LcSABP2, a salicylic acid binding protein 2 gene from Lycium chinense, confers resistance to triclosan stress in Nicotiana tabacum

Computational and experimental identification of an exceptionally efficient ethyl ester synthetase with broad substrate specificity and high product yield, suggests potential for industrial biocatalysis

Transesterification plays a crucial role in the synthesis of diverse esters in organic synthesis but is barely reported in biocatalysis. Here, we computationally identify the salicylic acid-binding protease 2 (SABP2) as an efficient ethyl ester bond synthetase by QM/MM MD and free energy simulations and present the practical and effective utilization of SABP2 as an eco-friendly biocatalyst for transesterification reactions by a series of experiments. Our findings demonstrate that SABP2 efficiently catalyzes the transesterification reaction between the carboxyl acid group of promiscuous aromatic substrates and ethanol to produce the corresponding ethyl esters. Notably, while SABP2 exhibits its native capability to catalyze the hydrolysis of the methyl salicylate (MeSA), the transesterification rate (producing ethyl salicylate, EtSA) is about 3500 times higher than the hydrolysis rate. Additionally, a range of aromatic methyl esters are employed in the transesterification process, resulting in high yields (up to 98.9 %) of the corresponding ethyl esters. These results indicate a broad substrate scope for SABP2-catalyzed transesterification reactions, demonstrating its potential as a valuable biocatalyst for ester synthesis in industry.

Critical review on the environmental behaviors and toxicity of triclosan and its removal technologies

As a highly effective broad-spectrum antibacterial agent, triclosan (TCS) is widely used in personal care and medical disinfection products, resulting in its widespread occurrence in aquatic and terrestrial environments, and even in the human body. Notably, the use of TCS surged during the COVID-19 outbreak, leading to increasing environmental TCS pollution pressure. From the perspective of environmental health, it is essential to systematically understand the environmental occurrence and behavior of TCS, its toxicological effects on biota and humans, and technologies to remove TCS from the environment. This review comprehensively summarizes the current knowledge regarding the sources and behavior of TCS in surface water, groundwater, and soil systems, focusing on its toxicological effects on aquatic and terrestrial organisms. Effluent from wastewater treatment plants is the primary source of TCS in aquatic systems, whereas sewage application and/or wastewater irrigation are the major sources of TCS in soil. Human exposure pathways to TCS and associated adverse outcomes were also analyzed. Skin and oral mucosal absorption, and dietary intake are important TCS exposure pathways. Reducing or completely degrading TCS in the environment is important for alleviating environmental pollution and protecting public health. Therefore, this paper reviews the removal mechanisms, including adsorption, biotic and abiotic redox reactions, and the influencing factors. In addition, the advantages and disadvantages of the different techniques are compared, and development prospects are proposed. These findings provide a basis for the management and risk assessment of TCS and are beneficial for the application of treatment technology in TCS removal.

Salicylic acid interacts with other plant growth regulators and signal molecules in response to stressful environments in plants

Salicylic acid (SA) is one of the potential plant growth regulators (PGRs) that regulate plant growth and development by triggering many physiological and metabolic processes. It is also known to be a crucial component of plant defense mechanisms against environmental stimuli. In stressed plants, it is documented that it can effectively modulate a myriad of metabolic processes including strengthening of oxidative defense system by directly or indirectly limiting the buildup of reactive nitrogen and oxygen radicals. Although it is well recognized that it performs a crucial role in plant tolerance to various stresses, it is not fully elucidated that whether low or high concentrations of this PGR is effective to achieve optimal growth of plants under stressful environments. It is also not fully understood that to what extent and in what manner it cross-talks with other potential growth regulators and signalling molecules within the plant body. Thus, this critical review discusses how far SA mediates crosstalk with other key PGRs and molecular components of signalling pathways mechanisms, particularly in plants exposed to environmental cues. Moreover, the function of SA exogenously applied in regulation of growth and development as well as reinforcement of oxidative defense system of plants under abiotic stresses is explicitly elucidated.

Identification of yield-related genes through genome-wide association: case study of weeping forsythia, an emerging medicinal crop

KEY MESSAGE

This study identified candidate genes related to fruit yield for an emerging medicinal crop, weeping forsythia.

BACKGROUND

The genetic basis of crop yield is an agricultural research hotspot. Identifying the genes related to yield traits is the key to increase the yield. Weeping forsythia is an emerging medicinal crop that currently lacks excellent varieties. The genes related to fruit yield in weeping forsythia have not been identified.

OBJECTIVE

Thus, we aimed to screen the candidate genes related to fruit yield of weeping forsythia by using genome-wide association analysis.

METHODS

Here, 60 samples from the same field and source of weeping forsythia were collected to identify its yield-related candidate genes. Association analysis was performed on the variant loci and the traits related to yield, i.e., fruit length, width, thickness, and weight.

RESULTS

Results from admixture, neighbor-joining, and kinship matrix analyses supported the non-significant genetic differentiation of these samples. Significant association was found between 2 variant loci and fruit length, 8 loci and fruit width, 24 loci and fruit thickness, and 13 loci and fruit weight. Further search on the 20 kb up/downstream of these variant loci revealed 1 gene related to fruit length, 16 genes related to fruit width, 12 genes related to fruit thickness, and 13 genes related to fruit weight. Among which, 4 genes, namely, WRKY transcription factor 35, salicylic acid-binding protein, auxin response factor 6, and alpha-mannosidase were highly related to the fruit development of weeping forsythia.

CONCLUSION

This study identify four candidate genes related to fruit development, which will provide useful information for the subsequent molecular-assisted and genetic breeding of weeping forsythia.

Mechanism of growth amelioration of triclosan-stressed tobacco (Nicotiana tabacum) by endogenous salicylic acid

Among emerging organic contaminants (EOCs), triclosan (TCS) is an antibacterial agent and frequently detected in sludge. In this study, RNA sequencing (RNA-seq) was used to obtain the first transcriptomic profile of tobacco with TCS treatment in comparison with control. The results of transcriptome profiling indicated that salicylic acid (SA) signalling pathway actively participated in the tobacco's response to TCS treatment. The accumulation of endogenous SA in transgene tobacco lines transformed with a homologous gene of SA binding protein (LcSABP) was significantly enhanced. The resistance of transgenic tobacco lines to TCS was markedly enhanced revealed by morphological and physiological indexes while the total Chl level and Pn of transgenic individuals showed about 180% and 250% higher than that of WT on average, and the accumulation of H2O2 and O2- induced by TCS in SABP overexpressing tobacco was 35.3%-37.3% and 53.0%-56.0% lower than that of WT. In order to further explore the mechanism of TCS tolerance in transgenic plants, RNA-seq was then performed to obtain the second transcriptomic profile between wild type and transgenic samples with TCS exposure. The results indicated that differentially expressed genes (DEGs) were most highly enriched in MAPK signalling pathway, amino acid synthesis pathway and plant hormone transduction pathway. Especially, genes encoding key proteins such as cytochrome P450, laccase, peroxidase, glycosyl transferase, glutathione S-transferase and ATP-binding cassette were considered to be related to the increased tolerance ability of transgenic tobacco to the treatment of TCS stress. This research will likely provide novel insights into the molecular mechanism of SA-mediated amelioration of TCS stress on tobacco.

Klebsiella sp. PD3, a phenanthrene (PHE)-degrading strain with plant growth promoting properties enhances the PHE degradation and stress tolerance in rice plants

Phenanthrene (PHE) is harmful to human health and is difficult to be eliminated from environment. In this study, an aerobic bacterium capable of use PHE as a sole carbon source and energy was isolated and classified as Klebsiella sp. PD3 according to 16S rDNA analysis. The degradation efficiency of PHE reached to about 78.6% after 12 days of incubation with strain PD3. Identification of metabolites formed during PHE degradation process by this strain was carried out by GC-MS. The first degradation step of PHE by PD3 was proposed to generate 1-hydroxy-2-naphthoic acid. Two subsequent different routes for the metabolism of 1-hydroxy-2-naphthoic acid were proposed. Strain PD3 also showed two plant growth promoting properties like phosphate solubilization and ACC deaminase activity. Inoculation with Klebsiella sp. PD3 significantly improved growth performance, biomass production, seed germination rate, photosynthetic capacity, antioxidant levels, relative water content and chlorophyll accumulation in rice (Oryza sativa L.) plants under PHE stress conditions in comparison with non-inoculation treatment. Moreover, PD3-inoculated rice showed lower ROS accumulation, ethylene production, ACC content, ACC oxidase activity and electrolyte leakage under PHE treatment compared to non-inoculated ones. The combination use of rice plants and strain PD3 was also shown to enhance the removal efficiency of PHE from the soil and decline the PHE accumulation in plants. Synergistic use of plants and bacteria with PHE degradation ability and PGPR attributes to remediate the PHE-contaminated soil will be an important and effective way in the phytoremediation of PHE-contaminated soils.