Accumulation of cadmium (Cd) ions in soil is an increasingly acute ecological problem in agriculture production. Selenium nanoparticles (SeNPs) can mediate Cd tolerance in plants; however, the underlying mechanisms remain unclear. Herein, we show that the foliar application of SeNPs improved the adaptive capacity of tomato plants to decrease Cd-induced damage. SeNPs induced more Cd in roots but not in shoots despite greater accumulation of selenium and sulfur in both tissues and high selenate influx. Additionally, SeNPs significantly increased thiol compounds, including glutathione, cysteine, and phytochelatins, contributing to enhanced Cd detoxification. Importantly, SeNPs induced the expression of sulfate transporters 1:3, S-adenosylmethionine 1 and polyamine transporter 3. Then, experiments with mutants of these genes showed that SeNP-reduced Cd stress largely relies on the levels and shoot-to-root transport of selenium/sulfur and polyamines. These findings highlight the potential of SeNPs to improve crop production and phytoremediation in heavy metal-contaminated soils.

Salvia miltiorrhiza-derived carbon dots (SmCDs), as a new type of nanomaterial, play vital roles in plant growth, antioxidation and abiotic stress alleviation. Flowering Chinese cabbage is prone to wilt and yellowing after harvest. However, the roles of SmCDs in delaying senescence of postharvest flowering Chinese cabbage to maintain quality remain unclear. Herein, we found that SmCDs had effective impacts on anti-aging, enhancing maximal fluorescence ratio, procrastinating chlorophyll degradation, sustaining reactive oxygen species (ROS) metabolism homeostasis, and improving the contents of vitamin C, sucrose, soluble sugar, and flavonoid. Moreover, SmCDs suppressed the expressions of chlorophyll degradation genes (BrNYE1, BrNYC1, BrNOL, BrPPH, and BrPAO), senescence marker gene (BrSAG12), and respiratory burst oxidase homologs genes (BrRBohA, BrRBohB, BrRBohD, and BrRBohF), while SmCDs promoted the flavonoid biosynthesis genes (BrFLS3, BrFLS1, BrC4H, and BrCHI) expression. Interestingly, sucrose synthase, neutral invertase, and acid invertase might be the pivotal enzymes to restrict sugar accumulation under SmCDs treatment.

Iron (Fe) plays an important role in the growth and development of plants. The effects of different Fe concentrations, 1-aminocyclopropane-1-carboxylic acid (ACC), and cobalt chloride (Co²⁺) treatments on plant growth, quality and the adaptive response to Fe deficiency stress were investigated in flowering Chinese cabbage. The results revealed that Fe deficiency stress inhibited plant growth. The contents of vitamin C, soluble protein, and soluble sugar in leaves and stalks were significantly reduced under Fe deficiency stress, while the content of cellulose and nitrate was increased. Fe deficiency stress clearly reduced the net photosynthetic rate and nitrate reductase activity in the leaves. The balance system of active oxygen metabolism was destroyed due to Fe deficiency, resulting in the decrease in catalase activity, superoxide dismutase activity of roots and leaves, and peroxidase (POD) activity of leaves, while POD activity in roots and malonaldehyde content in roots and leaves were significantly increased. The treatments of Fe deficiency and ACC significantly reduced the pH value of the root medium, promoted the release of ethylene, and increased Fe³⁺ reductase activity, while Co²⁺ treatment showed results that were the opposite to those of Fe deficiency and ACC treatments. Thus, Fe deficiency stress affected nitrogen metabolism, photosynthesis, reactive oxygen metabolism, pH of root medium, and Fe³⁺ reductase activity, which was related to physiological adaptive response and tolerance mechanisms. We also found that ethylene could be involved in regulating the adaptive response to Fe deficiency stress in flowering Chinese cabbage.

In this study, we demonstrate and elucidate how spermidine carbon dots (Spd-CDs) enhance tomato tolerance under heat stress (45 °C).

Flowering Chinese cabbage is prone to withering, yellowing and deterioration after harvest. Melatonin plays a remarkable role in delaying leaf senescence and increasing flavonoid biosynthesis. However, the underlying molecular mechanisms of melatonin procrastinating postharvest senescence by regulating flavonoid biosynthesis remain largely unknown. In this study, melatonin could promote flavonoid accumulation and delay the postharvest senescence of flowering Chinese cabbage. Surprisingly, we observed that BrFLS1 and BrFLS3.2 were core contributors in flavonoid biosynthesis, and BrERF2 and BrERF109 were crucial ethylene response factors (ERFs) through the virus-induced gene silencing (VIGS) technique, which is involved in regulating the postharvest senescence under melatonin treatment. Furthermore, yeast one-hybrid (Y1H), dual luciferase (LUC), and β-glucuronidase (GUS) tissue staining experiments demonstrated that BrERF2/BrERF109 negatively regulated the transcripts of BrFLS1 and BrFLS3.2 by directly binding to their promoters, respectively. Silencing BrERF2/BrERF109 significantly upregulated the transcripts of BrFLS1 and BrFLS3.2, promoting flavonoid accumulation, and postponing the leaf senescence. Our results provided a new insight into the molecular regulatory network of melatonin delaying leaf senescence and initially ascertained that melatonin promoted flavonoid accumulation by suppressing the inhibition of BrERF2/BrERF109 on the transcripts of BrFLS1 and BrFLS3.2, which led to delaying the leaf senescence of postharvest flowering Chinese cabbage.

The polyamine uptake transporter (Put), an important polyamines-related protein, is involved in plant cell growth, developmental processes, and abiotic stimuli, but no research on the Put family has been carried out in the tomato. Herein, eight tomato Put were identified and scattered across four chromosomes, which were classified into three primary groups by phylogenetic analysis. Protein domains and gene structural organization also showed a significant degree of similarity, and the Put genes were significantly induced by various hormones and polyamines. Tissue-specific expression analysis indicated that Put genes were expressed in all tissues of the tomato. The majority of Put genes were induced by different abiotic stresses. Furthermore, Put2 transcription was found to be responsive to salt stress, and overexpression of Put2 in yeast conferred salinity tolerance and polyamine uptake. Moreover, overexpression of Put2 in tomatoes promoted salinity tolerance accompanied by a decrease in the Na⁺/K⁺ ratio, restricting the generation of reactive oxygen and increasing polyamine metabolism and catabolism, antioxidant enzyme activity (SOD, CAT, APX, and POD), and nonenzymatic antioxidant activity (GSH/GSSG and ASA/DHA ratios, GABA, and flavonoid content); loss of function of put2 produced opposite effects. These findings highlight that Put2 plays a pivotal role in mediating polyamine synthesis and catabolism, and the antioxidant capacity in tomatoes, providing a valuable gene for salinity tolerance in plants.