heterologous pathway deriving 1-propanol pathway from threonine, composed of Lactococcus lactis kivD and Saccharomyces cerevisiae ADH2, was assembled by one cycle of PS-Brick, resulting in 1.35 g/L 1-propanol in fed-batch fermentation. To the best of our knowledge, the PS-Brick framework is the first RE-assisted DNA assembly method using the strengths of both Type IIP and IIS REs. In this study, PS-Brick was demonstrated to be an efficient DNA assembly method for pathway construction and genome editing and was successfully applied in design-build-test-learn (DBTL) cycles of metabolic engineering for the production of threonine and threonine-derived 1-propanol. The PS-Brick presents a valuable addition to the current toolbox of synthetic biology and metabolic engineering.