Zhanhui Wu

Nitrate (NO ₃ ^- ) plays dual roles in vascular plants, functioning as both an essential macronutrient and a phytoactive signaling compound. Research indicates that the high-affinity NO ₃ ^- transporter OsNRT2.3b orchestrates fundamental agronomic traits, including biomass accumulation, grain production, and nitrogen (N) metabolism efficiency in cultivated rice. In this study, transgenic lettuce lines of OsNRT2.3b were generated, from which four lines with high OsNRT2.3b expression (OE20−5, OE21−7, OE21−11, and OE21−13) were selected and subjected to normal (CK) and low nitrogen (LN) treatments for 12 d. The results indicate that OsNRT2.3b transgenosis increased chlorophyll and glutathione (GSH) contents, as well as the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), in lettuce. However, OsNRT2.3b transgenosis had little effect on certain agronomic traits (leaf number, plant height, and leaf dimensions) of lettuce. Compared to the wild-type (WT), OsNRT2.3b transgenosis substantially enhanced the contents of NO ₃ ^- , ammonium (NH ₄ ⁺ ), amino acids, soluble protein, and the activities of NO ₃ ^- reductase (NR), nitrite (NO ₂ ^- ) reductase (NiR), glutamine synthetase (GS), and glutamate synthetase (GOGAT) in lettuce. Thus, OsNRT2.3b transgenosis improves the antioxidant capacity, photosynthetic level, and N use efficiency of lettuce. This research provides theoretical references for improving the N utilization efficiency of lettuce and enhancing its antioxidant capacity.

Phosphorus (P) is a limiting nutrient for plant growth and productivity. Improving P use efficiency is important for crop production. In Lactuca sativa (lettuce), five phosphate starvation response 1 (PHR1) genes were identified and characterized through a bioinformatics approach. The expression patterns of LsaPHR1s were examined using qRT-PCR under various treatments, including devoid phosphorus (DP), low phosphorus (LP), high phosphorus (HP), darkness, ABA, IAA, and MeJA. The results indicate that LsaPHR1s in lettuce responded to phosphorus stress, hormones, and darkness. Furthermore, we engineered LsaPHR1.1 knock-out mutants via CRISPR/Cas9-mediated genome editing. Then, the mutants were subjected to phosphorus stress (DP, LP, and HP). In contrast to WT, the mutants improved nitrate and ammonium contents, increased antioxidant enzyme activity, and elevated antioxidant and chlorophyll contents. Our results offer a potential strategy for improving phosphorus stress tolerance in lettuce, which holds great significance for maintaining yield and quality.

Calcium is one of the essential elements for plant growth, and its deficiency can easily lead to tipburn. ACA/ECA is a crucial protein involved in calcium transport in plants. In this study, we utilized bioinformatics methods to identify and analyze members of the ACA/ECA gene family in lettuce. The functions of certain ACA/ECA genes in lettuce were preliminary validated using TRV-VIGS. In this study, 18 members belonging to lettuce ACA/ECA family were identified, unveiling a certain level of conservation in their evolutionary relationships. They are unevenly distributed across eight chromosomes, with six pairs of genes displaying collinear relationships. Among these 18 members, differences exist in molecular weight, number of amino acids, theoretical isoelectric point, overall average hydrophilicity, and instability coefficient. Although there are significant variations in the number of exons, the count remains relatively consistent within the same clade of ACA/ECA genes. A total of 21 pairs of ACA/ECA genes exhibit collinearity between lettuce and Arabidopsis. The lettuce ACA/ECA gene family encompasses a diverse array of light-responsive, hormone-responsive, and anaerobic-inducible elements. The expression levels of the LsaACA2, LsaACA10, and LsaACA11 genes in the leaves of lettuce are notably high. Individually silencing these genes resulted in a decrease in calcium content in leaves and exacerbated the symptoms of tipburn. The above results establish a foundation for the further exploration of ACA/ECA gene functions in lettuce and offer a theoretical basis for mitigating the occurrence of tipburn in lettuce leaves.

Pepper (Capsicum annuum L.) is a popular vegetable in people’s daily lives. During pepper growth, calcium (Ca) is an essential macronutrient, and calcium-transporting ATPase (ACA/ECA) is a vital protein for calcium transport. However, reports on the ACA/ECA gene family in the pepper genome are lacking. Hence, we used various bioinformatics methods to identify the ACA/ECA gene family in pepper. We identified eleven CaACA/ECA-family genes in pepper. The chromosomal distribution, phylogenetic evolution, characteristics, gene collinearity, gene and protein structures, cis-acting elements, and specific expression patterns of CaACA/ECAs were analyzed, revealing evolutionary relationships and correlations between CaACA/ECAs and other species (Arabidopsis, rice, and tomato). The experimental results indicate that CaACA/ECAs are stable and hydrophobic proteins, with each of the eleven CaACA/ECA proteins containing all ten motifs. Eleven CaACA/ECA genes are unevenly distributed on the eight chromosomes, and they substantially differ in the number of exons. We found a close correlation between the ACA/ECAs of pepper, Arabidopsis, and tomato. The CaACA/ECA genes contain various plant-hormone-, growth-, and stress-related cis-acting elements. The qRT-PCR results indicate that the expression levels of the eleven CaACA/ECAs exhibit differential temporal expression patterns under various exogenous Ca²⁺ concentrations. These results provide a theoretical basis for further studying the function of the pepper ACA/ECA gene family and valuable information for identifying and screening genes for pepper stress tolerance breeding.

Ascorbic acid (AsA) is an essential nutritional component and powerful antioxidant in vegetables, and in plants, AsA levels are regulated by light. AsA levels in the leaves of Chinese chive (Allium tuberosum Rottler ex Spr), a popular vegetable, are poorly understood. Thus, this study was performed to assess the influence of light on AsA biosynthesis in chive and select related genes (AtuGGP1 and AtuGME1); in addition, bioinformatic analyses and gene expression level assays were performed. The biological information obtained for AtuGGP1 and AtuGME1 was analysed with several tools, including NCBI, DNAMAN, and MEGA11. After different light treatments were performed, the Chive AsA content and AtuGGP1 and AtuGME1 expression levels were determined. These results suggest that 1) compared with natural light, continuous darkness inhibited AsA synthesis in chives. 2) The amino acid sequences of AtuGGP1 and AtuGME1 are very similar to those of other plants. 3) The trends observed for the expression levels of AtuGGP1 and AtuGME1 were consistent with the AsA content observed in chives. Hence, we speculated that light controls AsA biosynthesis in chives by regulating AtuGGP1 and AtuGME1 expression. This study provided impactful and informative evidence regarding the functions of GGP and GME in chives.

Environmental stressors such as salinity have pronounced impacts on the growth, productivity, nutrition, and flavor of horticultural crops, though yield loss sometimes is inevitable. In this study, the salinity influences were evaluated using hydroponic Chinese chive (Allium tuberosum) treated with different concentrations of sodium chloride. The results demonstrated that lower salinity could stimulate plant growth and yield. Accordingly, the contents of soluble sugar, ascorbic acid, and soluble protein in leaf tissues increased, following the decrease of the nitrate content, under mild salinity (6.25 or 12.5 mM NaCl). However, a higher level of salinity (25 or 50 mM NaCl) resulted in growth inhibition, yield reduction, and leaf quality deterioration of hydroponic chive plants. Intriguingly, the chive flavor was boosted by the salinity, as evidenced by pungency analysis of salinity-treated leaf tissues. UPLC-MS/MS analysis reveals that mild salinity promoted the accumulation of glutamic acid, serine, glycine, and proline in leaf tissues, and thereby enhanced the umami and sweet flavors of Chinese chive upon salinity stress. Considering the balance between yield and flavor, mild salinity could conduce to hydroponic Chinese chive cultivation. Transcriptome analysis revealed that enhanced pungency could be ascribed to a salt stress-inducible gene, AtuFMO1, associated with the biosynthesis of S-alk(en)yl cysteine sulphoxides (CSOs). Furthermore, correlation analysis suggested that two transcription factors, AtubHLH and AtuB3, were potential regulators of AtuFMO1 expressions under salinity. Thus, these results revealed the molecular mechanism underlying mild salinity-induced CSO biosynthesis, as well as a practical possibility for producing high-quality Chinese chive hydroponically.

Chinese chive (Allium tuberosum) is widely cultivated around the world for its unique flavor, nutrient, and medicinal values, yet its molecular mechanism on flavor formation and other metabolic pathways remains intangible. The elucidation of these complex processes begins with investigating the expression of the genes of interest, however the appropriate reference genes (RGs) for normalizing the gene expression are still unavailable in A. tuberosum. To fill this lacuna, transcriptome-wide screening was undertaken to identify the most stable genes according to the analysis of their FPKM values. The expression stability of the RGs was further evaluated using geNorm, NormFinder, BestKeeper, and RefFinder algorithms. The comprehensive analysis showed that GLY1 and SKP1, instead of two traditionally used RGs (eIF1α and ACT2), were the most stable genes across diverse A. tuberosum tissues, indicating the necessity to carefully validate the stability of RGs prior to their use for normalizations. As indicated by geNorm, the normalizations with at least two RGs could give more accurate results. qRT-PCR experiments were conducted with randomly selected genes, demonstrating that normalization with a combination of GLY1 and SKP1 resulted in reliable normalization results. Our finding represents the first attempt toward establishing a standardized qRT-PCR analysis in this economically important vegetable.

Seedling overgrowth always develops in undernourished plants due to biotic or abiotic stresses, which significantly decrease the yield of crops and vegetables. It is known that the plant growth retardants paclobutrazol (PBZ) and chlormequat chloride (CCC) are the most commonly used chemicals in controlling seedling height in plants by regulating the gibberellin (GA) biosynthesis pathway. However, the exact molecular regulation mechanism remains largely unknown. This study performed a comprehensive transcriptome profile to identify significantly differentially expressed genes after adding CCC and PBZ to the water culture seedling raising system for the first time. According to the obviously restrained shoots and roots, the GA biosynthesis genes were significantly decreased, as well as the endogenous GA content being reduced. Intriguingly, the GA signaling pathway genes were affected in opposite ways, increasing in roots but decreasing in shoots, especially regarding the phytochrome interacting factor SlPIF1 and the downstream genes expansins (SlEXPs), which promote cell wall remodeling. Further study found that the most down-regulated genes SlEXPA5 and SlEXPA15 were expressed specifically in shoot tissue, performing the function of repressing elongation, while the up-regulated genes SlEXPB2 and SlEXPB8 were proven to be root-specific expressed genes, which may promote horizontal elongation in roots. This research reported the comprehensive transcriptome profiling of plant growth retardants in controlling seedling overgrowth and restraining GA biosynthesis through the regulation of the GA signaling-related genes SlPIF1 and SlEXPs, with an opposite expression pattern between roots and shoots.