Polyaspartic acid (PASP) is a macromolecule compound with carboxylic acid side chains which is polymerized by L-aspartic acid, has been used as a biodegradable and environmentally-friendly chelating agent to enhance the phytoremediation of heavy metal-contaminated soils. Cadmium (Cd) is a toxic element for plant growth, productivity, and food security. To reveal the responses of PASP to plant physiology and morphology under Cd stress, we comprehensively analyzed soil characteristics, cell ultrastructure, reactive oxygen species (ROS), antioxidant enzymes, Cd uptake, transport, subcellular distribution, cell wall compositions, and their Cd chelating capacity in rapeseed. The results showed PASP increased the content of total N, total P, and available P in soil by 3.4%, 28.6%, and 39.8%, respectively, but did not change soil pH and available Cd. Meanwhile, PASP promoted dry mass accumulation and increased photosynthetic pigment content in rapeseed leaves by maintaining the chloroplast structure. Lower malondialdehyde (MDA) content and hydrogen peroxide (H₂O₂) accumulation and activated antioxidant enzymes in leaves indicate that PASP contributed to relieving Cd-induced oxidative damage to cells of rapeseed leaves. The results indicated that PASP application increased the Cd distribution ratio in root cell walls from 47.4% to 62.3% and decreased the Cd content in xylem sap by 37.8%, which ultimately reduced Cd reallocation in leaves. Additionally, higher pectin content and Cd in pectin resulted in higher Cd retention in leaf cell walls while reducing its concentration in the organelle fraction. The results indicated that 0.3% PASP effectively alleviated Cd stress in rapeseed leaves by inhibiting Cd transportation from roots, activating antioxidant enzymes to scavenge ROS, and promoting Cd chelation by cell wall pectin in leaves.

CCCH zinc finger proteins contain one to six tandem CCCH motifs composed of three cysteine and one histidine residues and have been widely found in eukaryotes. Plant CCCH proteins control a wide range of developmental and adaptive processes through DNA–protein, RNA–protein and/or protein–protein interactions. The complex networks underlying these processes regulated by plant CCCH proteins are often involved in phytohormones as signal molecules. In this review, we described the evolution of CCCH proteins from green algae to vascular plants and summarized the functions of plant CCCH proteins that are influenced by six major hormones, including abscisic acid, gibberellic acid, brassinosteroid, jasmonate, ethylene and auxin. We further compared the regulatory mechanisms of plant and animal CCCH proteins via hormone signaling. Among them, Arabidopsis AtC3H14, 15 and human hTTP, three typical CCCH proteins, are able to integrate multiple hormones to participate in various biological processes.

Tobacco is an important cash crop in China, but the low potassium (K) content and high ratio of total sugar to nicotine in tobacco leaves have seriously affected the quality of tobacco leaves. As a fertilizer synergist, polyaspartic acid (PASP) can improve the K content in tobacco leaves, but it is unknown how it affects the K content in different parts of tobacco leaves, and how PASP affects the ratio of total sugar to nicotine in tobacco leaves has not been reported. Therefore, “Zhongyan 100” was selected for pot experiments with 5 different PASP addition levels: CK (0.0 %), P1 (0.1 %), P2 (0.2 %), P3 (0.4 %) and P4 (0.6 %), to reveal the effects of PASP on tobacco growth, K content, sugar content, nicotine content and the ratio of total sugar to nicotine in different tobacco parts, and determine the optimal PASP dosage for regulating the K content and the ratio of total sugar to nicotine in tobacco. The results showed that P1 (0.1 %) and P2 (0.2 %) only had slighter effects on tobacco growth and quality, while P3 (0.4 %) and P4 (0.6 %)treatments significantly promoted dry matter accumulation, increased K and nicotine content in leaves, decreased reducing sugar and total soluble sugar content in leaves, thereby reducing the ratio of total sugar to nicotine in tobacco leaves, especially in upper leaves. Considering the economic cost savings, 0.4% PASP was determined as the best application level to improve the growth and quality of tobacco. Thus, proper application of PASP is beneficial to improve tobacco leaf quality and reduce chemical K fertilizer application, thereby decreasing agricultural environmental risks of chemical fertilizer and alleviating the rapid depletion of potash in the world.